A bonsai tree is not a specific species but the result of horticultural training, meaning any suitable tree can be propagated and cultivated using the bonsai method. The art form relies on standard plant propagation techniques to create the starting material for training. These techniques allow enthusiasts to produce new stock with desirable genetic traits or acquire a head start on trunk development. Propagation offers a direct path to acquiring pre-bonsai material.
Starting Bonsai Material from Cuttings and Seeds
Propagating from cuttings creates a genetic clone of the parent tree, ensuring the new material possesses the same desirable characteristics, such as foliage size or growth habits. The ideal time for taking cuttings is typically during late spring or early summer when the tree is actively growing, allowing for the use of softwood or semi-hardwood material. Cuttings should be taken just below a node, where rooting hormones naturally concentrate, and then dipped into a commercial rooting hormone to stimulate root development. The prepared cuttings are then inserted into a well-draining, soilless medium, such as a mix of perlite and peat moss, ensuring at least two leaf nodes are buried.
Growing from seed offers the advantage of producing a plant with a strong, natural root system, though this method is slower. Many temperate tree species have seeds that exhibit dormancy, requiring stratification to simulate the natural cold and wet conditions of winter. This often involves soaking the seeds for 24 to 48 hours, followed by placing them in a moist medium like peat moss in refrigeration for 30 to 120 days, depending on the species. Once dormancy is broken, the seeds are sown in a shallow seed tray, where the resulting seedlings benefit from genetic variation that can lead to unique specimens.
Advanced Propagation Using Air Layering
Air layering is a specialized propagation technique used in bonsai cultivation to quickly create a larger, more established trunk section. This method bypasses the years of growth required to thicken a trunk from a seedling or small cutting. The process begins in the spring and involves selecting a branch or trunk section with the desired shape and size. A ring of bark, approximately one to two times the branch diameter in width, is carefully removed down to the cambium layer, the thin tissue just beneath the bark.
Scraping the cambium layer interrupts the downward flow of carbohydrates, forcing the plant to develop new roots above the injury site. A rooting hormone is often applied to the exposed wood to encourage root formation before the area is wrapped with moist sphagnum moss. The moss is then encased in plastic wrap or foil to maintain high humidity and darkness, creating an ideal rooting environment. Within a few weeks to several months, new roots will form, allowing the rooted section to be separated from the parent tree as a new pre-bonsai.
Initial Training and Care for New Bonsai Stock
After successful propagation, the newly rooted material requires careful repotting and initial training to transition into a pre-bonsai state. The new plant should be potted into a deeper grow pot or training container to maximize growth. For seedlings, trimming the taproot promotes the development of a radial root system, known as nebari. Cuttings and air layers may also require initial root pruning to establish a flatter, more balanced root base.
Structural training begins after repotting to establish the desired movement and taper in the trunk. This is achieved using anodized aluminum or copper wires coiled around the trunk and primary branches. The wire gently bends the young, flexible wood into a curved or angled shape, setting the foundation for the tree’s future silhouette. Newly separated stock requires sheltered recovery in a semi-shaded area protected from harsh sun and strong winds. Consistent moisture is essential, and fertilizer should be withheld for the first few weeks following separation or repotting while the plant establishes its new root system.