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.

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:

1867:

1871:

1873:

1889:

 

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:

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“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?

 

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On their own roots

A long time ago, orchard and nursery people often grafted scions from known cultivars onto dug-up root pieces from apple trees. This was one of the ways in which orchardists and nurserypeople were able to propagate specific varieties rather than getting something completely random from seed. The other way was to graft onto existing trees (called top-working, or top-grafting) or onto rootstock produced by planting seeds.

 

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Root grafting (on purpose) has largely disappeared as a horticultural practice due to the rise of clonal rootstocks. We are now able to decide what size tree we want and how soon we’d like the tree to bear apples, which has been the primary cause for eliminating old “standard” sized trees from the landscape.  In fact, you wouldn’t believe how many old orchards I visit where the owners have been told by the extension service to cut down the old orchard and plant high density apples…

It’s true that high density apple systems have proven themselves to make more money than trees able to stand up by themselves (in a high-input dessert fruit market), but I’m not totally sold on that model when it comes to growing process fruit for cider, pies, etc. I’ve run the numbers (which I’ll share soon) and you’d have to plant many, many acres of apples to make it work out financially (if you were to sell wholesale and not turn them into your own value-added products). After it’s all said and done, you’ve got an orchard that can live for 25 years on a spacing that makes it hard to “stack functions,” or grow other crops/animals within your system to have a diversified income (which is necessary for me)

*Disclaimer* I have heard from a smart orchardist outside of Pittsburg who is growing black raspberries on the same trellissing as his high density apples with wild success.

 

Eliza fameuse tree

Back to root grafts:

  • Yes, these trees are often times very large compared with apple trees grown on clonal rootstocks.
  • Yes, they are going to take 10-10+ years to bear fruit.
  • Yes you can only fit 55 trees per acre…

But…

  • I’ve seen a lot of old apple trees in my lifetime, like the one pictured above which is over 200 years old! That tree was root grafted and, as a result, on it’s own roots.
  • The Fruit Explorers, a group of which I’m a founding member (along with Pete Halupka of Harvest Roots Farm and Ferment), traveled around the South last year looking for all sorts of apple trees. By far, the healthiest trees we found were those on standard rootstock or growing on their own roots. We were in the hot, humid, zone 7a-8a South which is known for all sorts of rots, fireblight strikes, fungal infections…you name it. And the trees that looked the best were the big ones. All of this observation caused me to believe that we probably have the best chances of growing low-input trees if they are on big roots.
  • I can grow other crops in the rows between the trees. I can graze animals. I can have a diversified income stream while waiting for the orchard to come into bearing and for the canopies to narrow the rows.
  • The trees will be of uniform size if you are root grafting the same cultivars within the row
  • Who’s to say these trees won’t each drop 100 bushels of apples a piece?

Basically, all of this is to say: I think that root grafting isn’t such a bad idea for an orchard if you have the space and the time.  I’m crossing my fingers that I’ll have the space in the next couple years, so the remainder of this blog post is about my thoughts and actual practices of root grafting…

This year, I ordered 1000 southern crabapple trees from the Maryland State Nursery (Malus angustifolia). I decided on M. angustifolia because I’m in the South and these crabapples are better adapted to this hot and humid climate. Also, I had already decided that I wanted standard sized trees, so why not use them as a rootstock?

Well, after I ordered them I did some digging and realized that M. angustifolia, which on average is not that large of a mature tree (maybe 20 feet), would probably not be able to handle the vigor of the heirlooms and cider varieties I wanted to graft. Across the boards, from writings I found in the 1800s to anecdotal quips from friends and thoughts from mentors, it seems like the majority of these seedlings would only be able to handle the graft for a few years and then the top would eventually outgrow the bottom, resulting in death. The success stories I read involved topworking mature, already-in-the-ground-and producing-crabapple trees OR grafting onto crabapple stock from Russia. Russian crab stock is more vigorous and able to handle the older varieties and I’ve seen evidence of this in very old orchards in Maine, where the cultivar died out and the crab stock bolted upward.

