I’m a lifelong student of pruning. I LOVE learning, observing, and theorizing over tree physiology and applying newfound thoughts and theories with curiosity and gratitude every pruning season. Earlier this week, I saw yet another article talking negatively about heart rot, which motivated me to finally finish my essay on the subject. In this essay I’ll talk positively about heart rot, tree physiology, pruning and orchard ecology.
“That’s heart rot. The tree’s health is in decline” replied one horticulturalist to the above photo. “Hey, that’s heart rot…you had better apply a fungicide spray” replied someone else. And my response? Have you ever pruned an old tree?!
When it comes to pruning, I almost exclusively work with old trees and I see this a lot. Yes, it’s heart rot. No, I do not believe this tree is in imminent danger or even in decline, which is surprisingly a stance that not many people take. And so we’ll start there.
What is heart rot? Heart rot is what happens when the pith of a tree (the center) starts to decay. The instigators of this core decay are fungi that get into the heartwood through wounds, broken branches, pruning cuts, etc. In a healthy tree, they only stay in the heartwood, which is the part of the tree that is not considered alive. It is often thought of as the dumping grounds for the tree, where minerals and older tree rings go to rest.
As fungi gradually work their way through the heartwood, the tree becomes hollow over time. In the timber realm, these fungi are considered harmful pathogens because they reduce the value of a log. Hollow logs= less money. This way of thinking, that fungi are harmful pathogens and hollow is unsaleable, somehow worked its way into horticulture, only this time… Fungi= harmful, Hollow=structurally unsound/sick/dying. So very rarely have I seen someone in the horticultural realm step back on the subject of heart rot to see the forest for the trees, which is why I’m writing this essay.
What is heart rot doing to the tree? Way back in 2007, when I was doing a lot of forest inventory in Louisiana, I had to core all sorts of trees in order to assess their health and age. Often, after removing the core, I’d get sprayed with stinky water, spurted with methane from the hole I created, or witness a mass evacuation of insects. Lots of life inhabited those trees and that’s because heart rot fungi slowly made way for life to be there. This concept of rot-makes-habitat was really hammered home when I helped a USDA sniper tranq some inbreeding black bears that had chosen to calve in the cavities of old cypress trees. Straight up Winnie-the-Pooh habitat, those cypress swamps. Only poor Winnie was shacking up with his cousin in this scenario and had to move.
Fast forward 11 years to 2018, when I flew to Basque France to attend a conference on pollarding. It was there, surrounded by European foresters, forest engineers and horticulturalists, that everyone had a special place in their soul for heart rot and hollow trees, something I had never encountered before. A prevailing opinion, which I now view as a bridge between forest ecology and horticulture, was that heart rot creates hollows/habitats for all sorts of fauna. In hosting this fauna, the trees become collectors of poo (feces, not the bear). This creates an incredible microbial metabolism in the tree which, when combined with decomposing heartwood full of trapped minerals, supplies a steady amount of organic fertilizer that is slowly released to the base of the tree. Since trees store growth rings in the heartwood on an annual basis, this natural process of decomposition and fertilizing is a renewable. Hollow trees provide their own compost. That’s true sustainability.
But isn’t a hollow tree a weakened tree? The comparison I always see is that heart rot or hollowing makes the tree structurally unsound. I’m here to tell you that this is mostly an emotional reaction. In all reality (and some physics), the tree isn’t weakened at all until the trunk’s radius is 70% hollow1.
And keep in mind, that’s an un-pruned forest tree with a full crown. If the tree is pruned to allow for airflow and to correct for weight imbalances, the hollow tree is much more structurally sound. An old pollarded willow tree, for example, boasts complete structural soundness until the trunk’s radius is 93% hollow2 thanks to a radically reduced crown . This tells me that mostly hollow orchard trees (on good root systems. Eff dwarfing trees), if pruned regularly, pose very little structural threat.
What causes a hollow tree to ultimately fail? When trees are hollow and the wind has a strong influence over them (most likely due to crown size and density), the circular trunk becomes a bit oblong. This creates a vertical crack, which is the ultimate shearing stress for the tree. Again, pruning for crown reduction in old trees really helps to avoid the development of these shear cracks.
More explained through tree physiology. Here’s the deal. Trees contain both sapwood and heartwood (see tree cross section picture at beginning of essay). The sapwood is the outer, living, layer of the tree that is responsible for carrying water and nutrients up to the canopy. Think of it as a bunch of tubes, or vessels (xylem), constituting the lifeline of the tree. Since this is one of the most important parts of the tree, it’s a heavy consumer of photosynthetic energy and a lot of that energy is spent on defense against pathogens (like fungi and bacteria) entering into this important area of transport.
If the sapwood is injured, the tree has an incredible and diverse defense process. One defense in particular that is easy to conceptualize is when tissues (parenchyma) outside of the vessels (xylem) cauterize the wounded vessels and separate them from sound vessels. In Malus, wounded vessels get plugged with a starchy-watery gum that is aptly named “vessel plug.” Other trees have tyloses instead of gum, and when the vessel (xylem) is injured, the parenchyma tissue grows into the cut chamber to seal it off3 .
I’m telling you about vessel plugs only to hammer home the point that sapwood has a lot of defenses that work tirelessly to keep invaders, whether from an accident or from decomposing heartwood, away from their life-transport network. This is part of the reason why maintaining a youthful vigor in a tree is important, because younger wood contains a higher ratio of sapwood to heartwood, increasing the defense capabilities of a tree on a minimal energy budget.
The higher ratio of sapwood to heartwood is also why it is better to prune younger wood on fruit trees. When pruning, the wound is much more efficiently cauterized and uses less energy.
I’ll also note that the ability to cauterize, or create fast boundaries to some sort of attack, is often genetic. Look no further than fireblight tolerance in a durable apple like the Dula Beauty (triploid) compared to the sickly Esopus Spitzenburg to get a better idea of the genetic range.
Pruning larger limbs. When I consider pruning larger limbs, the rule of thumb for me, unless a giant intervention needs to happen or I’m topworking (grafting in place), is that I often don’t cut limbs larger than 4 inches in diameter. This is strictly something I do in considering the tree’s energy. If the ratio of sapwood to heartwood goes down with age, then it takes a lot more photosynthetic energy (that starch-water mixture) to plug up a larger wound on an apple than it would a smaller wound. Add that energy expense to the tree simultaneously trying to activate dormant buds to create new growth, and even I’m exhausted. Let me be clear, though. I’m not doing this to protect from heart rot, which costs the tree relatively little energy. I’m doing this to help the tree balance its defense and growth energy.
Hollow trees in the orchard: Mycorrhizae If you believe that hollow trees create their own compost and self-fertilize, and if you believe that pruning trees is a way to make hollow trees more stable, then let’s briefly mention mycorrhizae.
Mycorrhizae is the fungal network that is known to connect trees to other trees and allow them to talk and share resources. They connect trees to other resources by having their hyphae (or the fungal threads of mycorrhizae) grow in and around the tree roots. The roots release sugary exudates, which feed the hyphae and give them energy to go mingle. What causes a tree to release sugary root exudates? Pruning is one way, because tree branches are connected to tree roots. Once you start pruning a tree, the fine root system connected to those branches will die back. It’s not a 1:1 prune: root dieback ratio, as the root system is larger than the crown, but there is for sure some dieback.
What’s more interesting to me, however, is the confluence of fine root dieback from pruning, plant-microbe interactions from a hollowed out trunk and fungal hyphae in the soil. It’s a bit like Captain Planet; when these three powers combine, nutrient uptake and overall ecosystem health are enhanced. And this is why I’m on team ‘hollow tree.’ It’s almost as if the tree is creating it’s own “edge,” or diverse environment in which it and everything around it thrives in a wild and chaotic balance.
Final Comments (for now):
Instead of viewing hollows as condos for pathogens, view them as beneficial habitats that improve your orchard ecology. They are important refuges for all sorts of critters, from insects to birds, microbes to fungi, and maybe even a black bear (just kidding). Given how important these hollows are, NEVER! and I repeat, NEVER! Fill those holes up with concrete or bricks or anything else. Not only does it royally piss me off to ruin a chainsaw chain to some branch that was filled with concrete, but it’s not helping the tree in any way. And would you want to come home one day only to find your house filled with concrete? No.
Let’s keep an open mind to heart rot, ok? It’s performing a pretty amazing ecosystem service with no inputs from me.
NO NO NO NO NO NO NO NO NO NO NO NO NO!
1.) Mattheck, C., Bethge, K., & Tesari, I. (2006). Shear effects on failure of hollow trees. Trees, 20(3), 329–333.
2.) Wessolly L, Erb M (1998) Handbuch der Baumstatik und Baumkontrolle, Patzer Verlag
3.) Bonsen, K. J. M., & Bucher, H. P. (1991). WHAT ARBORISTS HAVE TO KNOW ABOUT VESSEL PLUGS. Arboricultural Journal, 15(1), 13–17.
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One of the most important considerations to me when growing apples in the South is if the cultivar has a tolerance to pests and diseases. Called “the final frontier” by my Northern and Western apple growing friends, the Mid-Atlantic and the rest of the US South are notoriously difficult areas to grow domesticated fruit. In true Southern hospitality, our soupy humidity and hot temperatures not only extend a warm embrace to all sorts of pest and disease here, but invite them to stay for a long while and breed.
Despite this high diversity of fungal, bacterial and insect pressure, there are still old apple trees in the landscape that have survived decades upon decades of environmental assault. These trees have been the subject and target of much interest in my network of fruit explorers, as these specimens are proof that it is possible to grow purposeful fruit and trees in this landscape without toxic, self-perpetuating inputs. In past essays, I’ve discussed rootstocks being a factor in this, where larger root systems tended to produce healthier trees. But there are more factors in resilience than just the root system. In today’s essay, which has literally been in my drafts for 3 years, I want to discuss something I’ve been casually studying for years: Polyploidy, or having more than 2 paired sets of chromosomes.
