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What is grafting

00:00 Tue 19th Feb 2002 | Home & Garden

A.� Grafting is a method of plant propagation where simpler methods like taking cuttings or growing from seed are either unsuccessful or too time-consuming.

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It is commonly used for growing and developing new roses and is particularly useful in preserving rare or special plants or controlling a plant's growing habits, especially those of fruit trees. People quite often use grafting as a means of propagating a new specimen of a favourite tree when they are moving house.

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Q.� How does it work

A.� Grafting has memorably been described as the horticultural equivalent of a piggyback. The graft (known as the scion) borrows the stronger legs of the stock or rootstock, the plant that is providing the root system.

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Basically what happens is that the stock, the roots, collect the raw materials, water, nutrients etc and pass them up to the scion which uses them in exactly the same way as it would if it was growing on its own roots. So it is that the plant that grows above the graft retains all the original characteristics of its parent plant.

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It works in reverse too with the rootstock receiving and the food from the grafted parts leaves and in the same way as it would had they come from its own leaves.

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Q.� Could you graft anything on to anything

A. No. Think of grafts as a form of transplant; the two parts have to have some sort of compatibility for the operation to work. The closer the two are the more likely the graft is to work. For instance, you couldn't cross and oak tree with a pear tree but you can cross a pear tree with a quince tree, as they are closely related.

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Q.� But you can grow fruit trees from seed and roses from cuttings, so why graft

A.� With fruit trees the point is to control their height and vigour. Grown from seed or cuttings your average apple tree will vary in size and characteristics. Graft them onto specific rootstock and you can dictate whether they are dwarf, medium or tall.

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The rootstock can also dictate how quickly they bear fruit. For instance, a naturally vigorous variety will take years to produce fruit, but put on a dwarf rootstock and they will be producing within a few years.

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For instance, in apples the most common is known as MM106 (the letters refer to rootstock that has been developed to be virus resistant), which is semi-dwarfing, usually producing trees to about 15ft. M25 is dwarfing, up to about 10ft, while M26, M27 and M9 are smaller, often used to produce cultivars for container growing, and will need supporting. M111 is the most vigorous and is often used for poor soils where it can still produce trees to about 13ft.

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Cherries have Colt (tall) and the self-explanatory Pixie, Pears Quince A (tall) and Quince C (slightly smaller) and so on.

Q.� So how do you do it

A.� In December, choose pencil thick shoots that have grown the previous year and cut them into pencil sized lengths. Wrap them in a piece of damp sacking and store in a cool dark place or bury them wetted peat until March.

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This is the time to start grafting, when the rootstock is active but the scion dormant. Grafting rootstock for roses and fruit trees can be bought from specialists. You can either look through your local gardening press, ask at the local garden centre or trawl the net.

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When it comes to the time to graft cut the rootstock diagonally to expose a fat surface about one or two inches long with a sharp knife using one, clean upstroke. About one-third of the way in from the heel, the upper most part of the surface, make a slit or cleft running towards the middle. This is the tongue.

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Repeat the same process with the scion and join them together by slotting the tongue of the scion inside the tongue of the rootstock.

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Secure the join with raffia or waxed yarn or tape and then use wax or a tree wound compound to seal the whole thing like a plaster.

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If you've got a question about your home or garden, click here.

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�By Tom Gard

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