Why the early years matter so much

A tree is at its most forgiving in its first five years. Cut a young sapling back hard and it shrugs, throwing out new growth from buds you had forgotten were there. Leave the same fault in a thirty-year-old oak and you are looking at a chainsaw, a climbing ticket and a bill that could have been avoided with ten minutes of work and a decent pair of secateurs.

Formative pruning is simply the craft of steering a young tree while the steering is still light. You are not trying to sculpt a topiary shape; you are removing the structural faults that would otherwise become expensive problems. Narrow-angled joints that split in a gale. Two trunks wrestling for the same space. A branch rubbing a neighbour raw. Deal with these in the nursery years and the tree carries a strong, well-spaced framework for the rest of its life.

Choose one leader and be firm about it

Most young trees want to grow into a fork. Two shoots race upwards from near the same point, each convinced it is the trunk. Left alone, this becomes a co-dominant stem, and the union between the two is often weak — a V-shaped joint with bark trapped inside it, which is exactly where rots and splits begin.

So pick your leader. It should be the straightest, sturdiest stem, growing vertically and showing no sign of dieback or damage. Then remove the competition:

• Cut out any rival stem that is nearly as thick as your chosen leader.
• Remove shoots growing from the base of the trunk — they sap vigour and confuse the shape.
• Trim back any side branch that is starting to outgrow the leader, cutting to an outward-facing bud or a weaker side shoot.
• On grafted trees, rub out suckers from below the graft union as soon as you see them.

Where a choice of leaders exists but neither is ideal, pick the better one and shorten the other hard, rather than removing it entirely. It then acts as a temporary sap drawer while the leader thickens.

Deal with crossing, rubbing and damaged wood

Run your hand along the branches and look for wood that is touching. A branch that rubs against another opens the bark every time the wind blows, and that wound is an open door. Remove the weaker, thinner or more awkwardly placed of the pair, taking it back to the trunk or to a strong outward-going side shoot.

The same rule applies to:

• Branches that grow back towards the centre of the tree, crowding the middle.
• Dead, diseased or snapped wood, which should always go first.
• Branches with an awkward upward kink or a history of dieback.
• Lowest limbs you will never want, on a tree destined to be walked beneath. Remove these gradually — no more than two or three a year.

Keep the branches that are well spaced, growing outwards and upwards at a comfortable angle — roughly between four and ten o'clock on a clock face. Those are the ones that will carry the canopy.

Timing, tools and clean cuts

For most deciduous trees, the dormant season from late autumn to late winter is ideal. The tree is not pushing growth, the framework is easy to see without leaves, and wounds begin sealing as the sap rises in spring.

The exception in Britain is anything in the Prunus family — cherry, plum, damson and their ornamental cousins — along with walnut. These are best pruned in late summer, from roughly July into early September, when the risk of silver leaf and bleeding is at its lowest.

Whatever the season, technique matters more than brute force:

• Use sharp bypass secateurs for stems up to finger thickness, loppers for anything larger, and a pruning saw for branches over about five centimetres.
• Cut to the branch collar, the slight swelling where branch meets trunk. Do not leave a stub, and do not cut flush — the collar is the tree's own healing tissue.
• When shortening a leader, cut just above an outward-facing bud, at a slight angle, so the new shoot grows away from the centre.
• Take no more than about a quarter of the canopy in any one year. Slow and steady builds a better tree than a single drastic session.

Building the framework over several years

The first year is mostly about the leader. In the second and third, you start selecting what foresters call the scaffold branches — the permanent limbs that will carry the crown. Aim for a spiral arrangement up the trunk, ideally a good thirty to forty centimetres apart vertically, with no two branches emerging from the same height on the same side.

Temporary branches low down are not wasted growth. They help thicken the trunk and shelter it from sun. Leave them, shorten them a little each year, and remove them only once the tree is established and the trunk can stand on its own.

Aftercare and the discipline to do less

A pruned young tree wants a mulch ring kept clear of grass, a good soak in dry spells, and a stake that is checked and then removed after two or three years — trees left staked too long grow weak at the base. Check ties annually for rubbing.

And resist the urge to fiddle. Once the leader is clear, the crossings are gone and the framework is spaced, put the secateurs down and let the tree get on with it. A little restraint now is what gives you a straight, sturdy, long-lived tree in the decades to come.