Growing Japanese acers for exceptional autumn colour
Get the expert’s tips on growing these much sought-after trees for ace autumn colour
Here we simplify the mysteries of growing maples and explode the myths that surround them, and provide you with all you need to successfully grow Japanese maples (acers) .
We hope you’ll explore the beauty of these graceful trees, with their stunning colours and majestic forms, by planting one or maybe two!
Are they hardy?
apanese maples are misunderstood. People believe 'they don’t like the wind’ or ‘they don’t like the sun’, yet maples have lived with wind and sun for thousands of years, and if they weren’t compatible with these elements they wouldn’t survive to be the beautiful trees they are today.
In the winter of 2010/2011, the UK experienced temperatures of -20C (-4F), and Japanese maples were one plant that came back fighting. Any that didn’t survive had other underlying problems.
However, when maples break leaf in spring they can be susceptible to air frosts in late April and May. These can burn the leaves, showing a bleach-splattered effect. This won’t kill the plant, but if an air frost is forecast and your maple’s in a pot, move it temporarily to the greenhouse.
Growing Japanese maples in a pot
It’s important to remember not to choose too large a pot or container. Don’t use terracotta pots, as too much moisture is lost through the wall of the pot and the tree will dehydrate, causing brown leaf tips and edges. Always use glazed stone/ceramic or plastic with good drainage holes. ● If you’re potting on from a one litre pot, only move up to a maximum of a 2-litre pot, which will be sufficient for one season’s growth. Then from a two litre to three litre, and three litre to five litre – and from then on move onto a container that's just big enough to get the flat of your hand down between the rootball and the side of the new pot. ● Repot in spring just as the leaves are about to break, or in August when top growth is starting to slow down. Potting on can be carried out midseason, but may cause browning of the leaves as the roots adapt themselves to the environment of the new compost. Don’t repot Japanese maples in autumn when the leaves have dropped as they’ll make very little root, and the existing roots could become damaged and rot away. ● If you’re using a tall planter, don’t fill the whole depth of the pot with compost as this will cause the rootball to rot over time. The bottom threequarters of the planter should be filled with coarse stone or bricks for stability and only the top quarter should be filled with well-drained, multi-purpose compost. ● In pots they need feeding through their growing season. Between May and July we use Miracle Gro liquid feed once a month. From August until the end of September use tomato feed, which will harden off soft growth ready for winter.
The biggest threat to potted maples is being left out in winter and being allowed to get waterlogged; this in turn rots the fine root system, which enables them to grow successfully in containers in the first place.
To avoid this happening, as soon as your maple has dropped its leaves in autumn, the tree and container should be moved to a position sheltered from rain. This must still be outdoors with free air movement all around. Don’t wrap up your maple as this will cause bacteria to form. Remove any dishes that the pot’s standing in, to avoid collecting water. Pots should be raised off the ground to stop water being drawn up into the pot. Don’t water your maple again until the buds begin to break in the spring, and only very sparingly to start, increasing as the leaves unfold and the weather improves. Protect from late frosts.
Maples don't need large pots – they can be planted in shallow containers – but avoid terraco a as these lose moisture
Japanese maples won't put down deep roots in the garden and stay compact, too
When po ing acers into tall pots, fill three quarters with drainage material and the rest with multi-purpose compost