Commercial nurseries depend on hand grafting by skilled workers to perpetuate the hundreds of colourful cultivars of Japanese maple. Cuttings usually root poorly, and scions grafted to seedling rootstocks grow more vigorously. Home gardeners could avoid the high cost of nursery-grown trees by starting their own Acer palmatum rootstocks from seed and learning to graft their own Japanese maples. Many grafting techniques succeed, but amateurs should consider one of the simplest high-production methods—the side-veneer graft.
Store 1-year-old rootstock seedlings outdoors in the fall to harden off normally. Allow at least six weeks of winter chill before bringing the rootstock maples indoors for grafting. Let the rootstocks acclimate to the warmer temperatures for one week.
Cut dormant scion wood from 4 to 6 inches in length from the branches of the Japanese maple cultivars you wish to propagate. Each scion should hold three or four buds. Sterilise the scion by wetting with isopropyl alcohol. Store under refrigeration in a wrap of damp paper towels, sealed in a ziptop bag, until needed.
Slice a shallow diagonal cut 1-inch long on the side of the seedling maple's stem. Cut no deeper than one-third the diameter of the stem. Cut straight across the flap at the base and remove it from the stem.
Trim a scion to fit the exposed cut. Start the trim cut 1 1/4 inches from the scion's base. Slice diagonally through the scion, ending the cut 1/4 inch from the scion's base and shearing off the last 1/4 inch of damaged wood.
Fit the scion to the wound on the rootstock's stem. Cambium layers of both scion and host must meet in order to heal. Wrap the graft from the bottom up with grafting tape, covering all parts of the graft junction. Seal any gaps with grafting wax.
Allow six weeks for healing. Carefully slice away part of the grafting tape to check for healthy callus. Trim off the rootstock top 1/2 inch above the graft if properly healed.
Use a genuine grafting knife honed razor-sharp for the best results. Grafting knives differ from ordinary pocket knives in that the straight, single-bevelled cutting edge cuts clean and flat. The double-bevelled edge of a pocket knife wanders, creating a graft with gaps between scion and host.
Prepare all tools and materials in advance. Work quickly, because if the fresh cuts dry out before you finish the graft, the graft probably won't take.