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the dwarf tree challenge

Posted by Michael Phillips 
the dwarf tree challenge
March 24, 2013 07:40PM
Legitimate organic debate about the economics of dwarf high density versus traditional freestanding trees is different from that of the IPM realm. The drivers in that system are not just small tree size but the seemingly low cost of herbicides and soluble chemical fertilization to prime such plantings. I say "seemingly" as this makes for trees lacking important soil allies and thus less able to stand up to disease. This requires stronger and stronger medicines to compensate ... which isn't necessarily an issue ... until pathogens develop full resistance.

Yet when we start thinking biologically -- clearly recognizing that less disturbance leads to fungal ascendancy and thus healthier trees -- possibilities may indeed open up. Here I want to issue a challenge to organic dwarf tree proponents to describe a workable system for holistic high density. Now there's a term. Achieving the understory requisites of runted root systems while at the same time lessening roughshod compromise with soil biology is not straightforward. What does a health-centered high density planting look like? What actions and cued to what timing? And how does the labor effort behind this stack up year after year when compared to freestanding trees in a more meadow-like ecosystem? Here I speak of a certain scale as well, say an acre and up. Finding biological equilibrium in a garden setting with a dozen Bud.9 trees is indeed doable. Take this to commercial scale and everything changes.

Lost Nation Orchard
Zone 4b in New Hampshire



Edited 3 time(s). Last edit at 03/25/2013 07:03PM by Michael Phillips.
Re: the dwarf tree challenge
March 25, 2013 10:44PM
I guess it depends on what you mean by 'high density'. My first thought is of M9 and Bud9 type trees. These are garden trees, they would need to be kept fairly weed free to thrive. Compost, wood chips would be good. I have 10 trees of Bud9, which get some composted horse manure in spring, the grass clippings blown into the rows from the lawn mower, and (you know I'm not strictly organic) occasional passes with roundup to knock back grasses in the row. Were I to go organic, I'd need to go heavier to wood chips, and work on finding some replacement burn-back material for the roundup. For my 10 trees, I could easily hand-weed. But that size tree would not scale up well in acreage without some herbicide help (I don't think it would need the nuclear wasteland herbicide strip generally used, but it's not going to shrug off witchgrass like more vigorous rootstocks).

Back at the orchard, I was very, very happy with M26 (clay soil, but with tile drainage at 40' spacing). These were trees that could be picked completely from the ground, filled in their space within the rows at 9 X 16', single post at each tree. The first three years I kept a 3 X 3' square rounduped, then let the ground cover have its way. The M26 had enough native vigor to easily tolerate the competition. I had a flail mower with a swing-arm attachment that mowed between the trees within the row, swinging out around the trunk of the trees. I maintained floor diversity by only mowing every other row, not coming back to mow the alternate rows until the ground cover started to regrow in the first rows.

So what would I do if I were to go back into the fray? I'm going to assume the soil I am familiar with (Vegennes clay, which despite its bad rep is fertile and holds a lot of moisture to get the trees through summer drought). I'd stick to the same size tree, be it M26, maybe Ottawa3, might even consider an Antonovka/Bud9 interstem. Personally, I would re-equip to mow between the trees within the row again, maintaining the ground as a mown meadow, but this size tree should tolerate any compost/wood chip/companion plant treatment you want to throw at it (having never thrown any of those treatments at these trees, take that with a grain of salt). Choice of rootstock might change depending on soil. I have seen erratic results with M26 in New York, from runted out to trees twice the size we had.

In short, I'd be looking for a tree vigorous enough to hold its own, but small enough to be easy to manage.

Possible dark horse: Comfrey. Michael has talked about it in the orchard at length, and I had watched a clump we had growing in the garden. The dense leaves smothered out all competition, then in fall collapsed completely. I have planted it under a couple of trellised plums (sometimes I crave challenge far too much), and have been very impressed with the degree of weed suppression for the last couple of years (I do comprehend the irony in calling a stand of comfrey under the trees 'weed suppression', but it has been keeping out the grasses, which are the most deleterious to tree growth). I had been pushing the comfrey over when it got too tall, thinking that the lawnmower would chop it up. That hasn't worked as well as I had hoped, so I guess I'll start taking a scythe to it this year to keep it more in check. Most of my Bud9 trees have reached the size I want them, and I'm tempted to plant the row with a comfrey ground cover. If that can substitute for herbicide for weed suppression... that would throw a different light on full-dwarf plantings. And if the test gets out of hand, I do have roundup, and I'm not afraid to use it.

Jim Gallott
New Haven, VT USDA Zone 5a
Re: the dwarf tree challenge
March 26, 2013 07:09AM
Hybrid understory management is indeed a good approach for trees on rootstocks in the 40% size class. Such trees on the likes of M.26, G.935, G.202, and interstems are managed to have a compact branch structure and be "freestanding" though often a permanent support stake is involved. And Jim is totally right about the pivotal factor involved here -- matching inherent soil fertility to the vigor of the root in order to get the right spacing in what's essentially a woodsy meadow ecosystem. I recommend this highly to those wanting smaller trees.

