Rootstocks: Do they impact flavor?

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.


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.


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?


watercore: a natural additive for hard cider in the south

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:
Photo Credit to Adams Apples
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:
  1. Caused by a lack of water or droughty conditions
  2. Caused by a combination of genetics, the fruit being mature or overly mature, and sunscald due to intense heat.  
  3. 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.*



Nature’s Secret: We May Have Totally Underestimated Scarred Fruit


A spin-off article from yesterday’s NPR article on eating ugly fruit, this time on! 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.


Read more: Here!

Beneath An Ugly Outside, Marred Fruit May Pack More Nutrition

 NPR wrote an article about #eatuglyapples AND IT ALL STARTED WITH THIS BLOG! 

Unsightly scars on the outside of fruit might reflect higher nutrition within.

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.


Read more, HERE.

Cider And Heirloom Apple Vigor: An Hypothesis

Recently, I was on the phone with a mentor and we were discussing hedgerows (my new pet project, aside from brewing all sorts of alcohol). With some of the species I mentioned, I was told that livestock would eat them down to nothing and render the hedgerow useless. After having a few tree species rejected, I frustratingly asked: “What if I planted my hedgerows with invasives like multi-flora rose, then?!”

Without any hesitation, my mentor said: “Invasives like multi-flora rose are very delicious to many animals, like my goats.  You might be suggesting invasive plants for your hedgerow because they are vigorous and seem to outcompete everything else, but try to think about vigor from another perspective. If plants with high vigor are also the most sought after by animals, don’t you think that vigor might be an evolutionary trait to survive browse?”

This is the first time I’ve heard this perspective on invasives and I’ve really enjoyed thinking about it. After some minimal research, I found out that the subject is still debated today by ecologists as the “plant vigor hypothesis.” Generally speaking, vigorous plants have higher nutrient densities than non-vigorous plants, so herbivores are more prone to eat them. However! If the very vigorous cultivars are able to put on a bunch of girth, many herbivores aren’t able to eat the whole thing because of their jaw size.

This, of course, has got me thinking about apples. Here’s why.

In many essays on this blog, I’ve talked about how I consider many cider and heirloom cultivars to be very vigorous as compared to most of the grocery store cultivars. Vigorous cultivars are harder to prune, occupy more space (so less trees per acre), have issues with vegetative vs fruit bud proportions, etc. In general, they are harder to grow.  After reading more about this “plant vigor hypothesis,” I wonder if there is a connection between vigor and nutrient density in apples cultivars?


From an evolutionary standpoint, a correlation between vigor and nutrient density makes sense to me. Many wild crab apples in the US have much higher tannins (aka polyphenols, which =nutrition density) than cultivated varieties. This is from the many lifetimes spent co-evolving with insects and herbivores who are trying to eat them. From observing crabapples in the “wild” and planted in landscapes, it seems as if many trees have low vigor and perhaps this is because they have evolved to have an unpalatable deterrence for animals and humans alike?

In hard cider, many of the wild crabs are too much for our palates to handle and though very nutritious, they will cause a harsh and likely negative consumer experience. So what have we done? Over time, cider drinkers/makers/apple growers have selected cultivars to grow which are palatable to the consumer, but also contain enough tannins (or polyphenols, or natural defense) to give the cider some substance.  Could it be that in selecting not-so-astringent apple cultivars for eating/drinking, we’re unknowingly selecting for more tree vigor? If the apple cultivar hasn’t evolved enough to deter herbivores through astringent taste, then do genetics dictate that it must rely on vigor to survive? 

These sorts of questions make me excited and I’ll keep learning about these processes in order to try and uncover different management ideas that don’t involve regulating vigor through the use of dwarfing rootstocks, black magic hormonal potions like Apogee (which converts vegetative buds into fruiting buds), and planting in light soils. All of those management aspects, I suspect, are making the vigorous cultivars less vigorous/more fibrous/less nutrient dense.

Thoughts to be continued, but in the meantime here are a few off the top of my head:

Thought 1: Pruning extremely vigorous varieties like an herbivore in order to get faster fruit set?

