When buying an apple tree, don’t just look at which variety will suit you best. It’s also important to be selective about the type of rootstock the variety is grafted on, as this will affect the size and vigour of the tree. These are the most common options:
M27 Very dwarfing Ideal for step-overs, but it needs a rich soil and lots of support. The tree must be staked throughout its life. M9 Dwarfing This makes a small tree, about 2.5m tall, that crops from the second or third year. It’s great for cordons and pyramids in small gardens. Fruits tend to be large and ripen earlier than those of the same variety on a more vigorous rootstock. It needs rich soil and a permanent stake. M26 Semi-dwarfing Used a lot in commercial orchards, as it keeps trees small but with early, large fruits. It can tolerate poorer soil than M9, but is a slow starter and needs staking. Recommended for trees planted in containers. MM106 Semi-vigorous This gives a medium-sized tree, 3-4m tall, that grows well on most soils. Suitable for a semi-standard (with a clear trunk of 1m) or large bush-shaped tree, or espaliers or cordon trees in poorish soil. MM111 Vigorous Ideal for standard or semi-standard trees, up to 4.5m ( smaller on light soils). It can also resist potash deficiency in the soil and is notably resistant to drought. M25 Very vigorous The best choice for a large standard tree, approximately 4-5m tall, which can produce up to 180kg of fruit.