Grafting and budding methods
How grafts unite, choosing rootstocks and scions, the main grafting and budding methods with crops, compatibility, aftercare, and a nursery success sum.
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Almost every apple, mango, orange, avocado, rubber and rose plant sold by a nursery is two plants joined into one: a rootstock below, chosen for its roots, and a scion above, the variety that bears the fruit or flowers. Grafting joins a shoot piece to the rootstock; budding joins a single bud. Together they allow growers to propagate varieties true to type, bring trees into bearing early, and combine the best roots with the best fruit.
Grafting and budding methods are among the most practical and most examined topics in horticulture.
Why graft?
- Propagate clones of varieties that do not come true from seed or root poorly from cuttings.
- Use rootstocks for tree size control (dwarfing apple rootstocks such as M.9), resistance to soil pests and diseases (phylloxera-resistant grape rootstocks, Phytophthora-tolerant citrus and avocado rootstocks), and tolerance of salinity, drought, waterlogging or calcareous soils.
- Hasten bearing, since the scion comes from mature wood.
- Top-work old or unproductive trees to a new variety.
- Repair damaged trees (bridge and inarch grafts).
- Grafted vegetables: tomatoes, eggplants, cucumbers and watermelons grafted onto vigorous, disease-resistant rootstocks are widely grown in East Asia, Europe and greenhouses elsewhere, mainly against soil-borne diseases.
How a graft unites
- The cut surfaces are placed so that the cambium, the thin layer of dividing cells between bark and wood, of scion and rootstock touch.
- Both partners produce callus cells that interlock and fill the gap.
- New cambium forms across the callus, joining the cambium of the two partners.
- The new cambium produces xylem and phloem that connect the two vascular systems.
The essentials of success are therefore: compatible partners, cambial contact, close, firm tying, protection from drying (wax, tape or plastic), the right physiological stage (active growth for budding; often dormant scions on actively growing rootstocks for grafting), and correct polarity (scion the right way up).
Grafting methods
| Method | Description | Typical uses |
|---|---|---|
| Whip-and-tongue | matching sloping cuts with interlocking tongues on stems of similar diameter | apple, pear on young rootstocks; bench grafting |
| Cleft | scion with a wedge-shaped base inserted in a split in a thicker rootstock | top-working trees; mango, cashew |
| Softwood or wedge | cleft grafting with young, green shoots | mango, sapota, cashew nurseries; grafted vegetables |
| Veneer (side) | scion set into a shallow cut on the side of the rootstock | mango, conifers, ornamentals |
| Bark | scion slipped under the bark of a thick stock when the bark lifts | top-working large limbs |
| Approach (inarching) | two rooted plants joined while both still on their own roots, then the scion is cut free | difficult species; traditionally mango; repairing trees |
| Bridge | scions span a girdled section of trunk | rescuing trunks damaged by rodents or machinery |
| Tube or splice | stems joined end to end with a clip or tube | grafted vegetable seedlings |
| Epicotyl or stone | grafting onto the very young shoot of a germinating seed | mango, cashew, walnut |
Budding methods
Budding uses one bud with a small shield of bark, which makes efficient use of scion wood:
- T-budding (shield budding): a T-shaped cut in the rootstock bark, which must lift easily ("slip"), receives a shield bud. Used for citrus, rose, apple, peach and many stone fruits.
- Patch budding: a rectangular patch of bark with a bud replaces an identical patch on the rootstock. Used for thick-barked species such as rubber, mango, ber and pecan.
- Chip budding: a chip of bark and wood with a bud fits a matching notch. Works even when bark does not slip; widely used for apple and pear in European nurseries.
- Ring and flute budding: variations for thick-barked trees.
After the bud unites, the rootstock is cut back above it (heading back) to force the bud to grow.
Compatibility
Grafts usually succeed only between closely related plants: within a species, often within a genus, and occasionally within a family (quince as a dwarfing rootstock for some pears). Incompatibility shows as poor union, yellowing, overgrowth at the union, early decline or the scion snapping off at the union, sometimes years after grafting. Some incompatibilities are caused by viruses that the rootstock tolerates but the scion does not, such as citrus tristeza virus on sour orange rootstock, which killed millions of citrus trees in South America and elsewhere.