Thought 2: Continuing to fruit explore to find mixes of wild x cultivated which hit high nutrient densities, palatability, and lower vigor.  (I’m writing a fruit exploring book about how to do this at the moment)

Thought 3: Making crabapples a significant part of my home breeding program.



Stress: The New Bittersweet? (A Radical Orchardist Part 2)

It seems like it has rained every day for the past month in the Champlain Valley of New York and Vermont. Combined with 70-80 degree temperatures, the fungal population couldn’t be happier. It’s like one continual fungal feast over here, and I couldn’t be more psyched. Why? Because I’m absolutely infatuated with the idea of stress in an orchard.

Screen Shot 2015-06-30 at 4.43.12 PM

In A Radical Orchardist: Part One (which I encourage the reader to read before pursuing this essay), I re-introduced my thoughts about how apple scab, a fungal disease, increases the brix (sugar content) of the apple, which translates into a higher alcohol content once fermented. For hard cider purposes, I thought, perhaps we shouldn’t be spraying-late season fungicides for cosmetic fungal diseases like apple scab, since lingering fungicide residue has been known to kill the ferment (the yeasts) in the wine and cider realms. I also re-introduced the idea of managing apple scab as a value-added disease for cider apples, a thought that is about as radical as it gets these days in the apple world. A thought that I’m still excited to explore and understand in order to embrace it or dismiss it.

This year, I’ve been actively looking for scientific research on the effects scab has on apples, from a nutritional standpoint. I want to know how the apple reacts to scab; What does that fight look like? Does a stressing agent like apple scab bring about super fruits? This research is slow, mostly due to the fact that I don’t have access to any scientific journals, but it’s progressing and has me optimistic. The following is a report on my findings and thoughts.

Stress: The New Bittersweet?

My journey started when I found a paper about the effects of apple scab on the peel of an apple. The article, which can be found here and simply broken down here, stated that a peel covered with scab lesions is higher in polyphenols than one not covered in scab. What’s the big deal? Quite a bit, actually. This is a big deal. Screen Shot 2015-07-01 at 3.27.42 PMScreen Shot 2015-07-01 at 3.28.21 PM

Screen Shot 2015-07-01 at 3.28.12 PM

Phenols, such as chlorogenic acid (as seen in the top graph), are classified as antioxidants, meaning  that they tend to prevent or neutralize the damaging effects of free radicals in the body. Free radicals are chemicals that have the potential to cause damage to cells and tissues in the body.  Many of the phenols mentioned in the paper above are related to resveratrol (the polyphenol found in red wine which got a lot of news a while back for making wine drinking a life-saving activity). When researched in the skin of non-scabby red apples (aka: what you see in a grocery store), they were found to contain powerful antioxidant capacities, along with anti-cancer, anti-inflammatory, and cardio-protective properties.

Now, take those phenolic values from the skin of the non-scabby red apple and multiply them by at least 3+ times. That new value is one coming from an apple with scab infection. To further push this point, this article suggests :

The way in which orchards are managed can influence the amount of phenolics, as shown by Veberic et al. (2005), who reported that organically grown apples had somewhat higher amounts of phenolics as compared with traditionally grown apples. These authors concluded that this is probably because organically grown apples face more stressing conditions, for synthetic fertilizers and pesticides are not used.

Folks, this is superfood status and at the very least, people should try to source ugly organic apples and eat the peels. Research says that doing so might save your life someday.

Now, to project these findings onto cider…

What makes a cider apple a cider apple? The quick universal answer most people know is that it’s in the tannin. Tannin is a collection of phenols such as chlorogenic acid, phloridzin, epicatechin and the procyanidins (source). Only the procyanidins are considered “true tannins” because they have the ability to tan things like animal hides and give the drying sensation we recognize as astringency (aka: the sensation you get when you stick an acorn in your mouth). For the most part, bittersweet apples have the most tannins, or phenolics, and dessert apples have the least.

