Grafting Fruit Trees

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).

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