I’ll begin with a bit of history. In the early 1900s, there was a Swedish plant breeder and geneticist named Herman Nilsson-Ehle, who had spent much of his professorial career breeding wheat and oats for high yields in Sweden. He was a huge fan of Gregor Mendel, who had released his findings on inheritance only 8 years prior to Nilsson-Ehle’s birth, and his whole outlook on plant breeding research was a hat tip to Mendel. Mendel, for those of you who may be struggling to remember, was the Monk who stared at pea plants and developed the fundamental laws of inheritance, which we encountered in high school biology as the punnett square .
Before I go any further, I want to give a quick warning. From my research on Nilsson-Ehle, it appears he was a fan of “new Germany,” and saw the genetics research under Hitler’s regime as a means to save the world. In order to only showcase the apple breeding aspect of this man, I’m not going any further in this subject. If you want to read more on his thoughts, which scarily echo modern times, you can go here: Lundell 2016.
In his early research of breeding cereal crops, Nilsson-Ehle would sometimes observe natural mutations in the hundreds of thousands of seeds he planted out for observation. These mutations had much larger, rounder leaves and after poking and prodding these mutants, he discovered their large size was due to having 2 additional sets of chromosomes, or polyploidy (Usually a diploid (2 sets of chromosomes), these plants were now tetraploid (4 sets of chromosomes). These plants exhibited giantism in all ways aside from vigor (which was relatively low). While the leaves and shoots were much thicker than diploids (2 chromosomal pairs), the flowers, fruits and seeds were nearly double in size. This was remarkable to Nilsson-Ehle and prompted him to theorize: If I take this mutant tetraploid and cross it back with its diploid self from the same cultivar, I should get a triploid (3 sets of chromosomes) that brings about enhanced genetics of both!
He was right. The tetraploids he crossed with diploids produced triploids that were more vigorous, hardy and resistant to disease than their diploid or tetraploid counterparts due to enhanced genetic modifiers inherited from the parents of two different ploidy (tetraploid and diploid). This brings me back to fruit exploring in the Mid-Atlantic and Southeastern US. The large majority of US cultivars known today as being able to tolerate fireblight, apple scab, powdery mildew, and loads of other issues while still persisting in the Southern landscape for decades upon decades are triploids! Including the Dula Beauty, my sturdy family apple cultivar.
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So the US picked up on Nilsson-Ehle’s breeding work and adopted it to their work in the states to breed for hardy, disease resistant apples, right? Nope. WW2 happened and we were already distracted with breeding for scab resistance (more about that in a bit). In 1950, famed berry breeder George Darrow reported on Nilsson-Ehle’s work in an address to the American Horticultural Society. In this address, he mentioned the premise behind Nilsson-Ehle’s work and connected the dots in how this way of thinking has translated into berry breeding for larger, higher quality cultivars. He briefly mentioned apples in this address, reporting that a tetraploid sport (mutant) of McIntosh had been found growing on branches of a normal McIntosh tree in New England, but the mutant branch was only half tetraploid, as the cortex of the wood was diploid (making it a ploidy chimera). He said they were trying to stabilize the McIntosh chimera as a full tetraploid through tissue culture, and I believe they achieved this due to the photo below. This was the end of an interest in sustainable fruit breeding in the US, in my grumpy opinion.
Come on, Eliza, what about the Liberty apple? Goldrush? RedFree? Prima? [Slight rant/history on apple scab. Skip to below scabby apple pic to avoid]. Sure, there was a breeding effort between selected US land grant universities (PRI= Purdue, Rutgers, Univ. of Illinois) that began in 1926 to create scab resistant apples. They succeeded in doing so in a basic sort of way, which eventually led to the downfall of this research. The style of their research was “monogenic,” or relying on a single gene to control scab resistance in an apple cultivar. There was also a whole lotta inbreeding going on.
The gene identified to have scab resistance is called the “vF gene,” which comes from the cultivar “Malus floribunda 821.” The reason why they picked this gene is because they could identify it in seedlings using molecular markers, so they didn’t have to waste time growing the trees to find out if it was scab susceptible or not. That worked out well enough for a while and they selected some ho-hum cultivars (minus Goldrush, which is awesome but incredibly prone to cedar apple rust) to make available to the public. In 2002, the first reports of scab infection were reported on the scab-resistant apple cultivar ‘Prima.’
In 2011, a German pomologist wrote an article about all of this and, thankfully, it was translated into English shortly thereafter. What he found, looking into the lineage of most US and Euro scab resistant apple cultivars, was a huge amount of inbreeding going on. Not only that, but the cultivars being crossed back to themselves were highly susceptible to scab! I’ll quote directly from the article:
“Today the global fruit breeding industry is producing a wide range of varieties, with one big difference: the overwhelming majority are descendants of just six apple cultivars.
The author’s analysis of five hundred commercial varieties developed since 1920, mainly Central European and American types, shows that most are descended from Golden Delicious, Cox’s Orange Pippin, Jonathan, McIntosh, Red Delicious or James Grieve. This means they have at least one of these apples in their family tree, as a parent, grandparent or great-grandparent…”
Many of the PRI releases have these 6 cultivars crossed multiple times in their lineage. If you do this right and bring out the right traits without problems, it’s called ‘line breeding’. If you end up with problems, it’s called ‘inbreeding’.
The second and main problem with this breeding work, in my opinion, was in our complacency with our selections. We basically ignored any further breeding efforts for scab resistance in order to pursue “Crisp” apples. Takeaway message: FEEL GUILTY ABOUT EATING A HONEYCRISP, COSMICCRISP, CRIMSONCRISP KARDASHIANCRISP ETC. BECAUSE THATS WHAT BREEDING LOOKS LIKE NOW INSTEAD OF BEING ABLE TO GROW APPLES WITHOUT MAJOR INPUTS! Too bad we haven’t been thinking about triploids or even multiple-gene scab control for the last 50 years.
Guess who has? Russia.
Since the early 80s, the All Russian Research Institute of Fruit Crop Breeding (VNIISPK) has continued with the scab resistant vF breeding work that spread across the US and Europe, only it is way more badass. Not only are they breeding for scab resistance, but they’re breeding for tolerance to late frosts, consistent yields without having to thin fruit, COLUMNAR growing habit AND Nilsson-Ehle’s version of triploidy (Speak a little more into my dirty ear, Russia). However, the near-sensationalism of these claims doesn’t stop there. Dr. Evgeny Sedov, the primary researcher in this endeavor (and someone I would really love to interview), closes the abstract of one of his scientific papers that goes into his triploidy research with the following that is so, so Russian:
“It is noted that triploid apple cultivars developed at VNIISPK are inferior to none of the foreign cultivars, based on a complex of commercial traits, and they significantly excel foreign cultivars in adaptability. Our apple cultivars may contribute to the import substitution of fruit production in Russia.”
Some mentioned and additional benefits of triploids (Or reasons to pursue more polyploidy breeding):
Adaptability to climate, disease, stress: In the above quote, Sedov writes how his triploid apple cultivars significantly kick other apple cultivar ass in terms of adaptability. And based on my research covering the last 100 years, he’s not wrong. There have been many observations by the scientific and lay community reporting that triploids end up being more cold hardy, more heat tolerant (the thickness of leaves and fewer, larger stomata give rise to a lower transpiration rate and more water retention that can be used during drought), have better nutrient uptake, and improved resistance to insects and pathogens. The theory for triploids having a higher environmental adaptability has to do with an increased production of secondary metabolites, which enhance plant resistance and tolerance mechanisms (as well as chemical defense).
Thinning: Triploids often have low fertility due to a reproductive barrier of having an extra set of chromosomes- making pollination difficult. Some apple pollen tends to pair decently well with triploid apples to get a decent crop. With most cultivars it isn’t great- just good. This could be seen as a boon to this class of ploidy, but I see it as a good thing. One of the greatest challenges to organic apple production is the thinning process. Most non-organic orchards thin using chemical sprays to knock off flowers or fruits. To this day, many organic spray chemicals either do a lackluster job, or oh-god-that’s-far-too-many-job of thinning the fruitlets off, leaving many orchardists to either thin by hand or accept biennalism (which was a 3 hour conversation at Stump Sprouts one year). If you have healthy pollinator populations, less fruit on the tree will guarantee you a return crop the next year, barring other environmental catastrophes (which you’re better prepared for with triploids, anyways).
Vigor: In the past, I’ve written about vigor on the Elizapples.com blog and how it’s my number one enemy in the Mid-Atlantic given my heavy soils, warm temperatures and ample water supply. Though I need to revisit those essays and condense them into my current evolution of thought, the reason for my past concerns around vigor is that I have conditions that induce [what I’d like to think is] “artificial vigor.” In my climate, this shows up as extreme vegetative growth, which sometimes gives rise to heightened fireblight pressure and other vulnerabilities. Though “artificial vigor” is likely what an incompatibility of growing conditions looks like, I’ve started to differentiate it from what I’m calling “true vigor,” or youthfulness through heterosis/hybrid vigor. This is where triploids shine.