Compared to the Siberian crabapple stock we ordered last year (Malus baccata), this year’s rootstock was tiny and we were left trying to figure out how we were going to graft it because on average, our scion is larger in diameter than above the root collar. That’s when I settled on the idea of root grafting.

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This is a larger example of a the M. angustifolia crabapple we received from Maryland.

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I use a foot powered saddle grafter much of the time to save my hands because I battle carpel tunnel due to repetitive orchard/nursery movements combined with being on the computer too much of the time.

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This is what we’ve done to many, many crabapple trees. We took the root, made a grafting cut (some whip and tongue, many saddle, some omega and some cleft). Roots are often difficult for me to graft because many of them aren’t straight, but squiggly. This is where the saddle grafter came in handy, or we employed the cleft graft.

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We left the scions larger when grafted. Usually, you only need a bud or two for grafting but I decided to leave 5-6 buds for reasons I’ll tell you about later in this post.

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Pictured above is the final product. We grafted the scion to the root, wrapped it with a rubber band to make sure the union was nice and tight, and then wrapped the graft union/rubber band in parafilm (wax tape) from top to bottom. Some of you might be thinking: A rubber band PLUS parafilm! That’s overkill! And it is, to an extent (though it is pretty much a guaranteed take if you are able to make your vascular cambiums line up). But here’s why we did it…

By itself, horticultural rubber bands will degrade in the sun and fall off the tree within a certain time period so you don’t have to worry about it girdling the tree. By itself, parafilm will also degrade/expand/drop off a tree later in the season without it girdling the tree. TOGETHER, however, your tree is doomed for girdling unless you manually get out there in the summer and cut it off in time. I learned this the hard way, folks.

Why are we using this rubber band/parafilm method for grafting a root when I won’t be able to cut it off due to it being buried in the soil? Well- the answer is this: I want the girdling. Before I put this all together for you, I need to go on a brief tangent (which connects, I promise).

Last summer, we visited with Jason Bowman of Horne Creek Historical Farm (one of the sites that has Lee Calhoun‘s entire collection) and he was kind enough to take us through the orchard. Every year, I notice something different about trees and during this particular visit, I noticed how tree form differs from cultivar to cultivar. This is nothing new, really, because I’ve pruned many different cultivars of apples and they are all different. But this time, my knowledge of what trees had better disease resistances combined/confirmed with Jason’s were overlayed with tree form. I started to notice how apple varieties like the Dula Beauty naturally had wide crotch angles, creating better natural airflow and therefore, less fungal problems because humidity wasn’t being trapped within the tree as readily as some other varieties.

Keeping this in mind, I’ve been wanting to return my most disease resistant cultivars with excellent tree form (wide crotch angles) to growing on their own roots because I think they will require less pruning down the road (which is one of the big arguments for going to smaller trees…less and faster pruning). I want to see what size these trees will be without interference of rootstock, how many bushels of apples these trees will bear, and I want to taste an apple on it’s own roots as compared to another rootstock. That’s why we’re grafting in a way which will eventually have the root girdled from the scion (by using the rubber band/parafilm method). Alone, it’s fairly difficult for an apple cutting (scion) to produce roots on it’s own, so that’s why we’re grafting it to the crab roots. I want this crab stock to be a nurse to the scion, keeping the scion alive and fed while it starts to produce it’s own roots, and then to die off!

We left the scions long on these roots (5-6 buds rather than 2-3) to give room above the graft union to plant the scion. We’re going to try out two methods for this:

1.) We’re going to plant the whole thing and leave 2-3 buds sticking out of the ground. There will be irrigation.

2.) We’re going to plant the root and the graft union, and then cover the soil with several inches of sawdust which will be under irrigation. The area where damp sawdust contacts the scion should encourage root growth into that space.

When the time comes for digging these trees up and transplanting them, in a year or two, we may cut off the crab root if it’s still attached and alive. We’ll see! Updates to follow whenever we dig these things up (starting in the winter of 2016/2017).

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the over ambitious apple farmer: grafting

As greenhorns (beginning tradespeople), we often have no idea about what we are physically capable of getting done in an hour/day/week/month/season. If there’s a will, there’s a way….right? Let me talk about that for a bit.

