The attractive delicate foliage of Japanese maples (Acer palmatum) is prone to leaf scorch. Cultivars with heavily dissected foliage are particularly prone. Scorch occurs following environmental stresses, such as drying winds, and leads to the foliage turning brown.

Plants affected Japanese maple are mostly affected and some other maples through frost, drought, drying winds and hot sun, mostly during spring to autumn.

Leaf scorch rarely causes long-term damage, but it can leave an affected tree unsightly for the remainder of the growing season. Scorch happens whenever water is lost from the leaves more quickly than the roots can take it up. A wide range of environmental factors can cause this such as frost, drought including under-watering, waterlogging, drying winds, hot sun and even salt-laden winds in coastal areas.

Symptoms:
The foliage on affected trees turns brown, particularly around the tips and margins. It is often followed by the leaves curling and shrivelling. In some cases whole leaves can become entirely crispy and there may be some minor die-back of branches. While Japanese maples are most commonly affected, other maples such as Acer pseudoplatanus ‘Brilliantissimum’ and Acer platanoides 'Drummondii' may also suffer from leaf scorch.

Avoiding Leaf Scorch:

• Choose a sheltered spot protected from strong, midday sunshine
• Plant in moisture-retentive but well-drained soil
• Avoid planting in wet soils or on sites that are prone to drying out
• Use a soil-based compost such as John Innes No 2 if planting in containers
• Don’t feed too early or too late in the season (don’t feed between November and March)
• Avoid over application of high nitrogen fertilisers
• Keep newly potted plants well-watered
• Mulch around the base of trees with organic matter, such as garden compost, to help retain moisture for the early part of the growing season until new leaves have hardened. Make sure the mulch is kept away from the trunk
• If frost is forecast when the leaves are newly emerged, move container plants to a sheltered spot or frost-free area and cover plants in the ground with a double layer of fleece
• In very windy weather, a temporary windbreak is a worthwhile

Dealing with Acer Leaf Scorch:

• If leaves become scorched, move the pot to a more sheltered position
• Remove affected leaves gently leaving petiole in place. Badly affected foliage may drop of its own accord and remember that all the leaves will be shed in the autumn regardless
• Prune out dead shoots between late summer and mid-winter. Pruning at other times may lead to bleeding