When you start digging in old texts, back before the rise of clonal rootstocks, you might encounter mention of two classes of trees referred to as “Standards” and “Fillers.” The “standards,” often mentioned as Baldwin and Rhode Island Greening (both triploids) were larger trees that took longer to bear fruit. These were thought to be permanent trees, or trees that would be around for generations. The “fillers,” such as Yellow Transparent and Wealthy, produce much smaller trees in the same length of time and were far more precocious in bearing fruit. These trees were thought to be temporary, and were planted in between the “standards” to increase production in the early life of the orchard. An unfortunate modern day “filler” would be HoneyCrisp (diploid). Growing in my climate, it is better termed runtycrisp. Super low vigor, gets loads of diseases, precocious bearer, dies early. Sort of an orchard mercenary. This, to me, is a good way to think about vigor. If you’re growing for the long-term, you’ll want a truly vigorous cultivar that teems with youthful energy, and I believe that youth is heightened as a triploid. If you are growing in areas that are full of pest and disease, it is also not a bad idea to have an extra set of chromosomes to help with defense and stress. Relic trees standing tall in the South tend to be triploid and their presence speaks to their youth and defense: Arkansas black. Fallawater. King David. Leathercoat. Roxbury Russet. Stayman Winesap.
With all of this said, we have a lot of work ahead of us to start thinking about what our breeding programs would look like if we set our targets on low-input, no spray, multi-gene disease tolerance and more. I get it, HoneyCrisp can store for a calendar year in my crisper drawer, but that’s all it has going for it after a year in there.
I am pulling for the expansion of ‘process’ industries such as hard cider, vinegar, juices, syrups, etc to become the targets of agroforestry planning and planting enterprises in the near future. Annual or livestock farmers don’t want to mess with sprays or inputs that are outside of their normal non-tree crops care. If they are going to receive incentives to plant trees on their farms, they will want the ones that need little care and have an economic outlet. This will require a new set of apple cultivars to choose from and they have to come from somewhere…
Here is an incomplete list of confirmed triploid apples. Many of these are from the UK and do so-so in my climate. The ones with asterisks are what I have seen as old relic trees in the Mid-Atlantic: Arkansas Black* Ashmeads Kernel* Baldwin* Belle De Boskoop Blenheim Orange Bramley’s Seedling Buckingham* Bulmers Norman Canadian Reinette Catshead Close Crimson Bramley Crimson King Crispin Dula Beauty* Fallawater* Fall Pippin* Frösåker Genete Moyle Golden Reinette von Blenheim Gravenstein* Hausmuetterchen Hurlbut Husmodersäpple Jonagold King David* King of Tompkins County Lady Finger Leathercoat* Margille Morgan Sweet* Mutsu Orleans Reinette Paragon* Red Bietigheimer (Roter Stettiner) Rhode Island Greening* Ribston Pippin* (struggles with brown rot) Roter Eiserapfel (Has 47 chromosomes rather than 51) Rossvik Roxbury Russett* Shoëner Von Boskoop Spigold Stäfner Rosenapfel( Has 48 chromosomes) Stark Stayman* Stayman Winesap* Summer Rambo* Suntan Tom Putt Transcendent Crab Transparente Blanche Vilberie Vixin Crab White Astrachan* Winterzitronenapfel Winter Pearmain Washington Strawberry
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Every year, around this time, social media begins to rumble in uproar over Bradford Pear (Pyrus calleryana). With headlines like “The Curse of the Bradford Pear,” “Bradford pear tree: How the trees can hurt people, then environment,” and finally “I Just Hate Bradford Pear,” it’s no wonder people have it out for them. The trees have NO GOOD PRESS and, unfortunately, it’s much easier for hoards of people to fall in line with anti-invasive rhetoric than to understand who or what they are trying to demonize. In light of this, the time has come to take a stand for this poorly misunderstood tree.
Bradford pear belongs to the species Pyrus calleryana, which is why it is sometimes called “Callery.” This species of pear is native to China, where the range goes from sea-level to 5000 feet in elevation, spanning a thousand miles inland as the crow flies. Cousins of callery pear are also in Northern Korea and Japan, showing an immense climate and site adaptability for the species.
How did it get to the US?:
In the early 20th century, the Pacific Northwest contained many orchards of Pyrus communis, or French pears. These pears were being ravaged by fireblight (Erwinia amylovora), a native bacterial disease, and professor Frank Reimer was pulling his hair out over the potential loss of the West Coast commercial pear industry if a control for fireblight wasn’t found soon. Researchers have long known that Asia’s gene pool for fruit and nuts is much older than European or American genetics, and likely hold resistances or much improved tolerances to pest and disease due to the long and slow co-evolution over time. Reimer knew, from his research, that Pyrus calleryana and Pyrus ussuriensis were inherently resistant, so he put out an SOS to obtain pear seed from Asian regions in order to hopefully find resistance.
Harvard’s Arnold Arboretum in Massachusetts answered his call in 1908, sending plant explorer EH Wilson (aka “Chinese” Wilson) to China to see what he could find. Once there, he collected P. calleryana seeds from 4,000-5,000 feet in elevation and sent them to be grown out in Boston. Many of these proved to be hardy for Massachusetts and many people, including professor Frank Reimer, got excited. Given the potential for Pyrus callerana to save the commercial pear industry in the PNW, the USDA decided to add callery pear to their fruit’s explorer’s collection list.
At the time, the USDA had been going through a period of glitz and glam concerning their plant exploration program. The golden child at the center of this hubub was the darling plant explorer David Fairchild, the person responsible for bringing over German hops, the avocado, and kale (among many, many other things). With his notoriety and prestige, he married into the fabulously wealthy family of Alexander Graham Bell, and was feeling the need to step down from his travels abroad in order to start a family. Instead of Fairchild himself going on the pear mission, he delegated the job to one of the toughest mofos alive: Frank Meyer. Dutch born, Meyer was known for his ability to walk 30+ miles a day, everyday, forever.
This would be no small job, either. According to Arnold Arboretum, 25 pounds of seed would require picking seeds out of 5000 pounds of fruit. That’s the equivalent of 125 bushels of tiny (8.5mm on average) callery pear fruits, which would be maddening to collect by hand. This wasn’t a problem for Meyer, though, as he probably preferred tiny pear seeds to interacting with people. With his marching orders, he set out on this pear mission, writing the following to his boss, David Fairchild:
Once the first batches of seeds were back in the States, they went under commercial pear rootstock monitoring for fireblight resistance. These pear seeds produced vigorous, uniform trees that, when inoculated with fireblight, proved to be the most resistant of any pear tree they had evaluated, by a landslide (double the resistance of Pyrus ussurriensis and far more vigorous). The chart below reveals the results of this trial:
In later studies, Reimer reported that 11% of P. calleryana trunk inoculations showed a severe fireblight infection. Which, by the way, is pretty amazing. When I innoculated my apple seedlings with fireblight ooze, 95% of them showed severe infection or died.
In addition to having stellar fireblight resistance, Callery pears were tested on a variety of sites and were found to thrive in nearly all soil and moisture scenarios, from coarse sand underlain by granite to heavy clay. They also found Callery pears to have a lower chilling requirement than P. communis (French pear rootstock) (source), allowing for it to be grown in more erratic seasonal conditions (which might not have been a big deal then but MAN is that a big deal now). This pear species was seen as the most bomb-proof, resilient rootstock around on which to grow our favorite eating pears, and even produced yields 32% above the same cultivars grafted to P. communis (Source: Westwood, Pear Rootstocks for the Northwest. NAFEX POMONA Vol 3, Number 2, 1970). With the excitement and growing popularity of using callery pear as rootstock, the US continued with seed gathering trips to China for decades.
From Amazing to Pariah, what happened?
First of all, most of what you read about the introduction of Bradford pear (P. calleryana) to America is incorrect, as I’ve just given you the real history above. Outlets like The Grumpy Gardner, a now-retired columnist for all things horticulture at Southern Living Magazine, have done a lot of damage spewing emotion-based information to people who don’t know any better. With little challenge to any of the points ever made, he and others managed to create a culture of emotional reaction surrounding P. calleryana, rather than a much needed practical one. For the record, the chances of you being allergic to Bradford Pears are slim to none because they aren’t wind pollinated. Bullied, bruised, blamed and constantly soaked in toxic agri-chemicals to try and kill it, the Callery pear is one of the most shamed species in the US. If you don’t believe me, look no further than the hundreds of online articles that alone focus on how the blooms smells like male ejaculate (that’s spermadine and putresine you’re smelling and it’s in a lot more plants than you think, including the beloved American chestnut).
Why didn’t Callery become the main rootstock of all pear production in the US? According to Reimer, on average, the tree isn’t very hardy (doesn’t like to grow colder than 7a, or below -10 fahrenheit), it doesn’t propagate all that well from stooling beds (primary means of producing rootstocks in the nursery industry), and has poor fruit qualilty. Why fruit quality matters for a rootstock is beyond me, but it was listed as a reason. In regions 7a and hotter, though, Callery pear is the best rootstock onto which one could graft European and Asian pear cultivars, but the research conducted on these pears was West coast centric and never really made it over to the East, even after Callery became a dreaded invasive.
Root Stock to Ornamental to Monster:
The Glenn Dale Maryland USDA research site had planted many P. calleryana seeds from Frank Meyer’s collection and by 1950, there were still a few P. calleryana trees remaining at the location. In 1952, researchers took notice of one particular thornless (many wild apples and pears have thorns) tree with an amazing white bloom (Callery produces fruit on lateral branches, on the previous year’s wood and on spurs of older wood. According to Reimer, It probably produces more blossoms than any other species of Pyrus). Thinking this could be of ornamental quality, cuttings were taken from this tree, grafted onto a seedling Callery pear rootstock, and planted in a subdivision nearby for testing. These trees were pruned/maintained, and after 8 years of oohs and ahhhs, they named the cultivar ‘Bradford,’ in honor of the horticulturalist who recognized its potential as an ornamental tree. By 1962, the Bradford Pear was available commercially and it became one of the most widely planted suburban trees in the US.
Around this time, other research stations and arboretums were noticing the ornamental value of the seeds planted from Meyer’s explorations. The National Arboretum produced, from a seedling selection, a cultivar called “White House,” and a seedling now known as “Autumn Blaze” was selected from the Horticultural Farm in Corvalis, Oregon.
