“Side grafts” are grafts in which the scion is inserted into the side of the rootstock's branch by one method or another. You can use them on sapling trees a few years old to turn them from one kind of tree into another, such as to create a weeping form.
Why You Might Use a Side Graft
Like all grafting, side grafts are a more common practice in the horticultural industry of creating plants for sale. The side graft lets growers join a new variety of plant onto a middle-aged rootstock, such as a young tree.
For the (rather adventurous) home gardener, the appeal of the side graft is that it can be used to “replace” trees already planted in the field. The side graft can work on the size that most trees are planted at: 1.5 to 2-inch caliper. By side-grafting at the top of the tree, you could change a tree, or perhaps a whole allee of trees, into a new form, such as a weeping standard.
In general, side grafts are used to connect a scion to a same-size or slightly larger rootstock that is probably a few years old. The rootstock is old enough to have some stiffness and thickness to it, but not thick enough to make a cleft graft and without enough bark for a good bark graft.
The typical size for your rootstock is one inch thick. The scion can be much smaller, down to the typical “pencil-thick” guideline.
What You Will Need
- Winter: all wood should be dormant.
- A grafting knife, to cut scion wood.
- A thin-bladed chisel (preferably) or a sharp butcher’s knife
- A mallet
- Rootstock: a tree of about 1” caliper at the site you will graft
- Scion: one cutting per rootstock, much thinner than the rootstock
- Plastic tape or string and sealing wax
Making the Side-Stub Graft
- On a healthy dormant tree, choose a site with wood about one inch thick. A major branch can make a side good graft, but to replace the whole top of the tree you’ll want to work on a part of the trunk. To create a weeping tree, you’ll want a site high on the trunk, typically at least seven feet.
- Prepare your scion by creating a 1” long wedge at its bottom. Two cuts with a sharp grafting knife make the two long, straight (not wavy) faces of the wedge.
- Create a cleft in the rootstock by placing your chisel at a 20 to 30-degree angle from the trunk or branch and, using your mallet, driving it in one inch deep. With a good cut, bending the branch opens the cleft, but the branch is still so strong that when let go it shuts tightly.
- Insert the scion. Bend the branch back gently to open the cleft. Insert the wedge of the scion all the way into the cleft, matching the flat sides for maximal contact between rootstock and scion, and then let the branch go.
- Seal the graft by wrapping it tightly top-to-bottom with a twine. Pour sealing wax or apply Parafilm tape over the wrapped union.
- Follow up with general aftercare. In spring when the scion begins to grow strongly, cut off all the rootstock growth above the graft. Make your cut as close above the graft as you can without disturbing the graft, angling the cut away from the scion so as to direct and drain rain away from it.