Which rootstock should my fruit tree be on?

Every fruit tree you buy is two plants joined together: a variety grafted onto a root system grown from something else. The variety carries the fruit; the rootstock controls vigour, and therefore final height, spread, how many years until the first crop, and how much of your life you will spend on a ladder. It is the single most consequential thing on the label and the one people skip.

What you'll need

• The nursery label or catalogue entry
• A tape measure and an honest look at the space

Step by step

1. Measure the space you actually have, in metres.Not the space you would like. Measure to the boundary, to the house, to the neighbouring canopy, and look up for cables. A tree spreads roughly as wide as it is tall.
2. Pick the rootstock from that number, before you pick the variety.For apples: M27 gives 1.5–2m and must be staked for life; M9 gives 2.5–3m, staked for life; M26 gives 3–3.5m, staked five years; MM106 gives 4–5m and is the standard garden tree; M25 gives 6m and more and is an orchard tree.
3. Translate to the other fruits.Pears: Quince C for a small tree, Quince A for a normal garden tree. Plums, gages and damsons: Pixy for small, St Julien A for normal. Sweet and acid cherries: Gisela 5 for a small tree that can be netted, Colt for a normal garden tree. Old cherry rootstocks such as Malling F12/1 make enormous trees and are not garden material.
4. Check how soon it will crop.Dwarfing rootstocks crop early because they are less vigorous: M27 and M9 in two to three years, M26 in three to four, MM106 in four to five, M25 in six to eight. If you want fruit soon, that argues for the smaller rootstock, not the bigger one.
5. Accept the trade-off that comes with a dwarfing rootstock.A dwarf tree has a small, shallow, weak root system. It needs a permanent stake, it cannot compete with grass, and it will suffer in a drought unless watered. It is not a low-maintenance option — it is a small option.
6. Set the planting distance from the rootstock, not from the pot.As a working guide: M27 about 1.5m apart, M9 about 2.5m, M26 about 3.5m, MM106 about 4.5m, M25 6m or more. Cordons are the exception and go 75cm apart because they are pruned to stay narrow.
7. Read the label properly at the nursery.It should give the variety, the rootstock and the pollination group. If a garden centre cannot tell you the rootstock, you are buying an unknown tree — a specialist fruit nursery always states it, and often ships bare-root at a fraction of the price.
8. Do not plan to control size by pruning.Pruning a vigorous tree hard makes it grow harder. You get vertical water shoots, no fruit, and the same job again next year. Size is bought, not pruned.

Tips

• MM106 is the right answer for most UK gardens: a tree you can pick most of from the ground, tolerant of a range of soils, cropping from year four or five.
• On thin chalk, poor sand or a windy exposed site, go one step more vigorous than the space suggests — the site will hold it back anyway.
• Some nurseries sell the same variety on three rootstocks at the same price. Choosing well costs nothing at the point of sale and everything afterwards.
• A tree already growing in the garden with no label can often be sized by looking at it: if it is over 5m and was planted in the last twenty years, it is on a vigorous rootstock and will not be made small.

Common mistakes

• Choosing the variety first and taking whatever rootstock the tree happens to be on — The same apple is available on several rootstocks. Getting the variety you wanted on a tree twice the size you have room for is the commonest fruit-buying mistake there is.
• Buying a dwarf tree and not staking it permanently — M27 and M9 have brittle, shallow roots and blow over carrying a crop. The stake is part of the tree for its whole life, not a temporary aid.
• Planting a dwarf tree into mown grass — Grass takes the water and nutrients from exactly the shallow zone a dwarfing rootstock roots in. Keep a metre of clear mulched soil around it or it will barely grow.

Questions people ask