How old/big to let stock get before field grafting?

I hope it makes sense to throw this out as one thread covering multiple species. I know a lot of the answers will vary a lot between species. In my own case, the species I wonder about when to field graft are pawpaws, persimmons, pecans, mulberries, Cornelian cherry, seedling apples, and jujube. It seems bench grafting usually requires fairly young stock, and potted trees are limited by pot size and other things, but for trees that are going to be field grafted it seems like it might sometimes be better and just as easy to let the rootstock get bigger/older before grafting, and those are the questions I’m interested in discussing.

For a little background, there are several reasons field grafting appeals to me. Persimmons and mulberries grow wild on my place, so generally all I have to do to have an established rootstock is to just avoid mowing the volunteers, and sometimes I already have a range of different sized volunteers to choose from in areas that I don’t mow. I generally want to postpone investing in trees that are small and fragile if I can take my losses first and make further investments later. Pawpaws and pecans seem potentially easier to grow in place from seed than to transplant. (I know the initial need for shade can complicate growing pawpaws in place from seed, but I have wooded areas I want to clear, so it seems easy to start them in the woods, then clear the woods to give them more sun.) With pawpaws and seedling apples and maybe Cornelian cherries I’m tempted to let the rootstock get big enough that I can graft above at least one lower scaffold branch in order to mainly have a known grafted tree but leave a small sample of the seedling fruit to try (or perhaps to wait even until I’ve gotten a taste of the seedling fruit before grafting at all.) With some species I’m inclined to wait until I can graft high enough that the graft itself will be out of easy reach of deer, etc. And with several species I simply want to graft onto the size/age rootstock that’s most likely to give me the best percentage of grafting success and survival, especially with species like persimmons where grafting is a bigger investment (especially if I include bagging to protect from psylla as part of the grafting process) and the need for more and more frequent after-care (particularly rubbing competing buds.)

So at what age/size would you prefer to graft the above species (or other comparable species), and why?

The only species on which I’ve really started to form opinions are pawpaws and persimmons. In my limited experience, I’ve had enough success grafting small potted trees, but I’ve had very poor success field grafting except onto larger more vigorous stock, so I’m inclined to wait until rootstocks are at least 5-6’ tall. Maybe I’m over-thinking all of this, i.e. maybe it’s best to let all rootstocks for field grafting get up to 5-6’ tall, but if so, then that’s my limited experience asking these questions. Of course, 5-6’ tall would translate to much younger wood for some species (e.g. mulberries) than others (e.g. pawpaws and, at least in my experience so far, pecans.)

Cousin

I wish I have access to your wild rootstocks. I like the 2" caliber rootstocks for bark graft. I headed it off around 4 feet tall and bark graft it. I found that I could get 95% take even on the hard to graft persimmon and almost 100% on paw paw. You need to wrap the union real tight with the electrical tape and wrap the whole scion with several layers of parafilm to prevent scion from drying out. The most important step is aftercare, you have to rub off all the new growth below the union every couple of days and sometime there is a shoot growing underneath the tape( if you don’t crush it or remove it then almost 100% failure).

Tony

I find bigger is always better, but sometimes small is all there is. So, it just depends on how desperate you are. I tried to graft some peaches last year to one-year stocks and they all failed - the stocks were too small.

Do you not worry at all about trees needing to heal over larger wounds? Pawpaws, in particular, seem to not heal over wounds so well, so I’ve been especially inclined to favor grafts that leave minimal exposed rootstock wood. I just don’t have much experience – largely because I’ve assumed it was better to avoid – cutting off stock where it’s 2"+ in diameter and placing my graft there.

Alternatively, I’ve been concerned about reduced vigor for the graft by grafting onto a smaller branch up in a larger tree. I think I remember Bill Reid on his pecan blog recommending cutting at least 1/3 or 1/2 of the rootstock off because the graft would have too little vigor to establish well otherwise. Do you follow any rules of thumb like that?

I’ve also been reluctant to leave larger rootstocks with nothing but a little scion for top growth, but I think I’ve had grafts on larger trees – I’m thinking particularly about mulberries right now – fail the tree just redirected its energy to the growth I left behind. Maybe I just missed the balance on how much nurse limb to leave. Or maybe I didn’t need to leave a nurse limb at all, even on a mulberry that might have been 4" at the base.

You’ve already got me questioning a bunch of my previous assumptions.

Of course, the other question is how soon to start growing the graft. Sometimes I have a choice of sizes to choose from in my rootstocks where that’s not an issue, but more often using bigger/older stock means waiting more years to graft and getting started later. I’m sure grafts on older, more vigorous stock catch up to some degree with grafts done earlier on smaller stock, but doesn’t grafting earlier generally put you a little closer to harvesting fruit from your graft, especially if the rootstock has already started to form scaffolds, etc. that are all cut away in the grafting process?