Rootstock–scion interaction
The rootstock affects the scion's vigour, size, precocity, yield, fruit size and quality, nutrient uptake and stress tolerance. Dwarfing apple rootstocks from the East Malling and Merton programmes in England, such as M.9 and MM.106, made modern high-density orchards possible. The scion in turn affects root growth by supplying sugars and hormones.
Planning grafted plant production
A nursery must deliver 5,000 grafted mango plants. Softwood grafting succeeds on 75 per cent of rootstocks, and 10 per cent of successful grafts are lost or culled before sale.
- Grafts needed = 5,000 ÷ (0.75 × 0.90) = 5,000 ÷ 0.675 ≈ 7,410 rootstocks to graft.
- If rootstock seeds germinate at 80 per cent and 5 per cent of seedlings are too weak to graft: seeds = 7,410 ÷ (0.80 × 0.95) ≈ 9,750 seeds.
- A skilled grafter making 400 grafts a day needs about 7,410 ÷ 400 ≈ 19 working days.
Improving graft success from 75 to 85 per cent would cut the rootstocks needed to about 6,540, saving nearly 900 seedlings and two days of work.
Aftercare
- Keep grafted plants in shade and high humidity for the first weeks, often under plastic.
- Remove sprouts from the rootstock below the union regularly.
- Loosen or remove ties once united, before they girdle the stem.
- Stake young grafted trees and plant them with the union above soil level, or the scion may root and lose the rootstock's benefits.
Key points
- Grafting joins a scion to a rootstock; budding uses a single bud.
- Union depends on cambial contact, callus formation and new vascular tissue.
- Grafting methods: whip-and-tongue, cleft, softwood/wedge, veneer, bark, approach, bridge, tube, epicotyl.
- Budding methods: T (shield), patch, chip, ring and flute.
- Rootstocks control size, pest and disease resistance and stress tolerance; compatibility requires close relationship.
- Plant with the union above soil and remove rootstock sprouts.
What the exams ask
- School-leaving and entrance papers: definitions of grafting and budding, their advantages, and common methods with examples.
- Degree and research-fellowship entrances: graft union formation, compatibility and incompatibility, rootstock effects, methods for specific crops, and vegetable grafting.
- Professional and nursery examinations: planning grafted plant production, aftercare, and certification of rootstocks and budwood.
Described in general terms: the kind of examination, not a past paper. Laisha never reproduces exam questions.
Questions people ask
When is the best time to bud?
When the rootstock's bark slips easily, during active growth, and when suitable buds are available on the scion variety. Chip budding is more flexible because it does not need slipping bark.
Why are suckers from below the graft a problem?
They come from the rootstock, so they bear rootstock fruit or flowers, and they compete with the scion. Remove them promptly.
Can I graft any fruit onto any tree?
No. Only closely related plants unite well, such as orange on other citrus, or pear on pear or quince. Unrelated combinations fail.
Sources
- Hartmann, H. T., Kester, D. E., Davies, F. T., Geneve, R. L. and Wilson, S. E. Hartmann and Kester's Plant Propagation: Principles and Practices, 9th edition. Pearson, 2018. Chapters 11–13.
- Garner, R. J. The Grafter's Handbook, 6th edition. Chelsea Green, 2013.
- Lee, J.-M. et al. "Current status of vegetable grafting: diffusion, grafting techniques, automation." Scientia Horticulturae 127, 93–105 (2010).
- Webster, A. D. "Rootstock and interstock effects on deciduous fruit tree vigour, precocity, and yield productivity." New Zealand Journal of Crop and Horticultural Science 23, 373–382 (1995).
- Moreno, P. et al. "Citrus tristeza virus: a pathogen that changed the course of the citrus industry." Molecular Plant Pathology 9, 251–268 (2008).
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