Introduction
The purpose of grafting is to combine one plant's qualities of flowering or fruiting (scion plant) with another plant, which has qualities of vigour and resistance (the rootstock). The act of grafting exposes the cambial layer (a thin regenerative layer just below the bark) of each plant and then firmly binds them together. The wound forms a callus, and the scion and rootstock bond to form the new plant. In most cases the plants must be closely related to do this successfully, usually of the same genus e.g. Prunus to a Prunus or Malus to a Malus.
High value ornamental trees such as Magnolia , Acer and conifers are generally container grown. Because they are grafted under cover this is known as bench grafting. Whereas fruit trees and roses are grafted onto rootstock that are growing outdoors in the ground; this is known as field grafting.
Grafting is expensive but most fruit trees are propagated this way because:
- grown on their own root systems many would be excessively vigorous.
- cultivars will not usually breed true from seed.
- a fruiting plant can be produced in a shorter period of time.
- some weak-growing cultivars can be invigorated.
Timing
Different types of grafting are used at different times of year. Chip budding and T budding are undertaken from mid-summer into early autumn, while whip and tongue grafting takes place in late winter or early spring. The latter technique is often used to give a second chance to individual trees, where budding the previous autumn has failed.
The most important things to remember when attempting to graft a plant is to use healthy material, have a very sharp knife that is regularly sterilised and cut straight so surfaces meet flush.
Types of fruit rootstock
The most popular rootstocks today tend to be those with dwarfing characteristics suited to smaller gardens. Fruit trees grown on their own roots or on rootstocks such as Brompton, Malling F12/1, Myrobalan B and MM111 and M2 are vigorous, producing large trees on fertile soils.
Rootstock
Habit
Scion
Soil and training preference
Note
St Julien A
Semi-vigorous
Peaches, nectarines, plums, damson,
apricot
Fan trees for nectarines and peaches. For plums a bush or half standard.
Brompton
Vigorous
Peaches, nectarines, plums, damson
Fan trees for nectarines and peaches
Compatible with all plum cultivars
Colt
Semi-vigorous
Cherry
Fan trained or large tree
Root pruning maybe necessary if tree over vigorous and not fruiting
Gisela 5
Semi-dwarfing
Cherry
Bush, pyramid or fan
Tabel (Edabritz)
Semi-dwarfing
Cherry
Bush, pyramid or fan
Malling F12/1
Very vigorous
Sweet cherry
Fan trained or large tree
Pixy
Semi-dwarfing
Plums, damson
Good as small pyramid or medium tree
Requires generous feeding
Ferlenain
Semi-dwarfing
Plums
Good as small pyramid or medium tree
Similar vigour to Pixy. Prone to suckering.
Mussel
Semi-dwarfing
Plums, damson
Medium tree
Inclined to sucker badly
Myrobalan B
vigorous
Damson, plum
Not compatible with all cultivars
Some resistance to silverleaf
Quince A
Semi-vigorous
Pear
Ideal for most forms
Can tolerate poorer soil than Quince C
Quince C
Semi-dwarfing
Pear
Suitable for fertile soils and vigorous cultivars
Fruits earlier than Quince A
BA29
Semi-vigorous
Pear
Recommended for dry soils
A little more vigorous than Quince A
M27
Very dwarfing
Apple
Fertile soil.
Good for cordons
Always require support.
M9
dwarfing
Apple
Good soils.
Suits dwarf bush, spindlebushes, pyramids and dwarf pyramid trees
Always require support.
M26
Semi-dwarfing
Apple
Most soils. Recommended for containers. Suits bush trees, cordons and dwarf pyramid trees
Support free standing trees for one or two years.
MM106
Semi-vigorous
Apple
Poor soils.
Bush trees, spindebushes, cordons, espaliers and fans
Support for first year or two
MM111
Semi-vigorous
Apple
Medium trees on poor soils
Recommended for poor soils
M25
Vigorous
Apple
Larger trees
Whip and tongue grafting
Whip and tongue grafting is used for the production of fruit stock and some ornamentals. It is normally undertaken in March or early April on rootstocks planted 12 months previously. This technique uses two cuts on both the scion and the rootstock, which enables the two parts to be 'locked' together. This gives a structurally strong graft suitable for field conditions.
In December/January select healthy and vigorous shoots from the scion tree. Note that both rootstock and scion material need to be about the same diameter - preferably 2.5cm (1in). Remove a 23cm (9in) length by cutting just above a bud on the tree. Bundle five or six scions together and heel them into a well-drained, sheltered site leaving 5-7.5cm (2-3in) showing above the soil. This will keep them moist but dormant. Alternatively, wrap them up in a dry plastic bag and keep them in the fridge until spring.
In February, before bud break, cut the top off the rootstock at about 15-30cm (6-12in) above ground level. Trim off the sideshoots. Make a 3.5cm (1.5in) upward-sloping cut on one side that exits half way through the stem. Follow this with a downward cut one-third of the way down the exposed face of the first cut. Make this 5mm (0.25in) deep to form the 'tongue' into which you will insert the 'tongue' of the scion.
The scion (three to four buds long) is prepared by making a flat sloping cut 5cm( 2in) long, just behind a bud. Follow this with an upward cut 5mm (0.25in) deep to form the corresponding 'tongue'. Both are brought together with the tongues interlocking. Match the two cambiums together as well as possible and bind firmly with grafting tape or raffia. Remove this when a callus is clearly visible (about eight weeks).
