Plant propagation is the process of creating new plants from various sources, a foundational practice in horticulture. This process increases plant numbers and preserves desirable characteristics from a parent plant. The mulberry tree, belonging to the genus Morus, is a rewarding species for the home gardener because it can be successfully propagated using several distinct methods. The choice of technique depends on the desired outcome and the time of year, whether seeking a genetic clone or simply growing a new tree.
Starting New Trees From Cuttings
Propagating mulberry from cuttings is the most reliable method for creating a genetically identical clone, ensuring the new tree produces the same fruit quality. This technique uses two types of material: dormant hardwood and actively growing softwood.
Hardwood cuttings are collected during late fall or winter when the tree is dormant. These sections should be 8 to 12 inches long and pencil-thick, cut just below a node. After dipping the base in rooting hormone, plant the cuttings into a well-draining medium, burying about three-quarters of their length. Using a heat mat set between 70 and 80 degrees Fahrenheit can increase rooting success.
Softwood cuttings are taken during late spring or early summer, using fresh, flexible green stems while the tree is actively growing. These are shorter, usually 6 to 8 inches long. Remove all but the top one or two leaves before dipping the cut end in rooting hormone powder.
Insert the piece into a sterile, porous rooting mix, such as peat moss and perlite. Maintaining high humidity is necessary, often achieved by placing a clear plastic dome over the pot to create a mini-greenhouse environment. Roots can begin to form within a few weeks, but the cuttings must remain protected until they are well-established.
Growing Mulberry Trees From Seed
Using seeds produces a large number of new trees but introduces genetic variation; the resulting tree may not resemble the parent, especially regarding fruit quality. Seedlings typically require five to ten years to reach maturity before fruiting. Start by harvesting seeds from ripe fruit and cleaning them thoroughly of all pulp to prevent fungal growth.
Mulberry seeds require cold, moist stratification to mimic winter conditions before they can germinate reliably. Mix the cleaned seeds with a slightly moist substrate, like sand or peat moss, place them in a sealed plastic bag, and refrigerate for 60 to 90 days.
Following stratification, sow the seeds indoors in small containers during late winter or early spring. Cover the seeds with about a quarter-inch of soil and keep them consistently moist. Gentle warmth can encourage germination, which typically occurs within two to six weeks.
Specialized Techniques: Grafting and Air Layering
Gardeners use specialized asexual methods to quickly reproduce a specific, named cultivar, such as a weeping or sweet variety. Grafting involves joining a small piece of the desired cultivar (the scion) onto the root system of a different tree (the rootstock). Using the scion’s mature wood bypasses the juvenile phase, allowing the new tree to flower and fruit faster, often within the first or second year.
Air layering is an advanced technique that produces a larger, more established plant faster than standard cuttings. This process induces root formation on a branch while it is still attached to the parent tree. A section of bark is removed from the branch, and the wounded area is encased in a moist rooting medium, like sphagnum moss, and wrapped tightly in plastic to maintain humidity.
Establishing Young Trees
Once new roots have formed, the young plant requires careful management to ensure survival. Plants rooted in high-humidity environments, such as under a dome, must undergo a gradual process called hardening off. This involves slowly acclimating the young tree to the harsher, drier outdoor conditions over seven to ten days.
Hardening off prevents transplant shock by gradually exposing the plant to increasing periods of direct sunlight, wind, and lower humidity. After this transition, the mulberry tree can be moved to a larger pot or its permanent location. The ideal time for transplanting is late spring to mid-summer, benefiting from warm soil temperatures for root growth.
For seedlings, it is recommended to grow them in a nursery bed or large container for two to three years until they reach 12 to 18 inches. Post-transplant care should focus on consistent watering during the first year to support the developing root system. Initial pruning can also be performed to begin shaping the tree.