The late 1960’s welcomed a gold-rush era of Callery pears, with many nurseries planting out seedlings from the original collections of Frank Meyer in order to find the next Bradford. This, friends, is where we start to transition from Amazing Rootstock to Amazing Ornamental Street Tree to “The Curse of the Bradford Pear.”
Pyrus calleryana is amazing for all of the reasons I listed above (insect and disease resistance, able to grow in a variety of soils and climates), but did you know it is also largely resistant to pest like deer, Japanese beetles, and wood boring beetles? The tree is precocious (often 3 years to fruit), the first to leaf out in the spring and the last to drop its leaves in the fall/winter. All of these qualities are noteworthy, yet have gone largely unnoticed due to one thing: The original ‘Bradford’ tree was self sterile.
When a tree is self-sterile, it cannot reproduce with itself in order to create progeny (fruit with viable seed). This wasn’t a problem when Bradford clones were planted out in the DC suburbs, because they were all genetically identical. When the bees would visit the flowers of one tree, and then the next, the pollen was sterile and did nothing to further fruit development. However, that was just one cultivar’s genes.
Remember when I said that Meyer walked 30+ miles a day? He covered so much ground while in China that he sent seed from Callery pear populations hundreds of miles apart. As it turns out, these populations produce genetically distinct cultivars under the species, and are totally able to cross with one another. Which they did once all those populations were brought together to intermingle in the US.
When the other ornamental selections like “White House” and “Autumn Blaze” showed up on the streets, the self-sterile Bradford pears soon became promiscuous in the neighborhood. By 1980, 300,000 Callery pear trees had been planted as street trees, producing huge amounts of small fruit with viable seed. From there, seedlings spread far and wide via birds and raccoons.
Today, in certain areas of the US, Callery pear seedlings can be found inhabiting fence-lines and ecologically stressed out pastures/roadsides, causing everyone to scream INVASIVE! THEY’RE INVASIVE! OMG KILL THEM. I CAN’T EVEN THINK STRAIGHT RIGHT NOW. EWWWW. IS THAT SPERM I SMELL? KILL.
But let’s take it out of all caps for a moment and go a bit deeper, because they deserve a chance.
Why is it so successful in the landscape?
Look, when you get into research about exotic plant species in the US, a huge majority of papers are biased in their research scope to focus on their invasiveness rather than what they offer. For instance, this paper (and there are many like this) decided to go ahead and only name one bird, the invasive European Starling, as being responsible for spreading callery pear in the landscape.
This is a type of fear mongering that I find over and over again. Rather than list the native birds that actually feed on Callery pear (there are MANY), research tends to dwell on the negative ones in order to further demonize this tree. I’ve been writing this paper for nearly 3 years (because 2 editions of this have been deleted on accident) and the only research I have been able to find listing native birds comes out of non-profit research and a masters thesis from Michigan, both BURIED in google. Over time and with much frustration given the extreme biases of US research, I decided to broaden my search for Callery pear dispersal in other countries, and the following is what I found out of Australia:
As you can see from the diagram above, the size of fruit directly corresponds with the number of frugivorous bird species that eat them. Like most ornamental fruit trees, Callery pear’s small fruit (8.5mm on average) is relished by birds, especially since they often have a tendency to hang on the tree well into winter- providing some much needed winter food for the birds that stick around.
Ok, so lets briefly put this all together: Ornamental= small fruit= bird food= birds poop= up comes Callery pear= produces thorns so not browsed= very tolerant of all the diseases= very tolerant of any soil type= it grows and thrives. But also, the Southeast is seriously just like China’s native range for Callery Pear (dark grey)…
I have two trains of thought that I’d like to go down: Fruit size and human impact on the land
1.) Fruit size: The average untamed fenceline in my climate contains autumn olive, barberry, multiflora rose, Callery pear, oriental bittersweet, honeysuckle, greenbriar, flowering dogwood, privet, american holly, hackberry, black cherry and a growing number of ailanthus. With exception to Ailanthus (which has a winged seed), what do all of these species have in common? They all produce fruits less than 15mm in size. Whenever there is a perch, such as a fenceline or a powerline, you’ll often see these species because they have small fruits that birds eat. The reason why we see so many Callery pear along these areas as well as in old fields and the built environment leads me towards the second thought…
2.) Human impact on land. Unlike many of the other species I mentioned in the paragraph above, Callery pear can thrive in compacted, low nutrient, poor draining soil with blazing sun and oppressive humidity. The reason why we see so much of it is because it thrives where humans have arrived and destroyed. Places like old fields, for example, which are are nutrient poor and compacted due to the robber-farmer that took more than the field could supply. Often in my area, those fields once supported tobacco and now are hayed by good-ole boy farmers in the area to keep the property in ag taxation for the owner, but no one ever puts any love/nutrition back into the land. What will grow in this scenario? Callery.
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How can we make these pears less invasive?
Due to Callery’s fruit size attracting a high diversity of fruit eating birds, we can’t stop birds from eating the little pears and pooping in marginalized areas like fencelines and worn out pastures. To think we can kill enough Callery pear to make a difference is a lesson in futility because 1.) We live in the United States and you can’t go kill a neighbor’s tree in the name of INVASIVES if they don’t want you to and 2.) Each tree produces thousands of fruits. So, with that said, here are my top solutions to sustainably make Callery pear less invasive and more useful.
1.) Citizen Breeding. What makes Callery pear invasive is its ability to produce copious amounts of small fruits, which birds then eat and distribute all over the place. It seems logical, then, to want to try and breed larger fruits into our populations of Callery in order to stop the spread by birds. In order to reduce invasiveness by around 80%, all it takes is getting these trees to produce fruits that are around an inch (25mm) in diameter. Throughout the South and Southern New England, this is happening already in the “wild.” I’ve noticed trees that strongly look to be be hybrids of P. calleryana with P. communis (French) and/or P. pyrifolia (Asian). These trees have much larger fruits, usually golfball sized or larger and are often loaded with fruits dripping from the trees due to callery’s lateral bearing genetics (a possible phenotype identifier for callery hybrids). No research that I can find has evaluated the genetics of these larger fruited callery-like pears to see what exactly they are hybridized with, but I’m happy to help supply specimens if anyone out there takes an interest.
What is needed to hybridize these pears and get them larger? For starters, you’re going to need a collection of pears that bloom at the same time as Callery, which is quite early. Russian/Cold Climate and early Asian pears are likely your best bet for this, so I went through the GRIN database and have made a starter-list (there are a bunch more):
PI 541904- Seuri Li PI 45845- Yaguang Li PI 437051- Jubilee (cold hardy) PI 541925- Kor 2 PI 267863- Pingo Li PI 134606- Tioma (cold hardy) PI 278727- La Providence PI 278731- Sivaganga Estate PI 307497- Seu Ri PI 292377- Ranniaia Mleevskaia (cold hardy) PI 541760- Chieh li x Japanese Golden Russet PI 278729- Samy’s Estate PI 541761- Chieh Li x Japanese Golden Russet 2 PI 541905- Szumi PI 127715- Krylov (cold hardy) PI 541326- Angelica Di Saonara PI 324028- B-52 (cold hardy) PI 541290- Mag 1 (cold hardy) PI 132103- Shu Li PI 312509- Tse Li
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You can request scions online from September 1 to February 1, of every year from GRIN. You can also probably buy many of these cultivars online. From there, I highly recommend you share scions of these for free every winter, as I plan to do, in order to help infuse larger fruiting genetics into Calleryana.
You might notice there are a bunch of Asian pears in that list and you might think: Eliza, those pears are super fireblight susceptible! And you are right, of course, but think of it this way: MANY trees that are listed as fireblight susceptible are actually quite tolerant to FB once they are established and reaching sexual maturity. With Callery being an amazingly fireblight tolerant rootstock, this should help to get your topworked trees past the first 2 years of heightened susceptibility so they can start to fruit. Once these Asian pears intermingle with Callery, there are two possible outcomes:
1.) The hybrid offspring are more fireblight tolerant than the grafted Asian pearent’s tolerance
2.) The hybrid offspring is less tolerant to fireblight than the grafted Asian parent’s tolerance and will probably succumb to the disease and die on its own.
Either are a win-win, really.
Next, you’re gonna need to go into your pear thicket and do some cutting and grafting. There are two scenarios I see often:
1.) Field full of Callery: If you have a thick field of calleryana, I would recommend getting a forestry mulcher in and cut/mulch rows into the existing Callery stand. Then, run the mulcher to cut out trees within the rows left standing so the remaining are at 15 foot spacings. Top the trees you’ve left behind above deer browse ( throw into the alley and run over those, too, with the mulcher) and graft on the early blooming large fruited cultivars.
2.) Fenceline/Border with Callery: This is the scenario We’ve been dealing with over the past few years along the farm fenceline. First thing I do is flag the trees I want to keep, which are at 15 foot spacings along the fence. Then we cut out and chip all the non-flagged callery trees using my neighbor’s chipper (I mulch my orchard with callery pear wood chips). While we are cutting out the non-flagged trees, I go ahead and also cut the tops out of the flagged trees. I pick a height that is above deer browse height and also has a lot of clear wood without branches, because that helps with grafting. In April (I’m in zone 7a), I make fresh cuts on the remaining pear trees and topwork all of them to fruiting cultivars. We’ve been doing this for 3 years and 2018’s topworked pears will be producing fruit this year.
This is totally doable and the result? An orchard of pears! You’d have to cut the tree down anyway if you were going to spray it, so why not turn it into a producing pear tree of value? My neighbors even pitched in to help us cut and chip in the name of supporting my vision and also getting rid of the fruiting portion of the Callery trees.
In 2-3 years, your top-worked pears will be flowering and that’s all part of your plan, as bees will mingle between surrounding Callery and the large-fruited cultivars you grafted. All of a sudden, your chances of getting larger fruit to come up from that fertilized seed will exponentially increase. And did I mention that you’ve also made yourself an orchard?