But it's the fruiting wall on trellis where the "organic challenge" truly comes into play. The more dwarfing roots like Bud.9 or M.9 (and it variants) and G.11 are trained more or less as high-reaching leaders with little permanent branch structure. Terms like "slender spindle" or "vertical axe" define pruning/pinching directives. That's the gauntlet that has been thrown ... how should the holistic grower manage the understory in this sort of high density planting?

Lost Nation Orchard
Zone 4b in New Hampshire
Re: the dwarf tree challenge
March 26, 2013 12:09PM
A sustainable dwarf system test seems like an exiting idea, meaning time money and environmentally sustainable. Since we all have different growing practices and philosophies, it would be a great way to sample the success of each. Our farm could contribute the following: 1. more detailed records of the existing and past plantings of dwarf trees in our low impact, uncultivated orchard. 2. Ongoing records of our two new plantings of high density trees on high vigor rootstocks. 3. Greenhouse planting of high vigor varieties. 4. Sample planting (onlgoing) of bud 9 interstem on standard. I can list all the details of management techniques and spacing. I would suggest some separate threads for real studies, and we should all perhaps talk about some scientific protocol if we want to get serious about this and other studies.
Re: the dwarf tree challenge
March 27, 2013 09:54PM
>>> But it's the fruiting wall on trellis where the "organic challenge" truly comes into play.

I guess my first question is 'Why?', as in why M9 class? If you are starting from scratch, the first question is what do I want from the orchard, not what does the orchard want from me. For me, no ladders is high on the list. A 40% tree does that and still leaves sufficient vigor to make the rest of the management easier. Does an M/Bud 9 get me anything extra in sufficient quantity to offset the additional management headaches? The Paradise rootstock was around for centuries as a garden plant, but only with the development of herbicide strips did it become practical as an orchard tree. I guess my answer is I don't particularly see where a full dwarf outside of a garden context makes my life any easier.

But, were I to try, this is what I would do:

My gut feeling is that any rootstock under a mown-meadow treatment is going to be smaller than under 'traditional' herbicide treatment, so I would start by thinking of the M9 more like an M27 when considering spacing (2.5-3 feet within the row makes sense, at least on chilly March evening sitting in front of the woodstove). I'd have mouseguards and a 2 foot wide band of woodchips down the row. At least the first 3 years, I would have to find some burn-back material to keep the chips at least modestly clear of weeds (this is a big assumption that I would be able to find something). Mow alternate row middles. Keep trees well fed foliarly w/fish and seaweed (I am very much a fan of stress-x powder to green up trees and get sweeter fruit). Gauge when to allow fruiting by when the tree is getting close to filling its space, which will be tough because it will start flowering well before it should. From there it would be a balancing act. The roots need a certain amount of tough love to force them out into the row middles, so the wood chip strip would be allowed to shrink as time went on. I would expect to need to be more on top of mowing than on larger established trees. Also I would expect more foliar feeding to keep trees sufficiently vigorous. Assuming my Vermont climate and clay soil, I'm not sure I'd put in irrigation, but first year they would need spot watering for first couple of months and any dry period. At the point where the trees were pretty much filled in, I would be needing to judge whether I could let the meadow gradually take over and use a swing arm mower or consider wood chips/burnback a permanent requirement. I would hopefully have judged the spacing correctly so that not much vigor is needed to maintain the tree and minimal/no ground cover suppression other than mowing would be needed. All this also assumes that I can keep borers, scab, lepidoptera and drought at bay. Minor details.

There, all solved, and I didn't even have to get up and put a log on the fire. I think the keys would be at least 3 years of minimal root competition to get their legs under them, controlling fruiting in the first years to prevent runting out, and lowering expectations of how much space each tree will be able to fill. I guess that is the one key: matching expectations of tree size to match the reality of what the rootstock can do under the management that can be provided. Now for the pesky detail of actually making it work.

Jim Gallott
New Haven, VT USDA Zone 5a
Re: the dwarf tree challenge
June 19, 2013 10:37AM
My mind spins with these considerations since most of our farm is now planted in B9 and we are only now attempting herbicide-free orcharding. B9 has been an amazing fit for our robust soil and disease laden climate. Also, we have been very happy with it's productivity. So is my only hope to slowly transition our farm away from B9 to be able to compete with whatever is growing on the orchard floor? (See my post about research on orchard floor management in this category.) And then there's this: how could a dwarfing rootstock like B9 ever be able to take up the amount of nutrients from the soil that a 70% or standard root system could? Has there been any good research done on comparing rootstocks for mineral uptake or do any of you have any observations? I'm thinking that in the long run, the only way you'll ever get a B9 to match the nutrient density you'll find in the fruit of a standard tree grown with holistic practices would be to dump huge amounts of mineral inputs into your orchard. What think?

Clair Kauffman
Zone 6b, Lancaster, Pennsylvania



Edited 1 time(s). Last edit at 06/19/2013 07:31PM by Michael Phillips.
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