Why Acers Earn Their Place

Few small trees work as hard as the Japanese maple. From the soft bronze of new spring leaves to the fiery crescendo of October, an acer earns its space many times over. In a UK garden, though, they can be divas. Give them what they want and they will reward you for decades; plant them in the wrong spot and you will watch the leaves crisp and the branches die back before you have had a chance to enjoy them. The good news is that the formula is not complicated. Shelter, moisture, drainage and patience with our weather will get you most of the way there.

Choosing the Right Spot

Japanese maples, Acer palmatum and its many cultivars, evolved in the cool, humid woodlands of Japan and Korea, which tells you almost everything about what they need. Think dappled light rather than blazing sun, and a spot that feels calm rather than exposed.

• Light: Morning sun with afternoon shade is ideal. A position that catches full sun from midday onwards will scorch the thinner-leaved varieties, particularly purple and variegated forms.
• Wind: This is the single biggest killer in UK gardens. Cold east winds in spring will shred new growth, and strong westerlies will tear leaves and dry the soil. A sheltered corner, or a position behind a hedge or fence, will make an enormous difference.
• Frost: Acers leaf early, often in March or early April, which leaves them wide open to late frosts. Low-lying spots where cold air pools, such as the bottom of a slope, are best avoided. A gentle slope or a spot near a wall that releases stored warmth overnight suits them well.
• Soil: Moist but free-draining, and slightly acidic to neutral is best. They hate sitting in waterlogged ground in winter and bone-dry ground in summer equally.

Planting and Soil Preparation

Plant bare-root trees between November and March, and container-grown ones at almost any time of year as long as you keep them watered through the first summer. Dig a hole roughly twice the width of the rootball but no deeper than the tree sat in its pot. If your soil is heavy clay, fork in plenty of well-rotted organic matter and consider planting slightly proud, mounding soil around the base to help drainage. If it is thin and sandy, the same organic matter will help hold moisture through summer.

Set the tree so that the point where the roots meet the trunk sits at or just below soil level. Firm gently, water thoroughly, and mulch with a ring of bark or leafmould, keeping it clear of the trunk. A stake is rarely needed for smaller varieties and can do more harm than good if the tie rubs. Water regularly for the first two growing seasons; after that, the tree should be largely self-sufficient, though it will still appreciate a drink in a dry spell.

Feeding and Watering Through the Year

Acers are not greedy. Overfeeding, especially with nitrogen-heavy feeds, produces soft, sappy growth that is a magnet for aphids and very vulnerable to frost. A light hand is best.

• Spring: A mulch of well-rotted manure or compost in March is usually enough. If growth looks weak, a scattering of a balanced slow-release fertiliser or a handful of blood, fish and bone around the drip line will do the job.
• Summer: Keep the soil consistently moist, especially in the first few years and for any tree in a pot. Water deeply and less often rather than little and often, which encourages shallow roots.
• Pots: Container-grown acers need more attention. Use a soil-based compost mixed with grit for drainage, feed with a liquid feed at half strength every few weeks from April to July, and never let the pot dry out completely. A terracotta or glazed pot will keep roots cooler than thin plastic.
• Late summer: Stop feeding by the end of July so growth hardens off before winter.

Protecting Against Wind and Late Frost

This is where UK gardeners earn their stripes. A late frost in May can strip a young acer of every leaf, and while the tree will usually push out a second flush, it costs energy and sets it back. Watch the forecast and, if frost is due once the leaves are out, drape horticultural fleece over the tree in the evening and remove it mid-morning. A simple cloche of fleece on canes works well for small specimens.

Wind protection matters just as much. If your site is exposed, plant a windbreak of shrubs or a hazel hurdle to the prevailing windward side. For potted acers, move them into a sheltered corner or against a wall for winter. In colder spots, a thick mulch around the base will protect roots from penetrating frost, and wrapping the pot itself in bubble wrap or hessian will stop the rootball freezing solid.

Pruning, Pests and Ongoing Care

Prune sparingly. Japanese maples bleed sap if cut in late winter or spring, so the best windows are midsummer, once growth has settled, or late autumn. Remove dead, crossing or damaged branches and thin congested growth to let light into the centre. Avoid hard pruning; these trees look best with their natural shape left intact.

Aphids and vine weevil are the usual troublemakers. Aphids can be blasted off with a hose or left for the ladybirds, and vine weevil grubs, which attack roots in pots, are best dealt with by using a biological control drench in late summer. Leaf scorch, those brown, crispy edges, is nearly always a sign of dry roots, wind or too much sun rather than disease, so treat the cause rather than the symptom.

Get the site right, keep the roots cool and moist, and shield the tree from the worst of our weather, and your acer will settle in for the long haul. There is little in a British garden to match the moment those leaves turn, and once you have seen it happen in your own borders, you will want another one.