Plant Grafting: A Horticultural Technique
Plant grafting is a horticultural technique where parts from two or more plants are joined so as to appear to grow as a single plant. In grafting, one plant, the scion, is selected for its flowers, fruits, or other desirable characteristics. The other plant, the rootstock, is selected for its roots, which should be strong and healthy or tolerant of particular soil conditions. When properly executed, the vascular tissues of the two plants will join together, creating a union.
Components of a Graft
- Scion: The upper part of the graft, comprising shoots, buds, or a stem cutting, that will develop into the desired plant characteristics.
- Rootstock (or Stock): The lower part of the graft, providing the root system. It is selected for its vigor, disease resistance, soil adaptability, or dwarfing effect.
- Graft Union: The point where the scion and rootstock are joined, requiring proper alignment and contact of cambium layers for successful fusion.
Types of Grafting Techniques
- Bud Grafting (Budding): A single bud is used as the scion. Includes T-budding and chip budding.
- Whip and Tongue Grafting: A long, sloping cut is made on both the scion and rootstock, with interlocking "tongues" for increased contact.
- Cleft Grafting: The rootstock is cleft (split), and the scion (usually a small twig) is inserted into the split.
- Bark Grafting: The scion is inserted under the bark of the rootstock.
- Approach Grafting (Inarching): Two independent plants are grafted together while both are still rooted. After the union is successful, one is cut above the graft, and the other is cut below.
Reasons for Performing Grafting
- Propagation of Clones: Grafting is often used to propagate plants that do not root easily from cuttings or other methods.
- Disease Resistance: A disease-resistant rootstock can be combined with a scion that produces desirable fruit or flowers.
- Dwarfing: Certain rootstocks can dwarf the size of the scion, making it easier to manage and harvest fruit.
- Faster Fruiting: Grafting can sometimes result in earlier fruit production compared to growing plants from seed.
- Repairing Damaged Trees: Bridge grafting and inarching can be used to bypass damaged sections of a tree trunk.
- Changing Cultivars: A new cultivar can be top-worked onto an existing tree by grafting.
Factors Affecting Graft Success
- Compatibility: The scion and rootstock must be compatible. Generally, this means they should be from the same or closely related species.
- Cambial Alignment: The vascular cambium (a layer of actively dividing cells) of the scion and rootstock must be in close contact for proper fusion.
- Timing: Grafting is typically done during the dormant season or early spring when the plants are actively growing.
- Technique: Proper cutting, alignment, and securing of the graft are essential.
- Environmental Conditions: Temperature, humidity, and protection from pests and diseases play a role in graft success.