When to prune acers and magnolias. The two trees that hate spring.

The thing they share, and the thing they don’t

Acers (Japanese maples) and magnolias get lumped together because both punish a badly-timed cut, and for both the worst time is spring. After that the two part company. An acer wants pruning in early winter. A magnolia wants pruning in midsummer, after it’s flowered. Opposite ends of the year, same warning sticker.

The honest first answer for both is: prune as little as you can. Neither tree needs much, and both look best left to their own shape. When you do have to cut, the timing below is what keeps them well.

Acers: prune in early winter, while fully dormant

A Japanese maple is pruned November to January, when it’s completely dormant and the sap is at its lowest. That’s the only window that works cleanly.

The reason is bleeding. Cut an acer in late winter or spring, when the sap is rising, and the wound weeps sap for weeks. It won’t usually kill an established tree, but it stresses it, weakens it, and invites dieback at the cut. People see the buds breaking in March, think “spring tidy”, and that’s exactly the worst moment. Wait until the leaves have dropped and the tree is asleep.

Keep acer pruning light. Take out anything dead, crossing or damaged, shorten the odd wayward shoot, and stop. They make their own elegant layered shape and a hard prune ruins it for years. If a maple has genuinely outgrown its spot, that’s a job for a proper reduction in the dormant window, not a hack in spring.

Magnolias: prune in midsummer, straight after flowering

A magnolia is the opposite. Prune it in July or August, soon after the flowers have finished. Never in winter.

Magnolias heal slowly and resent pruning at the best of times, so you want them cutting at the point in the year when they seal a wound fastest, which is high summer. A winter cut on a magnolia is slow to close and prone to dieback. There’s also no sense pruning before it flowers, since the buds for next spring’s display form on the wood through summer. Cut after flowering and you tidy the tree without sacrificing next year’s show.

As with the acer, go gently. Remove dead or crossing branches, take back anything that’s overhanging a path or a window, and leave the natural shape alone. Magnolias do not want to be boxed or topped.

When the flowers come

Magnolia blossom is the whole point of the tree, and it comes early: March into April, often on bare branches before the leaves, which is what makes the display so striking. A late frost can brown the open flowers in a single night, which is bad luck rather than anything you can prune your way out of. The key thing for timing is simple: prune after the flowers, not before.

Acers don’t do showy flowers. Their season is the leaf, the spring flush and the autumn colour, neither of which is a reason to reach for the secateurs.

You can see both trees’ full year on the tree and hedge care calendar: pick the plant and the prune, avoid and blossom windows are laid out month by month.

A note on East Sussex gardens

Acers and magnolias are both common in the gardens round here, often as a feature near the house where they get noticed and, too often, tidied at the wrong time. A mild coastal spring around Hastings and Bexhill can push the sap and the magnolia buds a week or two ahead of the inland Weald, so watch your own tree rather than the date. If either has grown into the house, a fence or a neighbour’s boundary, that’s a crown reduction done in the right window, and worth getting right on trees this slow to recover.

The short version, if you’re skim-reading

• Both hate being pruned in spring. That’s the one rule to remember.
• Acer (Japanese maple): early winter, November to January, while fully dormant. Cut it in spring and it bleeds sap badly.
• Magnolia: midsummer, July to August, straight after flowering. Never in winter, it heals too slowly.
• Prune both lightly. Dead, crossing and wayward wood only. Neither wants a hard cut or a boxed shape.
• Magnolia flowers March to April, on bare branches. Prune after the flowers, never before.

If you’ve got an acer or a magnolia that’s outgrown its spot somewhere between Hastings, Battle, Bexhill, Rye and Heathfield, send us a note with a photo and we’ll tell you the right month to take it in hand. For any tree or hedge’s whole year at a glance, use the tree and hedge care calendar.