How to Plant an Apple Tree: Rootstock, Spacing and Graft Union

The rootstock decides the size, not the variety

Every apple tree you buy is two plants joined together: a variety grafted onto a rootstock. The variety gives you the fruit. The rootstock gives you the final height, the age at which the tree starts cropping, how deep it roots, and whether it will stand up on its own. Two trees of the same variety on different rootstocks can finish up eight feet apart in height.

This matters most in a small garden, because a vigorous rootstock cannot be pruned into a dwarf. Trying to keep a large tree small by cutting it back hard produces a thicket of upright water shoots and no fruit. If the label on your tree names a rootstock, write it down now; it tells you your spacing, your staking and your pruning for the next twenty years.

If you have already planted and do not know the rootstock, judge by growth. A tree putting out more than three feet of new extension growth a year on a mature framework is on something vigorous and needs summer pruning and wider spacing than you gave it.

Dwarfing rootstocks have brittle, shallow roots and never become self-supporting. A dwarf tree that has lost its stake will lean further every year and eventually blow over in fruit.

Choosing the spot

Apples want full sun, at least six hours a day and preferably eight. Shade does not stop the tree growing; it stops fruit buds forming and it keeps the leaves wet longer, which is what scab needs. A tree on the shaded side of a building will make wood for years and give you a handful of small, dull-colored apples.

Drainage matters more than soil richness. Apples will not tolerate roots sitting in water, and a hole that still holds water twelve hours after you fill it is telling you to plant on a raised mound instead. Aim for soil that drains freely but holds moisture, with a pH around 6.0 to 6.8.

Avoid frost pockets. Blossom is killed at around 28F (-2C), and cold air runs downhill and pools at the bottom of a slope or behind a solid fence. Planting halfway up a slope, where the cold air keeps moving past, saves crops in a late frost year. Also allow for wind: heavy wind at bloom keeps pollinating insects grounded, and later in the season it strips fruit off the tree.

Planting a bare-root or potted tree

Bare-root trees go in during dormancy, from leaf fall until the buds move in early spring, whenever the ground is neither frozen nor waterlogged. Container-grown trees can go in at any time the ground is workable, but they still establish best planted dormant. Get the roots into the ground the day they arrive; if you cannot, heel them into damp soil rather than leaving them in a bag.

1. Dig wide, not deep Make the hole two to three times the width of the roots but no deeper than the roots are long. A wide, shallow hole with roughened sides is what roots spread into. A deep hole simply lets the tree sink.
2. Do not enrich the hole Backfill with the soil you dug out. Filling the hole with compost or fertilizer makes a pot in the ground that roots circle inside instead of pushing out into the surrounding soil. Save the compost for a surface mulch.
3. Keep the graft union above the soil Find the swollen kink low on the trunk. Set the tree so this sits four to six inches (10-15 cm) clear of the finished soil level. Bury it and the variety roots above the graft, the dwarfing effect is canceled, and you get a full-size tree.
4. Spread the roots and firm in stages Lay the roots out flat rather than curling them round the hole. Add soil in layers, firming each with your heel and shaking the tree gently so soil fills the gaps between roots. Air pockets are what kill bare-root trees.
5. Water in heavily Give at least four gallons (15 L) slowly, even in wet weather. This is not about moisture; it is to settle the soil into contact with every root. Top up any hollow that appears.
6. Mulch, but keep it off the trunk Spread two to three inches (5-8 cm) of compost or bark in a circle three feet (90 cm) across, leaving a clear hand's width of bare soil against the trunk. Mulch piled against bark holds damp and invites canker and voles.

Keep that three-foot circle free of grass for the first four years. Grass competes for water and nitrogen at exactly the depth young apple roots occupy, and it slows establishment more than almost anything else you can do wrong.

Staking and the first two seasons

Drive the stake in before you backfill, on the side the prevailing wind comes from, so you never drive it through the rootball. For a dwarf tree use a tall stake reaching into the head of the tree and leave it permanently. For a semi-dwarf or larger, a short stake reaching about a third of the way up the trunk is right: the top of the tree needs to flex, because flexing is what thickens the trunk.

Tie with a proper adjustable tree tie and a spacer, and loosen it every year. A tie left alone for three seasons will girdle the trunk, and a tree that dies from a forgotten tie dies from the top down while looking healthy at ground level.

In the first summer, water deeply once a week in dry spells rather than lightly every day, giving four to five gallons (15-20 L) each time. Deep, infrequent watering pulls roots downwards. Hold off on nitrogen until the tree has made new growth; feeding a tree that has not yet rooted just burns it.

Plant a partner, or plan for one

Almost no apple sets a decent crop from its own pollen. Unless you already know there is another apple or a crab apple flowering nearby, plant a second tree whose bloom overlaps with the first. A hundred feet (30 m) apart is close enough for bees; across a garden fence counts. This is the single most common reason a healthy, well-pruned apple tree carries no fruit.

If you only have room for one tree, a family tree with two or three varieties grafted on one trunk solves it, as does a container-grown crab apple stood next to the tree while it is in flower.

What to write down at planting

Record the planting date, the rootstock name from the label, the variety, the flowering group, and which way the tree faces relative to the sun and the prevailing wind. In four years, when you are deciding how hard to prune or why one side crops better than the other, none of that is recoverable from looking at the tree.

Add a note of the finished soil level against the trunk and the height of the graft union. If the tree later starts growing more vigorously than the rootstock should allow, the first thing to check is whether it has settled and rooted from above the union.