Quick facts
Every season we are asked to look at a tree that has been going backwards: short growth, small pale leaves, a little dieback, no fault you can name. Scrape the soil from the base and the trunk goes into the ground like a telegraph pole — no widening, bark dark and soft where it has sat wet. That tree was planted eighty millimetres too deep five years ago and has been suffocating in slow motion ever since.
Planting mistakes rarely kill quickly. A hole that holds water, a rootball that never met the soil around it, a buried stem — none produces a corpse in the first summer.
Bad planting does not kill a tree. It just stops it ever getting started.
Dig a square hole, not a round one. On heavy clay a spade polishes a curved wall to a glaze, and roots run round that glaze exactly as they would inside a pot. The corners of a square hole give them a way out.
Make it two to three times as wide as the rootball, and no deeper than the rootball itself. Almost all the roots a tree will ever use sit in the top 300mm of soil and travel sideways, often well beyond the branches. Width is what you buy with your effort; depth is not.
Never dig a sump. Going deeper and filling the bottom with gravel feels like drainage, but in clay it makes a bucket: water runs in, has nowhere to go, and stands round the roots all winter. Plant higher, not deeper.
The root flare is where the trunk stops being a cylinder and widens into the first main roots. It should finish at, or slightly above, the soil surface. This detail matters more than anything else on this page.
Do not trust the compost surface on container stock: plants are potted on repeatedly, and the flare is often 30 to 50mm down. Scrape it back until you feel the roots flaring from the stem. Lay a cane across the hole to check before you commit, and on heavy or wet ground plant proud by 25 to 50mm, blending the soil up to meet the ball.
Roots spiralling round a pot-grown ball carry on spiralling once planted, and can eventually strangle the stem. Tease them free with your fingers; if the ball is hard and matted, make three or four shallow knife cuts down the sides. It looks brutal, but new roots break outwards from the cuts. Bare-root plants want the opposite — spread them over a low mound of soil and trim torn ends to clean tissue.
Backfill with the soil that came out. A rich pocket of bought compost in poor ground recreates the flowerpot effect: roots circle contentedly in the good stuff and never venture beyond it. If you want to improve the ground, improve a wide area, or mulch on top and let the worms take it down.
Firm in layers with the ball of your foot, not your full weight — you are chasing out air pockets, not compacting soil. Then water in properly, 20 to 30 litres for a tree and 10 for a shrub, even if it is raining and even in November. That soak is not about moisture but about washing fine soil into contact with every root.
Mulch a circle at least a metre across, 75 to 100mm deep, with bark or composted woodchip, kept a hand's width clear of the stem; mulch against bark keeps it wet and invites rot. Keep grass out of that circle for three years, because turf competes for water harder than gardeners believe. Stake low and briefly. One stake driven at an angle from the prevailing south-westerly, fixed no higher than a third of the stem, is all that is wanted: the top needs to move, and that movement thickens the trunk and triggers anchoring roots. Take the whole arrangement off after two growing seasons. Fit a spiral guard against rabbits and hares, and against strimmers too — strimmer damage at the base is among the commonest losses we see, and it is silent until the tree fails.
Where drainage is doubtful, choose stock that forgives you. Alnus glutinosa (alder) and Betula pubescens (downy birch) grow in soil that kills most trees, and Amelanchier lamarckii, Viburnum opulus and Cornus alba take seasonal wet in good grace. Cistus, Lavandula and most magnolias want drained feet, and rot in a cold wet hole.
Common mistakes
Ask our team to show you the root flare on a real plant; it is far easier shown than described.
First and foremost, you will need to consider the quantity of plants required to achieve a full looking hedge. We usually recommend 2.5 plants per linear metre for a fully mature hedge. For a semi mature hedge, you can plant 2 plants per metre.
However, different types of hedging plants have different growth habits, so the quantities of plants you may need could vary. it is always best to check with your local nursery.
