Grafting

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Grafting Budding Theory
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Reasons for Grafting

• Unable to propagate from cuttings
• Benefits of certain rootstocks
• Disease resistant
• Dwarfing or vigor
• Changing cultivars of established plants
• Old cultivar not in demand (topworking)
• For pollination
• Variety of fruits on one tree

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Reasons for Grafting

• Hastening growth of seedling selections
• Quicker to bearing stage
• New varieties that are not vigorous on their own
• To obtain specific forms of growth
• Repairing damaged parts of trees
• Winter hardiness

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Rootstocks

• Two groups of rootstocks
• Seedling
• Quick and easy inexpensive
• Increased genetic variation (disadvantage)
• Clonal
• Used more in Europe
• Propagated by cuttings, layering, etc.
• Keeps original characteristics

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Graft Union Formation

• Cambial tissues in secure, intimate contact
• Callus tissue formation at edges of cambial
  tissue
• Callus tissue differentiates into cambium (those
  cells in line with cambium)
• Xylem phloem produced

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Callus Tissue

• Thin walled parenchyma
• Lose water rapidly
• Susceptible to insect and disease attack
• Formation
• Most from stock tissue
• Arises from phloem parenchyma immature xylem
  cells
• Torn, dead cells are reabsorbed

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Callus Union
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Graft Unions
Graft Union
Sucker growth from rootstock
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Factors influencing healing

• Graft must be clean from disease virus
• Equipment - may dip in fungicide
• Moisture Temperature
• Temperature Humidity proper for cell growth but
  not to warm (65º-75º F)
• High temperatures - scion buds can break
• Moist peat moss can help or wrapping

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Timing

• Budding
• Best just before bud break
• Important to be able to separate the bark
• Grafting
• Wont heal if root pressure evident (sap flowing)
• Potted plant can be watered less put in cool
  area

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Incompatibility

• May first form a union, then fail
• Two classes
• Translocated incompatibility
• Localized incompatibility
• Interstock insertion can overcome

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Polarity

• Normally distal end of stock to proximal end of
  scion
• Some root grafting, done the opposite
• Water minerals transported, but not organic
  compounds
• Graft union placed below ground so scion forms
  own roots

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Semi-dwarf fruit trees
Honey Crisp Apples
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Topworking orchards
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Topworking

• Simarouba in India (seeds used for oil)

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• Tree roses weeping cherry