Grafting Fruit Trees
Author Daniel Gasteiger
You’re looking at scions set in the split stump of a small branch that conveniently sprouted two seasons ago. This graft points into a space that could really use a low branch. Notice the leaf buds where the scions meet the stump. The most rapid growth occurs around leaf buds, so the design of the graft encourages the scion to grow into the stump.
It’s pruning and grafting time in my small kitchen garden, as it must be for nearly everyone in hardiness zone 6 and lower (north of zone 6). But time is running out. You should stop pruning when the leaf buds on your trees start to plump up in preparation to open, and that usually happens in early April.
My last five posts have been about grafting and pruning. I hope you’ve put the information to use. This post and the next one finish the series. This post presents my thinking about grafting onto an old established tree and the next post talks you through building a graft step-by-step. In my previous post, I described the equipment I use for grafting and introduced a video that takes you through the procedures I follow to graft red apple tree scions onto a green apple tree… so please read that one and watch the video if you want to get started immediately.
Harvesting Stock for Scions
You can harvest grafting stock all winter and store it until you’re ready to work. I harvest stock as I prune in late winter. When I can spend a half hour, I choose a problem to sort out in my red apple tree and take out a limb or two. Then I cut twelve-inch twigs off the ends of the small branches and put a bunch in a makeshift bucket.
If I have a lot of grafting to do, I focus on it almost exclusively until pruning season is drawing to a close. Then I stop grafting and make a mad dash through whatever pruning is left to do.
Graft onto Thin Branches
I like to graft onto very small branches—ones that are about a half inch in diameter. The technique, summarized, goes like this:
- Cut off the root branch and leave a stump.
- Split the stump across the middle, creating a one-to-three-inch crack.
- Whittle a scion and insert it on one end of the split.
- Whittle a second scion and insert it in the other end of the split.
- Wrap and waterproof the graft to protect it from the elements.
I’ve grafted into branches as wide as two inches across, but a branch that heavy requires one more tool than I usually carry (see box).
Graft to Larger Branches
The grafting technique I use is very easy to duplicate. Other methods require more precise cutting to align scions with root stock. There are special tools available that will cut the end of a scion and a socket on the root stock in which to insert the scion. Using such a tool, you can graft onto branches that are too large to split with a knife.
The technique I teach here works with any branch that you can split across the center with a knife. I’ve had luck with branches up to about 1.5 inches. The technique of cutting off the branch and then splitting it applies as well to these larger branches as to smaller ones. However, when you’re ready to insert scions, a utility knife is too flimsy to hold open the split on such a thick branch.
To deal with this problem, I put a flat-head screwdriver in my equipment bucket. To open the split, I work the tip of the screwdriver into the center of the branch—pointing straight into the split. I keep the screwdriver as far as I can from the bark ends of the opening, and use it as a lever to pry the branch open as I set scions in place (below).
When grafting into a thick branch—this one is about an inch across—I use a screwdriver to hold the split open as I place scions. Here, the scion isn’t all the way into the crack, but the bark aligns well with the bark of the stump. You can see that the scion will bulge out a little once it’s in position.
I cut a selected branch off square about two inches from where it attaches to the tree. I try to preserve the bark at the cut, so I use a fine-toothed saw for thicker branches, and sharp bypass pruners for thinner branches.
In an old, established tree, there may not be many conveniently-located small branches to receive grafts. This was the case with my ugly green apple tree. Knowing too little about grafting, I jumped in and started scions on large branches in poorly-chosen locations. I’d encourage you, instead, to prune your old problem trees for a season or two before you start grafting in them. Pruning encourages new growth, and in the second year, you’re likely to have many small, young candidate branches on which to graft stock from other trees.
Small Kitchen Garden Guidelines for Grafting
Here, in no particular order, are things I keep in mind as I work to convert my green apple tree into a red apple tree:
After three seasons, this graft is coming together nicely; it will probably produce fruit this season. It’s likely that this winter I’ll graft onto the branch that emerges just below the established graft.
Get the tree under control (if it’s not) by pruning according to the guidelines I presented in Prune Fruit Trees – 3: What and Why. If you’re dealing with a serious problem tree, you might put off grafting for a few seasons as you bring the tree around.
Prune before you graft. As you prune, you may need to climb your tree or at least stand on its branches. Worse, when you cut away old growth, it may fall through the branches. This activity could damage new grafts, so finish the season’s pruning on the host tree before you start grafting on it.
In a big, old tree, do lots of grafts. My grafting technique was poor when I started and I’d have about a 50% success rate. So, by doing 90 grafts in a season, I was confident I’d have 45 survivors. If you do ten grafts along a main branch and they all survive, crowding each other, you can prune some off in subsequent seasons.
Align bark. When I tell you that the bark on a scion must align with the bark in its host stump, I mean that the edges of the bark must align. The curve of the scion is tighter than that of the host stump, so the scion will bulge slightly out of the crack in which you set it.
Graft onto short stumps. Leave as little of the original wood as it practical; this reduces the chances of the host tree putting out competing branches that you’ll need to prune away later.
Graft to fill spaces. Especially on large, old trees, look for branches that come off the bottoms of larger branches, and graft onto those. Prune growth that comes off the tops of branches. This encourages the tree to develop a low profile and keep fruit within reach.
Graft to “repair” damaged branches. Sometimes, you’ll find damage on a branch you’d like to retain. Cutting the branch off behind the damage, and grafting into the shortened branch can save it while converting it to some other variety of growth.
Stay alert!Whatever knife you use for grafting needs to be extremely sharp. Don’t cut toward your body parts with it! Especially when you’re splitting a stump, don’t hold onto the stump or its parent branch. Sometimes the stump opens up and the knife slides through with little resistance. I did most of my grafting with only nine fingers one season because I got careless.