2.) Use them as rootstocks! Every Callery pear growing is automatically the best pear rootstock around. For all of you people out there who are inundated with deer pressure, graft to the Callery pears to any pear you’d like (or Winter Banana apple). Sure, you’ll get lots of leafy re-growth off the trunk for a couple years (which the deer or other livestock eat as tender shoots), but its also really easy to remove new growth with your hands (they pop off) or slightly older growth with pruners, and brand new shoots don’t have thorns. You’ll start to get fruit in 2-3 years.
One of the main reasons why Callery didn’t catch on as a rootstock, aside from root propagation failures and hardiness, is that they don’t produce dessert fruit (fruit meant for out of hand eating). This is the same reason why we’ve lost SO MANY fruit cultivars in the last 100 years. If you weren’t a dessert cultivar chosen by the cooperative extension to be grown in the early 20th century, you were phased out. However, in today’s markets, large fruited Callery pear hybrids really have a chance in fermentation, specifically cider blends and perry (cider made from pears). They are high in sugar (over 16% brix on average for the 200 or so hybridized trees I’ve evaluated), and run the gamut in acidity, tannins, aromatics and unusual characteristics. Since these trees are so disease and pest tolerant, which allows them to grow and produce copious amounts of fruit without the hand of humans or chemicals, they stand to produce the most sustainable fruits and alcohol in the South. We need more people working with them in order to make this happen because they aren’t apples and they need their own methods.
Last year I went through a collapse. The best I can describe it is the imagery of me walking down a dirt road while being shot with arrows. I tried to pull them out and fight back with the first few shots, but more shots continued to hit and sink into my flesh. By late fall, the fight was gone in me. I was bleeding out and in a dark place. I had no choice but to let the darkness envelop me.
During this period of time, I questioned myself, my life, my passions. I felt hollow. What was it all for? If I am to pursue my passions, will I always suffer like this? And how much more can I handle before it’s no longer worth it? As these questions floated by me in the darkness, I heard a voice whisper: “Eliza, you are here to love apples.”
It wasn’t the first time and I have a feeling it won’t be the last time that apples pull me out of depression. Slowly and incrementally, I started to give myself time to think about the things I loved and the patterns of my life. With each passing day of thinking about what I loved, business plans emerged. Caution and negative feelings turned into strategy. Conducting a personal inventory on what I had in my possession turned into talks, workshops, and mulberry trees for sale. When put all together, HogTree emerged.
First of all, what is HogTree?
HogTree is a diversified orchard system designed and synched to the rotation and feeding of livestock while also growing commercial process fruit. Imagine a paddock filled with trees that drop fruit/nuts at the same time. Now imagine many paddocks incrementally dropping fruit from May through November. That is HogTree.
I have mulberry cultivars that will drop fruit from May through July. I have around 30 apple cultivars that, when put in order, will drop fruit from late June through November. I have special genetics gathered from notable Quaker horticulturalists like J. Russell Smith, John Hershey and Yardley Taylor to add to this system as well, including: persimmons, chinquapins, chestnuts, pears, pecans, oaks and hickories. In essence, HogTree is a practical arboretum designed to preserve rare or otherwise unwanted cultivars in order to feed livestock…and more.
Summer drop scheme for apples in my area.
Why would you design an orchard to feed livestock? Because that’s the first income layer. If you are going to start an orchard, you’ll need to make some income during the time it takes for the orchard to start bearing (This is also important when trying to get a loan from the bank). Some people grow annual vegetables and I think that’s perfectly fine, however I do not want to spend all of my time bending over. I’m a much happier person if I reach up rather than down. I also want to incorporate an income stream which will help manage the orchard throughout its lifetime. After a few years of having pigs in orchards, I’ve discovered that pigs do the job of an unskilled intern and deposit fertility in the process.
What about the second layer? That’s commercial process fruit production. Interspersed within these paddocks in inventive ways are cultivars which grow well for me in this area and have a high quality in value-added markets. These fruits will be mostly managed by livestock with a few steps of intervention coming from humans. Though it’s 5-6 years out, I’ve already promised this fruit to amazing makers/friends/business people who will not only treasure this fruit and turn it into the best product they can, but who also give a shit about our impacts on this earth and humanity. My fruit will go towards producing products with a positive and aware message.
Before I go to the next layer, I also need to put out a disclaimer. When I first got into apples, I wanted to grow alllll the varieties. I wanted to find uses for them all, so people could feel as rich as I felt when having access to hundreds of varieties/tastes/textures/uses. I started growing heirloom apples for cider because they otherwise had no market due to natural cosmetic blemishes/weirdness, but were too special and delicious to me to not be given a purpose. In growing them for livestock first, process second, I’m giving them a new niche.
Is there a third layer? Yes, the nursery layer. This year I’m selling the Hicks Everbearing Mulberry along with what we think is Stubbs Everbearing Mulberry (positive ID coming next month (May)) through HogTree. Both were championed by J. Russell Smith and John Hershey for being the original “Hog Trees,” with each tree responsible for feeding pigs and chickens for 3+ months in the South. I sold 250 newly grafted trees in January, which are shipping out now, but this coming winter I will be selling hundreds more as 4-5 foot tall trees. In the next few years, I’ll start to sell the apples, chestnuts, chinquapins and persimmons that are part of my drop scheme. HogTree is an orchard system. In selling these trees, I’m selling the order in which they belong in the scheme.
Fourth Layer? Of course!: Talks. Workshops. Tours. Helping people to learn from my mistakes. U-Pick (If you have a system designed to efficiently rotate livestock through, humans are no different).
There are more layers, but this is the 5 year layout as of right now. Now to reality!
What do I have right now? I have an 8 month lease on 10 acres in Loudoun County, Northern Virginia. The 8 month lease is so I can prep the ground for orchards to go in this winter with pigs (an annual income), while also keeping a healthy dose of caution related to land tenure. In 8 months, the landlord and I should be able to see if it’s a good fit and will then discuss a long-term lease. I’ve been burned badly in regards to land tenure and much like being in a romantic relationship, I do not feel comfortable planting trees which will be around for my lifetime after the first couple dates between me and the landlord. Working with pigs as my first activity on this new property feels safe, whole and doable.
10 pigs will be arriving in early May from David Crafton, of 6 Oaks Farm. He is a passionate wealth of information and all of his pigs are from pasture genetics, so they contain the necessary gut biome to raise them in an orchard-in-the-making setting. He has been working for years to develop his own breed, the Carolina Forest Spot Hog, but in waiting for this breed I’m receiving a heritage-breed mix from him largely consisting of a large black x tamworth cross and bluebutt crosses. The goal is 200+ pounds of delicious marbled red meat in 7 months with them eating 90% pasture/fodder. I’m excited to work with them.
With that said, this timeline is how I currently predict HogTree will be developed in the next few years:
Year 1: The land is responsibly “pigged,” removing grubs, spreading minerals/nutrients and planting cover crops after them in order to prep the ground for orchard plantings. This is also a trial run for a long-term lease with the landowner. These pigs will be supplemented with some off-farm feed (non gmo peas, barley and whey mostly) because they are working to transition a blank canvas/pasture into an orchard and will need some supplement to grow within my 7 month time frame. HogTree the nursery sells mulberry trees online.
Year 2: (If pig year 1 pans out, otherwise repeat yr 1 on new piece of property), I will be planting fodder trees and fruit tree rootstock. Considering fodder trees, I have the genetics for trees whose leaves are as nutritious as alfalfa and way more drought tolerant, providing high digestibility/minerality and nutrition when the grass starts to underperform. These trees will be harvested annually starting in year 3. HogTree continues to sell mulberries online.
Year 3: The fruit tree rootstocks will be topworked (grafted). In addition to pasture, the pigs will be eating tree fodder and early season mulberry fruit by this point. HogTree sells summer apples and mulberry trees online.
Year 4: Pigs will hopefully start to taste their first apples off some trees. They will continue to eat pasture and leaf fodder from the trees. The full gamut of fruit trees will be available through HogTree.
Year 5+: Pigs will be fed/fattened/finished off tree leaves, fruit, nuts and pasture. Harvests for process fruits will begin.
*In order to make this vision and business plan work, I will need the investment of consumers. That means I am opening up a waiting list for 20lb box/quarter/half/whole hogs for the 2018 year. Please realize that in buying this pork, you are supporting the future of HogTree’s orchard system, which will show the important links between animals and orchards. Please consider buying pork from me if you want to see HogTree set this orchard system into motion. Click here to get on the waiting list!*
Update: Support my writings and more through the purchase of charcuterie at www.hogtree.com
Earlier this year, as I was doing some research on the effects of grafting apple varieties to Malus angustifolia (southern crabapple), I kept running across interesting accounts of noticeable changes to the apple varieties when grafted to crabapples. One of these changes is in flavor, which is what I’m writing about today.
This is the original snippet that sparked my interest. Why? Because this dude back in the 1800s is telling me that when he took the Bethlehemite apple, a dessert/culinary apple from Ohio, and grafted it to a crabapple rootstock, he got something different from the original variety. The grafted Bethlehemite apple had developed some astringency. Astringency is the key word here.
OMG, DID THIS GUY TURN A DESSERT APPLE INTO A CIDER APPLE BY GRAFTING IT ONTO A CRAB ROOTSTOCK?
This thought has rumbled around in my head for the better part of this year and whenever I had a moment to sit at the computer and not read my emails, I researched this topic a bit more. First, I went back in history (via google books) to find more testimonials of these findings. Here are a few:
I could go on, but there are many, many testimonials in favor of rootstock having a flavorful impact on the grafted variety. There were some naysayers, who basically just said “this can’t be so” and changed the subject. But all in all, my historical research has been in favor of a rootstock’s ability to change flavor in apple varieties.