I thought my business (Legacy Fruit Trees) would pre-sell 500 trees this year. I pre-sold 4000 instead. “Not a problem,” I told myself…”I’m capable and competent, I sooo have this covered. ”

And so I started grafting. Do you know how long it takes me to graft 250 trees? 8 hours. That’s almost 2 minutes per tree and what I consider to be fairly speedy rate. Here’s the process:

1.) Acquire rootstock (I bought rootstock from Treco, Cummins, Adams County and Cameron Nursery). Rootstock determines the size of your tree (in most cases) and how many years to fruiting. I accepted orders on everything from “standard” rootstock (30 foot tall tree taking 10 years to fruit) to “semi-dwarf” rootstock (down to 12 feet tall taking 2 years to fruit). In a later post, I’d like to review these companies and the quality of rootstock I received, but for now we’re sticking with the basics.

2.) Acquiring scionwood. Scionwood is the most recent year’s growth on an apple tree (any tree you find desireable, you can clone and it all starts with scionwood and rootstock). The time to collect it is in the late winter, when the tree has gone fully dormant (all the sap in the tree is now down in the roots).

3.) Grafting tool. For me, I used the Graftech Manual Grafter by Ragget Industries (review to come later). In the past I just used a victorinox grafting knife, but since I prune for 2 months straight before grafting, I have to give my wrists and carpel tunnel a rest and went with the foot powered machine.

graftech manual grafter4.) Cut scionwood. Cut Rootstock. Stick them together so the vascular cambium  from each are making as much contact as physically possible.

Harrison graft5.) Wrap and seal. I wrapped with a rubber band and sealed everything up using Doc Farwell’s graft sealer. This is the most time consuming of the process and is also the most important. You don’t want your graft union to dry out. Many people used parafilm which will wrap and seal all in one, but it’s not tight enough for my needs with this grafting tool. It will work with other methods, though.

6.) Stick in moist sawdust/peat moss in a cool place and wait for bud swell.

Ok, that’s the quick rundown. Now, 2 minutes per tree…4000 trees…that’s 8000 minutes! 8000 minutes of doing the exact same thing over and over and over again.  At first this was a  lot of fun because grafting is really cool. It’s like putting frankenstein together, only less scary and ultimately ending in delicious fruit. This fun didn’t last very long, though. I started day-drinking beer around the time when my cuticles started to bleed (probably day 6-or-2880 minutes).  It was also really cold and as you can see from the picture below, my grafting shed was (it’s now remodeled) a bit breezy.

Grafting ShedSo I hired someone to help me. The guy showed up and showed real promise and I made the rookie mistake of paying him after 2 day’s worth of help. He never came back.

Then I hired a 14 year old. To all of you out there: NEVER HIRE A 14 YEAR OLD! I had these aspirations of taking him on under my wing and turning him into an orchardist…until I had to re-graft every single one of his trees…which was about 500 of them. Really, if you are going to hire a 14 year old, you have to watch their every move and don’t trust that they understand anything. I wasn’t able to do this because I needed to graft alongside him (you know, to get more done).

A month passed and I hadn’t finished grafting. My fingers and wrists ached, all my clothes were covered in grafting sealer, and my loathing of the activity soared to new heights. This was compounded with the death of my 3 month-old puppy (FedEx ran her over while I was on my way out to the grafting shed) and I was absolutely miserable with 1500 trees to go.

I shared my drama with an apple mentor and he suggested that I stop grafting, plant the rootstocks, and do some bud grafting in the summer. Of course! There was a way out! Budding 1500 trees this summer is doable (I think). If it’s not- I’ve located a professional bud grafter who will come and do all of my trees for me. Yesssssss.

Lesson learned: Discovering (through experience) how long a task will actually take you is called “Wisdom.”

Lesson #2: No matter how passionate you are about an activity, you can burn out. I didn’t think it was possible….

Lesson #3: Teach a bunch of friends how to graft well before the time comes for you to actually start grafting your trees. Have them practice over and over again. Then, hire them. Make sure your friends are over the age of 14.