Tree propagation is a horticultural method used to create new trees from a parent plant. For plums, this process is generally vegetative, meaning it uses parts of the tree other than seeds. This is necessary because plum seeds rarely produce a tree with fruit identical to the parent. Propagating plums through techniques like grafting and budding is the most reliable way to maintain the specific characteristics of a high-quality cultivar. This clonal reproduction ensures the new tree will yield the same size, flavor, and disease resistance as the original.
Propagating Plums Through Grafting and Budding
Grafting and budding are precise techniques that join two separate plant parts, the scion and the rootstock, allowing them to fuse and grow as a single organism. The scion is a short segment of a young plum branch from the desired variety. The rootstock is the lower portion, typically chosen for its hardiness, disease resistance, or ability to control tree size. Success depends on aligning the cambium layers, which are the thin, actively growing tissues just beneath the bark of both the scion and the rootstock.
Grafting is most commonly performed during the dormant season in late winter or early spring before bud break occurs. The whip-and-tongue graft is highly effective for young rootstock and scion wood of similar diameter, creating a strong mechanical union. The cleft graft is another method, often used when the rootstock is significantly thicker than the scion, requiring the insertion of one or two scions into a wedge-shaped split. Once the cuts are made and the pieces are aligned, the union must be wrapped tightly with tape or rubber and sealed with grafting wax to prevent moisture loss.
Budding, such as T-budding or chip budding, uses only a single vegetative bud instead of an entire section of scion wood. This method is often done later in the season, typically from late summer through early fall, when the bark is “slipping” easily. The timing is crucial because the bark must be pliable enough to lift and insert the small bud shield into an incision on the rootstock. The wrapped bud remains dormant through the winter, and the rootstock is cut back the following spring to force the plum bud to begin growing.
Starting New Trees From Cuttings and Suckers
Hardwood Cuttings
Plum trees can be propagated from hardwood cuttings, which are sections of mature, dormant stems taken in late fall or winter. Cuttings are typically six to twelve inches long and are collected from the previous season’s growth. The basal end of the cutting is often treated with a rooting hormone to stimulate the formation of adventitious roots.
The prepared cuttings are then inserted into a well-draining, sterile medium like sand or perlite, with two-thirds of the cutting buried. For optimal rooting, the medium should be kept consistently moist and cool, often with the help of bottom heat to encourage root growth while keeping the upper buds dormant. The success rate for specific cultivars can be unpredictable compared to grafting.
Root Suckers
Suckers are shoots that emerge directly from the root system of a plum tree, often appearing some distance from the trunk. For grafted trees, these suckers are genetically identical to the rootstock, not the fruiting variety, and will produce rootstock fruit if allowed to grow. If the parent tree is on its own roots, the sucker will be a clone of the entire tree and can be transplanted to create a new one.
To propagate a sucker, it should be carefully dug up in early spring or late fall when the tree is dormant. The goal is to detach the sucker with a sufficient amount of its own root material attached, which ensures a higher rate of survival. After severing the connection to the parent plant’s root system, the new sapling is ready for immediate transplanting into a new location.
Caring for Newly Propagated Plum Stock
Immediate care for newly propagated plum stock, whether grafted, budded, or rooted from a cutting, centers on minimizing stress and promoting the healing of the union. For grafts and buds, the wrapping material must remain intact for several months to protect the cambium layers as they fuse together. Monitor the union for excessive constriction and remove the tape or rubber only after a strong, swollen callus has formed, usually by the following fall.
The young tree requires consistent moisture, especially during the first growing season, but the soil must be well-drained to prevent root rot. Watering should be deep and regular, but fertilization is generally avoided in the initial year to prevent burning the sensitive new roots and to encourage root establishment over top growth. Any shoots that emerge from the rootstock below the graft or bud union must be promptly removed to direct all the plant’s energy into the desired scion wood.
Protecting the tender new growth from environmental stressors is important for survival. Wind can easily snap the fragile graft union or young shoots, so a stake for support is often necessary. The tree should be protected from intense, direct sunlight initially, and a layer of mulch can help to conserve soil moisture and regulate temperature around the roots.