Eager to pursue this topic, I started looking up scientific papers on the subject and started with this, Cornell’s research on nutrient uptake by different rootstocks. The thoughts and questions of the horticulturalists back in the 1800s seem to still align with the questions of today, as seen in this conclusion:
“The ability to match the nutritional requirements of a scion cultivar to a specially tuned rootstock…” COULD, in my opinion, create a cider apple out of a friggin’ dessert fruit.
Positive, I kept up the research and found considerable evidence in citrus fruit that rootstocks can change the flavor of the fruit. Here. Here.And Here.
This study, which looked at an apple rootstock’s impact on triterpene (cancer and immune disease prevention chemical compounds) found this:
“The largest differences in triterpene content were found between rootstocks. The results showed that both at harvest time, and after cold storage except the first harvest time samples, the apples from rootstock MM106 had significantly higher triterpene content compared with those from M9; … Selecting suitable rootstock might increase the triterpene content in apple peel in practice production.”
And this study on different rootstock’s impact on peaches showed that the variety ‘Suncrest’ on Julior (rootstock) and GF677 (rootstock), followed by Ishtara (rootstock), produced fruit with the greatest antioxidant activities and total phenolic contents. The ‘Suncrest’ on Citation (rootstock) and, especially, Barrier1 (rootstock) had reduced nutritional values of the fruit.
WHAT DOES THIS ALL MEAN?
Right now, everyone I know who is planting a cider orchard is planting on known rootstocks like the MM series or the Geneva $eries. With these rootstocks, we know what size of tree we’ll get and we generally know when it will start cropping apples. This is valuable information because we want order and sense in our orchards. We also know the disease tolerances of each rootstock, which have been known to convey some resistance to the apple scion, and that’s all well and good. There are many knowns of these rootstocks because they’ve been extensively studied…for dessert fruit. But what about cider fruit? How many rootstocks have been thrown out in university trials for imparting astringency to an apple? Probably a lot. But what if this is what we’re after?!
If someone came to my farm peddling their wares and told me that they could take my dessert apple and turn it into a cider apple with one of their amazing magical rootstocks, I would buy it. I’m sure it would be a hit. This is why we have started in on the private research of grafting apple varieties to different rootstocks for the purpose of flavor/nutrient evaluation (as well as growth influences, which is another blog entry).
Currently, my partner and I have Malus angustifolia (southern crab), Malus baccata (Siberian crab), own-root, M7 and M111 trees grafted in our nursery to the same variety. These will soon get planted out at the farm in an area set up for evaluation. This, I believe, is another untouched frontier whose findings could be incredible for the future of growing superfruits, having value-added rootstocks, and growing with lower inputs.
So far, the science and the observations are there. There’s much more to learn, but why not start in on the fun?
I remember my first encounter with the “serious physiological disorder” called watercore. I was at an heirloom apple event in New Zealand, staring at a table full of old British varieties trying to decide which one to buy and eat first. I settled on a little russeted apple called Pitmaston Pineapple and once in hand, I took a large bite out of it. The inside, to my surprise, looked like this:
The taste was very sweet. A different kind of sweet, though, and it took me a year to come back around to figuring it out. This variety of apple, along with many other varieties, is susceptible to a “disorder” called watercore.
To the dessert grower, this “disorder” is bad news. Most people don’t want to bite into an apple which appears to have a water-soaked flesh because we’ve been taught that anything other than the usual white-crisp-juicy is to be avoided. However! I’m here to tell a different story, potentially one for the watery underdogs. A hopeful cider apple story.
First, let me give you some background on watercore…
To the apple industry, watercore is considered a “nonparasitic disease,” where the apple appears to have a water-soaked flesh. This “disease” takes shape in all apple growing regions of the US and seemingly has a few variants:
Caused by a combination of genetics, the fruit being mature or overly mature, and sunscald due to intense heat.
Low calcium in your soils (which could go back to genetics since there are some calcium hungry cultivars, like Albemarle Pippin, which is known for watercore)
Why is it considered a disease? The brunt of it comes down to long-term storage. Apple packing houses aren’t able to store the apples with severe watercore because the tissues will eventually start to break down, causing the flesh to turn brown (and thus marked as unsaleable). Another reason why it’s a bit of a bother to the apple industry is detection. Aside from some relatively recent research on detection methods, watercore has remained undetectable by the apple industry without the use of a knife (or teeth) to cut into the apple.
Like with the other apple diseases affecting the US, those with watercore are deemed as waste and dumped. In my affinity for looking at common diseases as heroes of value-added products rather than boons to the established industry, I’m excited about watercore. Here’s why:
The area above that looks water-soaked is actually where the apple has flooded its air spaces with a solution of sorbitol, a non-fermentable sugar alcohol which is not technically a sugar. According to Claude Jolicoeur’s Book, The New Cider Maker’s Handbook, sorbitol has a sweetening effect that amounts to about half the effect of white sugar. This means that when a cider or perry (cider made from pears) is fermented dry (the yeast eat almost all of the available sugar and convert it to alcohol), the presence of sorbitol would still have a sweetening effect on the dry cider (because it doesn’t ferment).
The idea of a completely dry cider with a nice, fruity, slightly sweet finish is very appetizing to me and happens to fall in line with my low-input management thoughts from fruit to bottle. Here’s my thought process (and some background story) on this one:
A long time ago, I was helping out in a cider house and they were sending a finished cider through a sterile (sulfited) filter to both strain the yeast from the bottle, but also to prevent any yeast that managed to slip through from reproducing. I was asked to taste the water being sent through the filter to detect the sulfur taste and the very moment when that sulfur water hit my lips, I was struck with an immediate and very scary asthma attack. That day I learned that I’m in the 1% of Americans who are actually allergic to sulfites and ever since, I’ve been a canary in a coal mine with respects to unbound sulfites in alcohol and suffice it to say, I’m not a fan of the additive. It has ruined many a cider/beer/wine for me due to my lungs closing up.
But why the use of a filter soaked in sulfites in the first place? When a cider is fermented dry, there is little fear of the cider/bottle of cider becoming unstable because all of the sugar in the cider has been consumed and turned into alcohol. If cider is bottled and has both alive yeast and sugar, the cider will continue to change in taste as the yeast convert the sugar to alcohol and more carbon dioxide is being created, which has been known to cause exploding bottles. In this situation, the sterile filter was being used because the cider was going to be backsweetened (the addition of sugar after fermentation) with apple concentrate to give the final product some sweetness (Americans love sweet). To recap: Backsweetening + yeast= off flavors and potential explosions. Backsweetening + filter + sulfites= a sweetened cider with less fear of re-fermentation.
What does this have to do with sorbitol and watercore? A higher presence of sorbitol in a cider means my cider can be fermented completely dry (free of sugar) while maintaining a minimal sweetness without fear of re-fermentation. Eliminating this fear of re-fermentation means that I can eliminate sulfites from the back end of my cidermaking process.
Watercore= Higher Sorbitol Content= Residual Sweetness in a Dry Cider With Less Chemical Inputs. ding. Ding. DING!
Ok, so let’s say that I’m sold on experimenting with this sorbitol/cider thing and I want to grow fruit in order to make this product. Being in the South, I have a lot of hope for achieving such a thing because the causal agents are: Intense heat, lots of sun (sunburn), low calcium, droughty conditions, and genetics.
In designing an orchard and keeping sorbitol production in mind, I would entertain the idea of going towards more of a dwarf set-up, perhaps even a trelli$ set-up on a southwestern facing slope. We’re talking steaming hot, dry, with the trelli$ed fruit being exposed to intense sun. On top of that, the apple system would be on irrigation which would allow you to regulate the amount of water and when to apply it. I’d also layout the orchard in a way which would drain quickly (maybe even a keyline design ;-)). Next, I’d choose varieties which are prone to watercore and also those that tend to hang on the trees rather than drop (which is a good genetic trait for apples in the South, anyways). Apples heading towards being overripe are at risk of watercore, so those that hold on are perfect candidates.
If you wanted to experiment with trying to intensify sunlight into a non-trellised tree, I would still try and have super quick water drainage off your site and have a SW aspect, but you could also try some extreme things like spraying all the leaves off your tree in late summer. I’ve done this for reasons of reducing vigor by using a 501 biodynamic prep, which I sprayed in late summer and managed to burn a BUNCH of the leaves off the tree…on purpose. I think the trick with this is in having a very vigorous tree and also determining the point of no return for apple ripening (if such a thing exists). The spray I applied in mid-August slowed the ripening scheme, which doesn’t help my sorbitol thoughts. However! It makes sense to me that reducing the leaf load on the tree would certainly help the sun scald situation.
I’ve never heard of anyone trying to grow apples with watercore on purpose, but why not? In straying from dessert fruit growing, managing for a certain product like cider could give regions like the South a distinctive taste in their products. We often think about this in terms of varieties and landraces, which are certainly a part of it. But let’s try and capture our environment and create a truly unique product which describes our place in every way.
*This essay has been in the works for far too long and I decided to push it through today. I’ll likely go back over it an link to things stored on my computer and correct spelling/grammar.*
Bruised and scabbed apples have more antioxidants and sugars because they’ve fought off natural stressors.
Grocery shoppers don’t generally make a beeline to the scabbed and blemished apples. But maybe they should. New research shows that trauma to the fruit—stresses from fighting heat, bugs, and fungus—forces apples to produce antioxidants such as flavonoids, phenolic acids, anthocyanins and carotenoids. And these compounds have all kinds of nutritional value.
A spin-off article from yesterday’s NPR article on eating ugly fruit, this time on weather.com! I’m so psyched this is getting attention. It’s only the beginning!!
