How to Graft Oak Trees

What is the graft of a tree? The word "grafting" refers to a horticultural technique that combines parts from at least two plants to create a new, healthy specimen. The upper part (scion) grows onto the root system (rootstock) of another. It is done to propagate (breed) trees and can use the same or different species. Grafting is also used for plants.

Grafting branches on trees is a common practice for fruit tree growers and is used to influence factors like the color and flavor of the resulting fruit. A grafted tree is basically the result of the rootstock and scion; you can loosely compare it to two parents producing a baby. The rootstock forms the roots and controls how tall it will be, while the scion forms the other features.

Oak trees (Quercus spp., USDA plant hardiness zones 3-9) are not a type of tree that's often grafted, but in areas where their survival is threatened (like parts of California), it has been done on certain species. Only blue oak (Quercus douglasii, zones 8-11) could be successfully grafted.

The Tennessee Valley Authority also conducted a hardwood forest tree improvement program that experimentally grafted northern red oak (Quercus rubra, zones 4-8), chestnut oak (Quercus michauxii, zones 5-9) and white oak (Quercus alba, zones 3-9) trees. This study showed that northern red, white and chestnut oak could be grafted, with success rates ranging from 50 to 61 percent.

Always wear gloves when grafting because oils and contaminants on your hands could ruin the chances of a successful bonding. When ready to graft an oak tree, choose a rootstock that is at least two years old. One- or two-year-old wood is best for scions, and the portion should have at least two good buds. You should put these into a plastic bag, add damp sphagnum moss and store the scions in a refrigerator. The whip grafting method is the most practical; you can cut the rootstock oak back to 4 or 5 inches from the ground but only after the flow of sap has stopped for the season.

You can join the rootstock and scion with a rubber strip, and then you can paint both parts with grafting wax. You can remove the strip after four to six weeks; you should check it during that time, and if you find any excessive sprouts, you'll want to remove them. With large rootstocks, make a 1 to 1 1/2-inch diagonal cut on one side. Make two similar ones on the scion's opposite sides and insert them into the stock. Secure in the same way and paint with the grafting wax.

For fruit tree grafting, clip a branch from the rootstock with shears; it should be clean with no tears. Make a straight, long and sloping cut about 2 to 3 inches long and then cut the first inch of the top and bottom of your scion wood. These cuts should be on angles and should match the cut on the rootstock. Match up both cut surfaces, keeping the healthy green wood layers together.

Make a tongue cut on the rootstock. Start one-third of the distance from the initial cut's tip. Press your knife in a slow, downward rocking motion; the flap you create will meet with a similar cut that you can then make on your scion.

Adjust the scion until the gap between the two tongues opens. Line up the cuts and slide until they are interlocked, with the green wood of both pieces in contact. Use grafting tape or electrical tape to seal things up but don't make it too tight.