Japanese Maples (Acer palmatum) are highly valued ornamental trees prized for their delicate foliage and brilliant seasonal color changes. Cloning, or asexual propagation, creates an exact duplicate of a desirable Japanese Maple. This method produces a new plant genetically identical to the parent tree, ensuring all unique characteristics are preserved. Cloning is the standard practice used by nurseries and enthusiasts to maintain the integrity of specific cultivars.
Why Cloning is Necessary for Specific Varieties
Japanese Maples propagate naturally through seed (sexual reproduction), which involves genetic recombination. Seedlings inherit a mixture of traits, leading to genetic variation. For most named ornamental varieties, such as ‘Bloodgood’ or ‘Tamukeyama’, planting their seeds will not yield a tree with the same characteristics.
These seeds typically revert to the generic green-leafed form, often with a more vigorous growth habit. To replicate the delicate leaf shape, specific color, or weeping form of a sought-after variety, a piece of the parent plant must be physically used. This asexual method bypasses the unpredictable genetic lottery of seed starting, guaranteeing a true-to-type clone.
Propagation Through Grafting
Grafting is the most reliable and commercially preferred method for cloning Japanese Maples, combining a desired top section (scion) with a hardy root system. The scion is a small branch piece from the cultivar you wish to clone, typically joined onto a vigorous Acer palmatum seedling rootstock. Highest success rates occur during late winter or early spring.
Professional growers often use the splice graft or whip-and-tongue method, requiring a sharp, sterile grafting knife to make matching cuts. The goal is to perfectly align the cambium layers—the actively dividing cells just beneath the bark—of both pieces. This alignment allows the vascular systems to fuse, creating a single, functional tree.
The scion, collected while the parent tree is dormant, is secured tightly to the rootstock using specialized grafting tape or rubber bands. This wrapping holds the cambium layers in contact and prevents the wound from drying out. Grafting wax or sealant is often applied over the union to exclude air and moisture, protecting the tissue until the graft heals.
Propagation Through Stem Cuttings
Propagating Japanese Maples through stem cuttings is an alternative method, though it is generally more challenging and less successful than grafting. This technique forces a severed piece of stem to develop its own root system, resulting in a tree that grows on its own roots. The best time to take cuttings is in late spring or early summer when the new growth is soft (softwood) or semi-hardwood.
Cuttings should be 4 to 6 inches long, taken from the current season’s growth with a clean, angled cut just below a leaf node. All but the top one or two leaves are removed to reduce moisture loss. To encourage root formation, the base of the cutting is often lightly wounded by scraping a small strip of bark, then immediately dipped into a rooting hormone powder or liquid.
The prepared cuttings are inserted into a well-draining rooting medium, such as perlite and peat moss or coarse sand. The medium must be kept consistently moist to promote root development. Although simpler than grafting, many desirable Japanese Maple varieties resist rooting, contributing to this method’s lower success rate for commercial production.
Essential Aftercare for Cloned Plants
Once propagation is complete, the newly cloned plant requires a controlled environment for survival. High humidity levels are necessary to prevent desiccation while vascular systems fuse or new roots form. This is often achieved using a mist system, a closed propagation chamber, or a humidity dome.
The young plants must be protected from direct, intense sunlight, which can scorch the tender foliage. Bright, indirect light or dappled shade is ideal during this initial healing phase. For grafted plants, the union must be monitored, and any growth emerging from the rootstock below the graft must be promptly removed to prevent it from outcompeting the scion.
As new growth hardens off and the union or root system becomes robust, the plant must be gradually acclimated to normal outdoor conditions (hardening off). This transition involves slowly reducing humidity and increasing light exposure over several weeks. Once hardened, the new tree can be potted up or transplanted, ready to begin its life as a genetic replica of the parent cultivar.