Let’s face it: ugly fruit gets a bad rap. It’s often left behind at grocery stores and sold at steep discounts at farmers markets. More often than not, it gets tossed on top of an ever-growing pile of wasted produce.
But it turns out, these ugly fruits are fine to eat – and they may even be more nutritious.
Unsightly scars on the outside of fruit might reflect higher nutrition within.
Daniela White Images/Getty Images
When orchardist Eliza Greenman walks through a field of apple trees and gazes upon a pocked array of blemished and buckled fruits — scarred from fighting fungus, heat and pests — she feels a little thrill of joy. “I’m absolutely infatuated with the idea of stress in an orchard,” says Greenman, who custom grafts and grows pesticide-free hard cider apples in Hamilton, Va. These forlorn, scabbed apples, says Greenman, may actually be sweeter.
Hugh Ermen was one of the UK’s most successful modern apple breeders. He has raised Scrumptious, Red Devil, Winter Gem, Limelight, Herefordshire Russet and many others. He a leading exponent of the technique of growing apple trees on their own roots – rather than the standard practice of using dwarfing rootstocks. This is a copy of his work based on the experience gained over 25 years propagating and fruiting own root fruit trees of many varieties. Many fruit growers with long experience will know that growing a tree as naturally as possible is the best way.
Own root trees behave exactly as you would expect. Differences occur in trees on rootstocks due to the various degrees of incompatibility between stock and scion, which means there will be greater differences with dwarfing rootstocks.
Cropping will vary according to variety whether on own roots or rootstocks. I have found cropping more regular on own root trees, again as one would expect. Fruit size and quality at least as good but normally better. It has sometimes been suggested that we need trials to establish whether own root trees are better than trees on rootstocks. Having given this much thought, I would suggest this would be a waste of time and money. A trial would be influenced by the person conducting the trial whether intentionally or not. Of course apple trees grow well on their own roots, are the natural forests of apples on rootstocks?
The vigour of own root trees must be considered if you have little space. Triploid varieties will need more space than diploid varieties but I have found if they get the space they perform very well.
There are many basic techniques from planting to pruning which can be used to help control vigour, with cropping being the best control. For the newcomer to own root trees, I suggest starting with spur types and heavy cropping diploids. For the experienced person with enough space, the triploid varieties will not present a problem and you can always graft a fertile pollinator in the tree for the leader!
For the fruit tree nurseryman, the own root fruit tree should make propagation cheaper and reduce the risk of virus disease spread.
FRUIT ENTHUSIASTS – TRY OWN ROOT TREES!
Every variety of apple started life as a seed and in the past seedlings were selected growing on their own roots. Today the practice of apple breeders is to work the seedlings on to a dwarfing rootstock to bring them into cropping quickly. It is now well known, but often ignored, that degrees of incompatibility can exist between varieties and rootstocks, especially with the dwarfing rootstocks. It is probable that some potentially good varieties have been discarded in the past because partial incompatibility caused the seedling to give a poor performance on dwarfing rootstocks. A better but not necessarily quicker alternative would be to keep seedlings for assessment growing on their own root system. There are many well known ways which could be used to bring such seedlings into crop quicker.
As a general rule, the first seedlings to fruit from a batch of seeds are often flowering crabs, around year three to four. The next to flower are more likely to be good cropping diploid varieties. Seedlings that take six years or more to flower and fruit are usually moderate cropping diploid varieties. Triploid varieties are usually the last to flower and fruit which can take ten years.
Comparison of Cox’s Orange Pippin trees growing on M( dwarf rootstocks (left) and own-roots (right). The own-root trees have the same vigor as Cox on MM106 semi-dwarfing rootstock.
Experience gained over the last thirty years has shown that assessing seedlings grown on their own roots gives more information to the apple breeder. It is very useful to know the natural vigour of a seedling, its’ growth pattern, cropping habit, fruit quality and natural resistance to pests and diseases without any rootstock influence.
The realisation that a rootstock influence on a variety is greater than at first thought, gives grounds to have a collection of the main apple varieties propagated on their own roots. This would reveal the natural characteristics of each variety and although more land would be needed than a collection on dwarfing rootstocks, this would be offset by double the lifespan of the own trees roots.
Growing apples on their own roots is not new. A reference can be found in the Transactions of the Horticultural Society of London where Mr Arthur R Biggs F.H.S., read a paper in February 1807. Only a few apple varieties could be propagated by cuttings, until research showed the way with use of heated propagating bins and micro propagation. Further progress with own root apple trees has been very slow, due to the major cut backs in Research and Development.
However, there is now enough experience with own root apples to make further development work worthwhile and the breeding of compact varieties to exploit the benefits and overcome the drawbacks.
Advantages of Own Root Trees
Better tree health- Each variety differs in its precise nutritional requirements which can easily be achieved naturally, by growing a variety on its own roots. There is a difference between the uptake of nutrients by a rootstock and the exact requirements of the scion variety worked on it. This mismatch can lead to a reduction in the health of the scion variety and fruit quality.
Red Devil on own roots, cropping heavily
Better fruit set.
When a variety that comes into growth early is worked on a late starting rootstock and flowers before the rootstock becomes active, poor fruit set will result.
Better fruit quality and storage life
Better resistance to pests and diseases
Excellent for pot culture
Disadvantages of Own Root Trees
No rootstock vigour control
Insufficient development work at present on large scale propagation of own root trees.
A Vigour Guide To Own Root Trees
Dwarfing – semi dwarfing (M9 – M26) Diploid compact spur type varieties and clones (e.g. Starkspur Golden Delicious)
Medium Vigour- The majority of diploid varieties (e.g. Cox’s Orange Pippin)
Vigorous- The majority of triploid varieties (e.g. Bramley Seedling)
Tree Management Techniques
There is plenty of scope for innovation, especially for the amateur. The following drawings of possible tree shapes and planting systems will stimulate further innovation.
45 degree Plant
Zig Zag Stem
No tree stakes required. Tripod trees withstood the hurricane in Kent without damage. Base of the triangle is 1m x 1m x 1m.
No tree stakes required. Tree vigour can be controlled by reducing or increasing the angle of the trees. Base of the square is 1m x 1m x 1m x 1m.
Posts and wires needed for support. This system requires some experience of spur pruning
Central tree is a Wijcik type pollinator. An alternative is to graft a pollinator variety directly on to the tree.
3 x Cox’s Orange Pippin own-root trees grown as a tripods to control vigour (1m between each tree) – 1998
Techniques to encourage early cropping
Plant well feathered maidens or possibly 2yr old trees
Plant at an angle of 45 degrees
Tying down branches near horizontal
Minimum winter pruning
Bark ringing (not in year of planting)
Bending over and tying down leading shoot in late June
Grassing down orchard
Careful use of fertilisers, especially Nitrogen
In general, flowering and harvesting times will be similar to trees grown on MM106 rootstock. Fruit shape will be typical for the variety (MM106 produces a slightly more conical Cox fruit).
The culture of own root trees
The Site The same as for trees worked on a rootstock
Own root trees do not require the rich deep soils which are desirable for trees on dwarfing rootstocks. Cox’s Orange Pippin is sensitive to soil pH and will not tolerate a pH below 6.5 and grows better in neutral soil.
The Prejudice Against Own Root Trees
Many Growers have experienced scion rooting in orchards of trees grown on the dwarfing rootstocks M9 and M27. These trees become vigorous as a result of scion rooting and receive hard pruning in winter to keep them confined to their allotted space. This practice causes the trees to grow more vigorously and become unfruitful. The conclusion reached is that trees on their own toots are vigorous and unfruitful, which they can be in these circumstances.
3 mature Cox’s Orange Pippin own-root trees grown as a tripod
Some research workers, but not all, feel that own root trees are a retrograde step, after all the research that has gone into rootstocks. On the other hand, research work has made own root tree propagation a practical proposition and both England and Europe trial orchards were planted, but cutbacks in research terminated this work. Extended private observations of own root trees has indicated that further development work is worthwhile, especially with organic growing in mind.
Views have been expressed that uniformity of trees on rootstocks is much better. The author has not found this to be correct. Uniform planting material produces uniform trees, whether on rootstocks or own roots.
Years ago, some plum orchards were grown on their own roots and were re-propagated from suckers. This lead to a steady decline due to virus and other diseases, which were little understood by management at the time. With all fruit propagation it is essential to use virus free material whenever possible.
Reliable information from home and abroad has stated that Cambridge Gage used to grow and crop better on its own roots than worked on a plum rootstock. This is now being checked with trees growing on their own roots. Trees of Victoria are also being observed on their own roots.
The Propagation Of Own Root Trees
No large scale production of own root trees exists at the present time.
This should be the fastest method for large scale production. It has to be carried out with skill and care, to avoid the production of ‘OFF’ types. Trees raised in this way experimentally, have initially been more vigorous and slower to crop than trees from hardwood cuttings. No doubt with more development work these slight drawbacks can be overcome.
Variable results have been obtained with hardwood cuttings placed in heated propagating bins. The optimum base temperature has to be worked out together with the air temperature of each variety. For example, Bramley Seedling roots well if cuttings are taken at leaf fall and placed in a propagating bin with base heat of 25° C and in an air temperature of 20° C. Many other varieties rooted with an air temperature around 5° C. There was also marked seasonal variation in rooting. The use of a rooting hormone (IBA) was essential with most varieties. The method is only used for easy rooting subjects commercially, such as rootstocks. New simpler techniques are being evaluated by F.P. Matthews of Tenbury Wells.
Nurse Root Cuttings
This method has proved reliable using M27 nurse roots. Many if not all, varieties can be rooted by this method with or without rooting hormone. Giving base heat in a propagating bin gives speedier rooting, or placing unheated bins under plastic or glass. Placing the cutting bins outdoors can also be successful. This method is used initially to get a variety on its own roots.
