Grafting involves joining two different plant parts so they grow as a single organism. For citrus, budding is the preferred form of grafting, using a single bud instead of a whole branch section. This process controls the mature tree size and ensures the resulting fruit is genetically identical to the desired parent tree, guaranteeing variety and quality. Using a specific rootstock, the bottom half of the graft, also provides the tree with resistance to certain soil-borne diseases and pests.
Preparing the Grafting Materials
Successfully grafting citrus requires selecting and preparing two components: the rootstock and the scion. The rootstock is the lower part of the new plant, providing the root system and influencing tree vigor and soil adaptability. A healthy rootstock, often a seedling, is chosen for its disease resistance and tolerance to specific soil conditions, such as high pH or poor drainage.
The scion wood, also called budwood, is the small section containing the bud from the desired fruit variety. This budwood must be collected from a disease-free, mature, and highly productive parent tree. Immediately remove all leaves from the scion wood after cutting to limit water loss and keep the wood cool and moist until use.
Grafting should be timed for when the plant’s vascular cambium is actively growing, which is when the bark “slips,” or separates easily from the underlying wood. This optimal period occurs during late spring through summer or in the fall, when daytime temperatures are consistently between 70°F and 85°F. Necessary tools include a sharp, sterilized budding knife and a material to secure the graft, such as specialized budding tape or grafting wax. Sterilizing the knife between cuts prevents the transmission of plant pathogens.
Executing the Citrus Budding Technique
The most common technique for citrus propagation is T-budding, used when the rootstock bark is actively slipping. The process begins on the rootstock stem, typically six inches above the ground, by making an incision that resembles an inverted letter “T.” This involves a vertical cut about one inch long, topped with a horizontal cut, made only deep enough to penetrate the bark. The knife is then used to carefully lift the corners of the bark on the T-cut, creating a small pocket or flap.
Next, harvest a single bud from the scion wood using a smooth, continuous cut that includes the bud and a thin, shield-shaped sliver of bark and wood. This bud shield should be handled using the leaf petiole, if present, to avoid contaminating the cut surfaces with oils or dirt. Use only a single, plump, dormant bud from hardened twigs, avoiding very young buds.
The prepared bud shield is gently slid downward into the pocket on the rootstock, ensuring the cambium layers of both parts align closely. The entire bud shield must sit neatly beneath the rootstock bark flaps, with the bud pointing upward. Once positioned, the entire area is tightly wrapped with grafting tape, starting below the bud and overlapping upward.
Tightly wrapping the union maintains firm contact between the rootstock and the bud shield, facilitating cambial layer fusion. The tape must cover all cuts entirely, but the bud itself must be left exposed to allow for future growth. This wrapping seals the union, preventing desiccation and protecting the area from pathogens while healing begins.
Ensuring Graft Success and Aftercare
Monitoring the grafted area for signs of successful union typically takes three to four weeks. A successful graft shows the bud remaining green and healthy, often beginning to swell slightly. Within ten to fifteen days, a successful union begins to form a hard, whitish tissue known as callus, where the two cambium layers are joining.
Once the bud appears healthy and the union is established, carefully remove the grafting tape to prevent girdling the rapidly growing rootstock. Leaving the wrap on too long can constrict sap flow and damage the union. Immediately following the graft, protect the new union from direct, intense sunlight, especially in warmer climates, to prevent tissue drying.
Consistent soil moisture is necessary throughout the healing process to support active growth without causing saturation. After the graft has firmly taken, immediately remove any new shoots, known as suckers, that sprout below the bud union. These suckers compete aggressively with the scion bud for resources. To encourage the bud to grow into the new tree canopy, the top of the rootstock is often cut back.