A bittersweet apple, taken from this Serious Eats article, is described below:

If there is one style of apple prized above all others by American cider makers, it’s the bittersweet apple. Affectionately referred to as a “spitter,” these apples are low in acid, high in tannin, and impart the classic flavor of finer French and English ciders. At first bite, most would consider bittersweet fruit inedible. But what is ill suited for the fruit bowl is ideal for the cider press.

For the most part, America’s high acid, high sugar apple crop provides all the fuel for fermentation and puckering power necessary for a great cider. But what that fruit lacks is tannin—the molecules that impart astringency and provide a cider’s texture—and bittersweet apples fill this void.

Ignore the yellow highlighting, and the column about gelatin

I hope your wheels are turning like mine were, but in case not, let me break it all down for you.

Cider apple varieties are known for their higher levels of phenolics, because those phenolics (aka tannin) distinguish them from dessert fruit. Those phenolics involved in making a cider apple a cider apple are also the same phenolics that increase in concentration when the apple is stressed with apple scab. If you refer to Figure 1 above, you’ll also see that in addition to high levels of polyphenols, a bittersweet apple is one with a higher brix. Let me remind this audience that this whole Radical Orchardist series started with the deletion of an article I wrote about how apple scab increases the brix in apples.

I’m no chemist, but it seems to me that stress has the potential to send some dessert varieties into the realm of a bittersweet. Now, how about stressing a cider apple? Is the increase in phenols due to stress worth it to the cider maker and the consumer? This study says that phenols in hard cider are absorbed, metabolized, and excreted by humans. Meaning, we’re getting the nutrients.

Screen Shot 2015-06-29 at 10.51.33 PM

phenolic content of apple leaves, healthy vs infected with scab.

It makes sense to me. When stress occurs, the apple’s response is to pump the site of infection/attack full of phenolics (see graph to the right) . Look no further than your forest’s edge to find wild, highly evolved, inedible tannic crabapples that serve my point. The crabapples have evolved to contain these phenolics without provocation. The lesser-evolved dessert varieties, however, may need to be provoked through varying degrees of stress in order to produce a more nutrient-dense product, or one that more resembles a bittersweet cider apple.

What does this mean for management? Back in the first A Radical Orchardist essay, I irritated a few folks with the question:

What is a cider apple? Sure, you can have all the old French and English varieties like Dabinett, Frequin Rouge, Tremletts Bitter, Norfolk Beefing, etc, but if they are managed the same as dessert apples…are they really cider apples? I don’t think so.

And I still don’t think so. I believe that growing cider apples requires a completely different mindset than growing dessert fruit in order to make high quality, nutrient-dense, healthy organic hard cider. To me, a part of being a cider orchardist involves learning how to balance stress within the orchard through organic means. What do I need to give the tree in order to replenish the expense of fighting off an infection? What is the tipping point of too much stress? I whole-heartedly believe that these, plus many more, are the questions we should be asking. Imagine a world where the value of an apple comes not from its looks, but from its nutrient content. That’s what I’m aiming for with stress, and I believe there is value in that.

Please, those of you who are researchers…prove me wrong. I have admitted to the fact that I’m no chemist, and without academic ties, its completely reasonable that my understanding is flawed from the free book snippets and articles I find online. Send me a response with accessible PDFs, I’ll make sure to post it in a follow-up essay with reasons why I agree or disagree. Hopefully some great questions will come out of it and some university or private foundation somewhere will want to investigate.

In the meantime, the take home message is to #eatuglyapples and #drinkuglyapples. Embrace the scab, avoid the rot and challenge the status quo.

Postscript: Earlier in this essay, I included the following phenolics to define tannin. They were chlorogenic acid, phloridzin, epicatechin and the procyanidins. From this article, it states that apples infected with scab had:

  • 6.5 times more phloridzin than a healthy apple.
  • chlorogenic acid can be found in the first graph of this essay
  • epicatechin levels are in the following graph:
  •  Screen Shot 2015-07-01 at 7.26.50 PM
  • procyanidans are flavanols, which are widely cited by research papers to be the reason why some apple varieties are resistant to scab.