Grafting

1. Grafting • Defn: connecting 2 pieces of plant tissue to grow as one plant • Terms: • scion: upper portion (usu. the shoot system) • stock: lower portion (usu. the root system) • interstock: stem piece between the scion and stock • budding: scion is reduced to a bud

2. Reasons for grafting/budding • perpetuating clones that can’t be maintained by other asexual methods • obtaining the benefits of a rootstock • changing cultivars of established plants (usu. fruit trees) • obtaining special plant forms • repairing damaged parts of trees • virus indexing

3. Growth activity of stock/scion wood • for some methods, best results are obtained when both stock and scion are dormant • for other methods, stock and/or scion wood needs to have “slipping” bark

4. Grafting Methods • Bench grafting • Field methods • Container or field methods • Repair grafting

5. Bench grafting • Whip-and-tongue graft • Saddle graft

6. Whip-and-tongue grafting • useful for small (1/4-1/2 in.) material, double working (interstocks), root grafting, and bench grafting • splice grafting (the tongue is not made) • both stock and scion are dormant

11. Saddle grafting • useful for machine grafting, bench grafting of grape and Rhododendron • scion and stock should be the same size • grafting is done when stock and scion are dormant, then the completed graft is stored in a grafting case until the graft union has healed

13. Field methods • Cleft graft • Wedge graft • Bark graft • Four-flap graft

14. Cleft grafting • useful for topworking fruit trees, crown-grafting grapes • the best time is early spring, before active growth • wedge grafting allows 1 more scion per stock

17. Formation of successful graft unions: sequence of events • lining up of vascular cambia • the wound healing response • callus bridge formation • new cambium formation • vascular tissue formation

18. Bark grafting • Two types (rind and inlay-bark grafts) differ only in prep of stock’s bark, which should be slipping • often used in lieu of cleft graft later in the season

20. Container or field methods • Side grafts • Approach grafts

21. Side grafting • defn: (smaller) scion inserted into the side of a (larger) stock • Types • side-stub: nursery trees too large for whip-and-tongue, not large enough for cleft • side-tongue: useful for broad- and narrow-leaved evergreens (e.g., oriental arbovitae) • side-veneer: useful for small potted plants, e.g., upright junipers

24. Approach grafting • two independent plants are grafted together • after union, the top of the stock and the base of the scion are removed • used when other methods are unsuccessful (e.g., Camellia) • often done on plants in containers • three methods: spliced-, tongued-, and inlay-approach grafting

26. Repair grafting • Inarching • Bridge grafting

27. Inarching • used for repairing damaged roots of a full-grown tree • seedlings are planted around the tree during the dormant season, grafting is done in the spring

29. Bridge grafting • used for repairing a damaged trunk • early spring (with the bark slipping) is the best time • (dormant) scion wood should be 1/4 to 1/2 in. diam.