Inlay Bark Grafting

A number of considerations must be addressed before attempting grafting; the grafting (scion) wood, the rootstock and the grafting method.

The scion wood must be collected while it is fully dormant. Mid March is a good time. The scion branches should contain buds from the previous seasons growth. With the walnut family, the buds to be used should resemble miniature cabbages. Those that resemble closed pine cones are male flower buds and will not produce new growth. The branches collected should be healthy, round wood with a small pith (centre of the stem is hollow in walnut family). The buds closest to the second year wood are the most mature and usually the best. Wax the ends by dipping them in melted candle or paraffin wax, wrap the sticks in a slightly moist towel and store in a sealed plastic bag in a refrigerator. It must be kept dormant until spring when the rootstock is ready for grafting and weather conditions are right.

The rootstock must be a related species to the scion used in the grafting. Black walnut is a common wild tree in Southern Ontario and makes a suitable rootstock for all of the Juglans species. This includes heartnut, butternut and Persian walnut. Same species rootstocks can also be used. Turkish tree hazel is a good rootstock for all of the hazels, mainly because it is non suckering. Chestnut is one of the easiest to graft of the nut tree species but also one of the most difficult to match for compatibility. American chestnut and Chinese chestnut are the same type and will inter-graft fairly easily, while European and Japanese chestnut will often fail when grafted to Chinese or American. The best success occurs when the rootstocks are the seedlings of the scion tree being grafted.

When the rootstock is beginning to burst buds, about 10-15 of May, it is time to start grafting. Trees can be top-worked, 2 to 3 metres up. Walnut trees graft better when it is done higher. Walnuts tend to "bleed" sap in the late winter and well into spring. This bleeding will prevent any grafting success. To stop this bleeding, it is best to cut the tree off 5 cm or more above the point where the grafts will be placed. Do this a week to ten days before attempting the graft. The shock of losing the top slows the development in the tree down and the bleeding stops. Cut the stock off again a few centimetres lower and watch for sap oozing out. If it has stopped, you may begin grafting. This process is not necessary with hickory or pecan because the sap pressure is much less. However, the graft should be made high enough in the tree that sap flow is avoided. Chestnuts and hazelnuts seldom bleed ,so they can be cut off and immediately grafted.

There are a number of grafting and budding techniques that work with nut trees. The one graft that works well with all nut trees is the inlay bark graft and that is the technique that will be described here.

1. The stock should be at least double the thickness of the scion for this method to work. The stock is prepared by cutting the branch to be grafted off squarely.
2. Make a vertical cut about 5 cm (2 inches) long, ending at the surface of your first cut, through the bark until resistance is felt at the sapwood.
3. Prepare you scion which can be 10-15 cm (4-6 inches) long, by deeply cutting away the wood on one side of the scion about 6 cm or 2½ inches from the bottom end of the scion stick. Turn over the stick and lightly shave the bark away on the backside of the previous cut. Finally make a chisel cut on the tip of the scion. Make sure you have 2-3 good shoot buds on the scion.
4. From the cut surface of the stock, gently lift the bark one side on the vertical cut made earlier. Slip the flat cut surface of the scion under this lifted bark, sliding it vertically between the bark and the sapwood, flat surface facing inward.
5. Hammer 2 nails ½ to inches long through the bark, scion and sap wood to hold the scion firmly in place. A third nail may be needed to close the gap in the bark beside the scion.
6. Cover all cut surfaces with a grafting wax. If this is not available, seal the top of the scion with carpenter's glue and cover all cut surfaces including the scion with aluminum foil. Leave a small flap as an opening for the buds to shoot out. Cover all of this with a clear plastic bag and close with a twist tie.
7. Optional: Firmly tie a stick or small branch, higher and beside, the graft as a perch for birds, so they don't use the scion as a perch and destroy the graft.

Follow up - As the graft begins to grow and green shows through the aluminum flap, cut an opening in the top of the plastic bag to allow the new growth room to expand. When the graft is well grown, you may remove the plastic bag and finally the aluminum. As soon as the graft is a foot or more out, support it with a brace tied to the branch or trunk.