DIY interstem grafting

I was wondering about the process to create an interstem-grafted tree: usually one where a piece of dwarfing rootstock is grafted between a larger rootstock and the scion. We have several versions that I bought commercially going like gangbusters in our orchard. I found this helpful article which describes doing both grafts in the same year, which would be a real time saver if you could get both grafts to take.

More on why I am interested: our biggest issues are anchorage in high winds and alkaline soil. Most dwarfing rootstocks handle those conditions poorly. If I can get a dwarfing intermediate on my preferred MM106 rootstock, I can put trees in places that won't fit a larger tree, or trial new-to-us varieties faster.

I've done quite a few of these with 6-12" interstems. I would say my success rate for the double graft is about 50%. Most of those failed still have the interstem succeed to use later.

The way I went about it the first year is to order full and interstems rootstocks at the same time -- for me P18 and M111 rootstocks (for wet soils) and M27 interstems. After I cut the M27 interstems, I just grafted those also to get some pure dwarf trees.
The next years, I can just re-graft the failures and take new interstem wood off of the M27 failures when collecting scion wood in winter.

My trees are 3 years old, so i don't have enough growth to evaluate how tall they will b, but the trees have good health and strong grafts... I got rootstock by the 100's so the cost was low and quantity plenty for my needs..

The trick to getting a high success rate when doing double interstem grafting is to match up the cambium layers as close as possible for each graft.
This means it will take far less time for the graft to heal and it also helps the sicon gain moisture far faster than other styles of grafting.
For easiest success use a fair sized dwarf sicon and then use bud grafting for the desired fruit. If you should want to be able to start more than one variety on the same tree, this will allow that.
Other wise use a size matched sicon for the second graft. Tape both well and try to leave them alone, only watering when needed.

Most of the grafts I've seen fail when done this way are because of folks wanting to "take a peak" at the graft to soon.
Give your grafts time to at least start the healing process before checking the actual graft, a look at the sicon leaves will tell you if you did a good job or not in the mean time.
I give grafts one full month before I check by removing the graft banding, prior to that I usually see signs of the wound bulging a bit under the banding, which means the graft took and is callusing well.

This may be of help to you grafting fruit trees

Where do you buy the dwarf interstem scions?

@ Ken: I'm pretty sure you don't. You buy bulk bareroot dwarfing rootstock and cut the scion off of them.

As an aside, is all this franken-tree stuff really necessary? If you need larger roots why not just go with that, and then train the tree not to outgrow its space.

Alternatively, presumably the small spaces are going to be in zone 1 or 2, go ahead and summer prune every year and feed the prunings to rabbits or sheep or something. The stripped branches make great Rocket Stove/Heater fuel or can be used for mulch.

Kyrt Ryder wrote:I'm pretty sure you don't. You buy bulk bareroot dwarfing rootstock and cut the scion off of them.

Correct

Kyrt Ryder wrote:
As an aside, is all this franken-tree stuff really necessary? If you need larger roots why not just go with that, and then train the tree not to outgrow its space.

Alternatively, presumably the small spaces are going to be in zone 1 or 2, go ahead and summer prune every year and feed the prunings to rabbits or sheep or something.

Nothing is necessary, but it is a useful tool to have in the tool-kit. First, I don't want to fight the vigor of a tree for its lifetime if I can get the rootstock to do that for me. I have 500 trees and the idea of summer pruning is costly, either in my time or paid labor. Those costs would drive up my cost-of-goods-sold. Second, dwarfing trees have the virtue of precociousness as well as small size. That may be even more valuable in situations like mine, where we are trialing over 75 varieties now. The sooner I can get data, the sooner I can graft over the rootstocks in the ground to something that will work. One thing we've done is interplant dwarfs and semi-dwarfs, with the intention of removing the dwarfs once the semi-s fill in, but I have an income source much sooner. And let's not forget that my alkaline soil will tolerate only certain rootstocks, but I can add some disease resistance on the interstem.

So IMHO, it really depends on the goals whether this is a useful technique for you.