Techniques of Grafting

• factors influencing graft union success:

  • compatibility
  • plant species
  • type of graft
  • environmental conditions
  • growth stage
  • virus
  • polarity
  • craftsmanship of grafting
  • plant growth regulators
  • post-graftage
• more distantly related plants = lower chances of compatibility
• "easy" species: stem anatomy and ability to produce callus
• Best callus formation is at cool temperatures
• Outdoor grafting is best during the spring
• Bark slips when cambium is active
• top grafting: the proximal end of the scion is attached to the distal end of the rootstock
• root grafting: the proximal end of the scion is joined to the proximal end of the rootstock
• Sometimes inverse polarity can be successful
• Reversed polarity can make permanently successful unions
• It's important to avoid wide angles/twisting of branches during grafting
• Make sure to align the cambial region
• symptoms of incompatibility:

  • failure to form a successful graft or bud union
  • yellowing of foliage
  • decline in vegetative growth
  • premature death
  • difference between scion and rootstock
  • suckering of rootstock
  • overgrowth near graft union
  • graft components breaking apart cleanly
• graft incompatibility: breakage at the graft union resulting from incompatibility
• What do you need for successful grafting?

  • compatible rootstock and scion
  • vascular cambium in close contact
  • proper physiological stage
  • protect from dessication
  • post-graft care
• effects of the rootstock on the scion:

  • size and growth habit
  • fruiting
  • size, quality, and maturity of fruit
  • cold hardiness
  • nitrogen use efficiency
  • edaphic conditions
  • disease/pest resistance
• effects of scion on rootstock: vigor and development
• effect of interstock on scion and rootstock:

  • dwarfing
  • stem strength
• mechanisms of rootstock and scion effects:

  • anatomical factors
  • nutritional and carbohydrate levels
  • absorption and translocation of nutrients and water
  • phytohormones, correlative effects, and gene expression
• grafting methods:

  • detached scion
  • approach
  • repair
• detached scion graftage: a section of the shoot of the scion is removed and grafted on top or side of rootstock
• approach graftage: the root system of the scion and shoot system of the rootstock are not removed until after successful graft union formation
• repair graft: used to repair or reinforce injured or weak trees
• types of detached scion graftage:

  • apical
  • side
  • bark
  • root
• apical graftage:

  • splice
  • whip-and-tongue
  • cleft
  • wedge
  • saddle
  • four flap
  • hole insertion
  • tip
• side graftage:

  • side stub
  • side tongue
  • side-veneer
  • side insertion
• bark graft:

  • bark
  • inlay bark
• root graftage:

  • whole-root
  • piece-root
  • nurse-root
• approach graftage:

  • spliced approach
  • tongue approach
  • inlay approach
• repair graft:

  • inarching
  • bridge
  • bracing
• detached scion graftage: most commonly used; scion is severed from its vascular connection
• splice graft: a simple slanting cut of the same length and angle is made on both the rootstock and scion; they are placed together and tied and wrapped
• Splice graft is commonly used for vegetable crops
• Splice graft is performed when the rootstock is dormant
• whip-and-tongue graft: scion is cut with a sharp grafting knife using a single motion; a second reverse cut is made 3/4 of the way into the first cut to form the tongue
• Whip-and-tongue grafts are typically done while dormant