Choosing Apple Rootstocks

When you buy an apple tree in the UK, you're really buying two plants joined together: a named variety on top, and a rootstock underneath. The variety decides which apples you get — Cox, Discovery, Bramley and so on — but the rootstock quietly decides how big the tree grows, how soon it fruits, and whether it'll cope in a pot. Get it right and your tree fits the space; get it wrong and you've a 4m tree wedged into a small garden.

This is the one number to check on the label before you buy. Here's what each rootstock means in plain terms.

What a rootstock is

A rootstock is the root system your apple variety is grafted onto. Nurseries do this because most apple varieties grown on their own roots make large, slow-to-fruit trees. By grafting the variety onto a chosen rootstock, the grower controls the tree's final size — this is called the rootstock's vigour.

Apple rootstocks have standard codes (M and MM numbers) developed at East Malling in Kent, so the same code means the same thing whichever UK nursery you buy from. The variety still gives you the apples and decides flavour, picking time and disease resistance — see the main guide to growing apples for choosing those. The rootstock just sets the scale.

The main apple rootstocks and the tree size each gives

These four cover almost everything a UK beginner needs. Sizes are rough heights for a free-standing tree after several years; pruning and soil change things a little.

M27 — very dwarf (pot tree). The smallest in common use, reaching around 1.5–2m. It needs good soil, regular watering and permanent staking, because the roots are too weak to anchor or feed a big tree alone. Perfect for a large pot or a tiny bed. Crops young, often in the second or third year.

M9 — dwarf. A true dwarf at roughly 2–2.5m, and the classic choice for a small, easily netted and picked tree. Like M27 it has brittle roots and needs a permanent stake for life. Excellent, early, regular crops on decent soil.

M26 — small. A touch more robust, making a small tree of about 2.5–3m. It tolerates slightly poorer ground than M9 and still fruits young. Needs staking for the first five years or so, and often longer on exposed sites. A forgiving all-rounder for a small garden.

MM106 — medium / semi-dwarf (standard). The most widely sold rootstock, giving a sturdy 3–4m tree. It's vigorous enough to look after itself once established, copes with average soil and grows away strongly. The trade-off is a longer wait for full cropping and a tree that's too big for most pots.

A quick chooser by space

Work backwards from your space, not the variety:

• A pot or balcony → M27 (or M9 in a really big container). Both stay small enough to manage, but expect to water daily in summer, feed regularly and keep them firmly staked. Our guide to growing fruit trees in pots covers compost, pot size and feeding.
• A small garden border → M9 or M26. You get an easy-to-reach tree you can net against birds, pick standing on the ground and prune without a ladder. M26 is the safer bet on heavier or poorer soil.
• A bigger garden, room to spread → MM106. A proper free-standing tree that needs little fussing once settled, with heavier crops in time.

Why it matters for staking and cropping age

Two practical things follow directly from the rootstock you pick.

Staking. The dwarfing rootstocks — M27 and M9 — make small trees, but their roots are weak and can't hold the tree up in wind. They need a stake for the whole of their life, not just the first year. M26 needs firm support for around five years; MM106 usually only needs a stake while it establishes. Skip the stake on an M9 and a gust can rock or topple a fruiting tree.

Cropping age. The smaller the rootstock, the sooner you pick. M27 and M9 often give their first apples in the second or third year; M26 follows soon after; MM106 takes a little longer to settle before it crops heavily. If you want apples quickly in a small space, a dwarf rootstock earns its keep — just give it the water, feeding and support it depends on.

A quick word on company: most apples need a pollination partner nearby to set a good crop, so a lone tree of either rootstock may crop poorly without a compatible variety flowering at the same time. That's a variety question, not a rootstock one — and it's covered in full in the apple guide, along with planting, feeding and the first few years of pruning.