The Katy apple tree on it’s own roots, kept to the same size as M9 trees by allowing very heavy cropping.
Roots from preferably young trees, about pencil thickness, can produce a whip about 50cm tall in one growing season in an outdoor bin. Feathered maidens have been produced from roots if the bins are placed under polyethylene or glass. Outdoor benefits from insulation against excessive cold or hot ambient temperatures. Bins are best raised off the ground and placed in good light conditions. It is an ideal method for small scale production.
Propagating Pears, Peaches, Plums and Cherries
The same methods described for apples can be used for pears and plums. The author has limited experience with peaches and cherries. Peregrine peach raised by semi-hardwood cuttings under mist cropped very well indeed. A nurse rooted (using Colt) Stella cherry grew and fruited well. Peach root cuttings from Peregrine tried on a very small scale have not been successful. Roots from Colt cherry rootstocks grow very well.
Future Potential For Own Root Trees
The full potential for own root fruit trees will only be revealed when we have gained sufficient experience of the best methods of propagation and culture. Gaining this experience will be exciting for the dedicated fruit enthusiasts be they amateur or professional. The biggest difference in fruit quality and flavour between own root trees and rootstock trees will be found between own root trees and trees on dwarfing rootstocks.
Trees growing on their own roots may not crop more heavily or have better fruit size than trees on M9 although better cropping and fruit size has been apparent with some varieties. What can be virtually guaranteed with the experience gained so far, is more regular cropping and better quality fruits which have a better storage life. Fruit flavour could well be more intense and with generally more seeds per fruit, better fruit shape. In the end it will be the grower who by his skill, can manage own root trees and obtain the full potential.
Pruning Guide for Own Root Apple Trees
Cox’s Orange Pippin own-roots trees grown as tripods to control vigor
The vigor of an own root apple tree depends on the variety or clone, not on a selected rootstock. The best way to control the vigor of an apple tree, whether on its own roots or a rootstock is by cropping.
The basic vigor range of rootstocks is:
Dwarf – semi dwarf Rootstocks M27, M9 and M26
Medium vigor Rootstocks MM106, M7 and MM111
Vigorous – very vigorous Rootstock M2, M16 and M25
The vigor of named fruiting varieties can also be grouped into three categories:
The vigor of named fruiting varieties can also be grouped into three:
1. Dwarf – semi dwarf
All Wijcik (Ballerina) varieties
Starkspur Golden Delicious
Granny Smith Spur
Lord Derby Spur (culinary)
Cox Spur Type
Discovery Spur Type
2a. Medium vigor (Dessert) mainly diploid varieties
St. Edmund’s Pippin (russet)
Cox’s Orange Pippin
2b. Medium vigor (Culinary) mainly diploid varieties
Rev. W. Wilks
Lane’s Prince Albert
Vigorous – very vigorous -mainly triploid varieties
Pruning apple trees
This is carried out in two stages.
1.At planting time to train the tree to grow into the desired shape.
◦ Pyramid and Spindle Bush
◦ Bush 3′ leg
◦ Half standard 4 1/2′ leg
◦ Standard 6′ leg
◦ Centre Leader
◦ Tripod (three trees)
◦ Step over
3. Growing tree
◦ To let light and air into mature trees to encourage flower buds,
strong mature flowers and good quality fruit.
◦ To cut out damaged or diseased wood.
◦ To regular cropping by removing excess fruit buds especially by
thinning complex spurs.
◦ To renew branches.
◦ To retain a balanced (stable) tree.
◦ To allow access for picking fruit.
◦ To maintain tree in space provided.
FAILURE to prune mature trees will lead to:
Tangled and overcrowded growth.
Excessive cropping which increases the risk of biennial bearing.
More likelihood of unbalanced growth leading to a greater risk of tree
instability, especially when carrying a heavy crop.
Growth characteristics of apple trees
Two kinds of buds can be found on apple shoots/branches. On one year old shoots there will be small wood buds. In the second year some wood buds will fatten up and become fruit buds. The terminal bud at the end of the shoot will normally continue the shoot extension although in a few varieties (tip bearers such as Worcester Pearmain) the terminal bud will often form into a fruit bud, and fruit in the 2nd year. In the third year flowers will emerge from the fruit buds and if pollinated successfully, the flowers will grow into apples.
The fruit buds on two year old wood are in reality very short shoots calledspurs. Some varieties called spur types grow further spurs as the apples are growing, instead of shoots. Normally each spur will terminate in a fruit bud. After a few years the spurs become numerous and the quality and size of fruits formed on them deteriorates due to competition. It is then necessary to thin the spurs in the winter, so that competition is reduced. Apple varieties forming spurs readily are the easiest to manage on their own roots, as much as of the natural tree vigor foes into the production of apples. All the other varieties need to be pruned to encourage a good balance between growing and fruiting.
Time of pruning and effect
Pruning in winter reduces the aerial parts of the tree but not the roots. The effect will be to increase the vigor of shoots and branches and discourage formation of fruit buds. Winter pruning is ideal for trees that have too many fruit buds and little extension growth. Pruning young trees where growth is needed and directed in to forming the tree, rather than fruit production, is carried out in winter.
When the trees are leafless in the dormant winter season, damaged, diseased or congested growth can easily be seen. If the tree is very vigoros, winter pruning is less desirable. In this case it is best to leave pruning until growth in the spring starts, or prune directly after picking and before leaf fall.
At this time of year, pruning reduces the number of leaves which manufacture food materials. Summer pruning therefore reduces the vigor of the tree and improves the cropping potential. Summer is an ideal time to remove strong vertical shoots which are generally unfruitful and shoots growing underneath branches which get heavily shaded.
Pruning – apical dominance
The highest bud on a shoot, pruned or unpruned will be dominant and will grow out stronger than any other bud. The strongest growth will be at the top of a branch or tree. When growing a centre leader tree (a tree with a central trunk up to the leading shoot) you control growth using the leading shoot of the stem. Cutting back the leader will increase growth in the lower branches. Leaving the leading shoot unpruned will reduce vigor in the lower branches. The harder the tree leader is pruned (ideally down to a well placed weak shoot) the greater the vigor increases in the lower branches.
Pruning is best demonstrated in the orchard. Failing that, watch the response of the tree to pruning and react accordingly.
This is exactly what it says. Pruning to regulate the tree growth and cropping. Basically a tree is pruned to get balanced growth and branches to carry fruit in good light and air. Vertical growing vigoros shoots are usually unfruitful and shoots growing downwards underneath a branch get heavily shaded, both types should be removed. Shoots growing out from the sides of branches are ideal for carrying fruit. When these side shoots have grown too long they are best cut back to the main branch with a sloping cut, leaving more stub underneath to encourage a renewal shoot to grow from the stub at a nice wide angle.
The basic bush tree and centre leader tree should have about four main branches, arranged around the tree for good stability. The height of these branches from the ground will depend on the type of tree being grown. Bush trees have branches around 3′ from the ground, half standards 4 1/2′ and standard trees 6′ from the ground. Centre leader trees normally have their main branches at waist height for easy harvesting of the fruits. Branches above these are renewed before they get too big, by cutting them back to the trunk with a sloping cut to avoid too much shading of the main branches.
This method of pruning is mainly used for cordons, espaliers and other more formal shaped trees. The object is to create fruiting spurs close to the stem and main branches. Some varieties form spurs very easily (Starkspur Golden Delicious) and are known as spur types whilst others range from easy to difficult.
The difficult varieties are usually tip bearers (e.g. Worcester Pearmain) and vigoros triploid varieties (e.g. Bramley Seedling). Spur pruning is mainly carried out in the summer and involves cutting back shoots growing directly from the stem or main branches to encourage fruit buds to form near the stem or branch. There are many ideas about how best to achieve fruiting spurs close to a stem or branch. The vigor of the tree can be used as a guide.
Weak growing trees
Prune young shoots when they reach 9″ and cut back to an underneath bud around 6″.
Moderate vigor trees
Prune young shoots when they have reached 12″ back to an upward growing bud around 9″. The shoot will almost certainly grow out from that top bid and can later be pruned back to the underneath bud behind the top bud which has grown out at a better angle.
Orange Pippin Own-Root Trees, 1987
Prune young shoots that have reached 18″ back to top bud around 12″ then continue as for medium vigor trees. This can only be a rough guide and timing will differ due to weather, culture etc. Watch the tree’s response to pruning and adjust accordingly. Ifthe tree has not responded with fruit buds near stem or main branch it is best to cut the shoot back to the stem or branch with a sloping cut to encourage a further shoot to grow out at a wide angle and start again.
Grafting shoots into strategic positions
If all else fails, there is a graft that can place a shoot in a branch or stem, provided the stem or branch is reasonably thick. This involves collecting dormant one year old shoots in early February and placing them upright in a pot of sand to a depth of 4-6″ which is then placed in a cool shady part of the garden. Alternatively, shoots can be placed in a polythene bag (not airtight) and stored in the vegetable compartment of a refrigerator. In April when the sap rises and the bark will lift, the stored shoots can be used for slit grafts in the bark. This enables shoots to be placed in ideal positions on stem or branch. Length of grafts depends on the vigor of the tree. 4″grafts for weak growing trees, 6″ for moderate vigor trees and 8-9″ for vigorous trees. These grafted shoots normally form fruit buds easily.
Pruning should not be regarded as an isolated operation but as part of the tree culture and taken together with soil management and cropping. For more detailed information about pruning, the R.H.S. Wisley Handbook on Pruning Hardy Fruits by Jack Woodward can be highly recommended.
H.F.Ermen. A.H.R.H.S., N.D.H.
Mr Ermen died in 2009. In March 2010 the UK Royal Horticultural Society recognised Scrumptious, one of the most popular varieties raised by him, with the Award of Garden Merit – the first such award given to an apple variety for more than 10 years.