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Does that not make it harder for the new growth to push through the parafilm? Apparently it’s not an issue, but I’ve always been very careful to only have a single layer of parafilm over the buds (on the species for which I use parafilm) based on my assumption that parafilm could impede the new growth.

Cousin

The bigger the understock The better for bark graft imo. Once the scions took, they head toward the sky fast. Once I see the scions pushing buds with a big bulge I then unwrap the parafilm. You will be amaze to see how strong those buds are. They will push right through 2 layers of parafilm if I forgot to remove the parafilm.

Tony

Nope! It might look ugly but I’ve never had problems long-term. I have several 4" pawpaw trunks I topworked a few years ago and they are doing great now.

There is no reason to do that, cut it low instead and bark graft on the stump.

That seems counter-intuitive to me. You want all the root you can get with its stored up energy to push the scion.

I would say its easier to mess up by leaving too much nurse limb than to leave too little. It depends on the fruit - for persimmons I would never leave a nurse limb. I haven’t grafted mulberries so don’t know how they react.

If your stock is of decent size (1/2" or more) and you have nothing bigger, its best to graft it now rather than wait for it to get still bigger. All you want to avoid is grafting to stocks that are small enough that the graft may not take.

I think he’s suggesting cutting off most of the TOP of the rootstock, not the roots.

That makes more sense… I usually cut all of the top off :smile: The only reason to leave a top is when doing a bud graft.

Here are a couple things Bill Reid says on his blog. As best I can remember this is where I got my ideas.

“I was out in the field grafting more Kanza trees and came across a tree too large for a 3-flap graft but too small for a bark graft (photo at right). Sure, I could have placed a 3-flap graft up near the top of the tree. But, to make sure my graft will get a good push from the root system, I like to remove at least one-half of the top when choosing a spot to graft.”

“To ensure that there will be plenty of tree energy directed to pushing the graft, I like to place the graft union no higher than half way up the stock tree.”

Thanks, everyone, for helping me see so many of my false assumptions.

When you topwork a 4" tree, are you separately grafting the relatively smaller branches of a tree that is 4" in diameter at the base? Or are you cutting it off where it’s 4" in diameter (i.e. cutting the tree off below all the branches) and placing your graft there? Does this almost always mean a bark graft? Are there other types of grafts you find especially useful when placing scions on a large diameter stump?

Do you mean that the rootstock would be 2" in diameter 4 feet up? Or do you mean that the rootstock would be 2" in diameter at the ground but you place your graft 4 feet up where the diameter of the stock is much smaller than 2". In other words, what’s the diameter of the stock where it gets cut off for you to place your graft? It seems persimmons, for example, are often a lot smaller diameter 4’ up.

I have a few reasons (perhaps based on misguided thinking) for preferring to graft 4-6’ off the ground when field grafting. A lot of my field grafting (by which I mean simply grafting onto rootstocks that were planted or seeded or had volunteered long before grafting) is onto rootstocks in or around my pastures or crop fields. These are often spots where I’m never practically going to be able to water, and I can’t see any reasonable way to keep the grass down that I’d want to employ (beyond bush hogging a couple times per year and grazing my animals), and they’re going to be relatively more exposed to deer browsing on them, bucks rubbing their antlers on them, maybe even one of my own animals getting to them (getting out of the fence), etc. So grafts just seem a lot safer around 5’ off the ground, and that at least puts them above the grass and weeds. Some of these trees I’d like to eventually use for shade trees for my animals, so I’m commonly planning to prune any lower branches off anyway (e.g. mulberries, black walnuts, pecans…) And with others I’m pruning off lower branches simply because I figure the deer are going to eat everything they can reach, so there’s no point in trying to grow any fruit below 5 or 6’ anyway (or I’m wanting to be able to baffle them against squirrels…)

I’ve also heard that cold injury to Asian persimmons might be slightly reduced when grafts are placed higher on the rootstock.

Cousin

This photo of my 4 yrs old 2 " diameter native American persimmon rootstock. I topped it off at 4 feet height and bark grafted Jerry Lehman U-20A super large fruits for a D.Virginiana. you can see it has a nice looking tree form and vigorous growth to 4 feet above the union in 2 yrs.

Tony

Here I did the same bark graft with the Prok persimmon.

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Tony’s pictures say it all: lop it all off at 3-5’ and bark graft all your scions around it. This will heal well; do it more like 5’ if there are deer issues and 3’ if not. If the tree is branching by 5’ to say three scaffolds, cut at that point and put some bark grafts on each scaffold. If its small with small scaffolds at the height you need to graft at, put wedge grafts on.

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