A Blaze of Japanese Acers
by Sally Gregson

Of all the trees and shrubs that colour in autumn it’s the Japanese acers that have the most ‘wow’. It only takes a few nights of sub-zero temperatures to shock their leaves into a fiery blaze of glory that lasts until the first high winds knock them down.

In their native Japan, ‘momiji’, the viewing of autumn colour, draws the crowds to the temple gardens just as the cherry blossom does in spring.
Red, orange and yellow acers are planted in velvet, luminous green moss; their impact doubled in the reflections of still, serene water.
It’s a trick that works well in any garden. The divided foliage of Acer palmatum dissectum cultivars have a tendency to cascade down in lacy tiers of foliage that just asks to overhang a pond.
Try planting mounds of A. p. ‘Dissectum Nigrum’ with its deeply-cut maroon leaves, that flash red in autumn, with tall toad lilies (Tricyrtis) behind and a carpet of Cyclamen hederifolium beneath. Or Acer p. dissectum ‘Green Lace’, that fades gold, would contrast richly with sapphire and turquoise gentians in acid soil. And the less divided red leaves of A. p. ‘Atropurpureum’ is another classic combination with Japanese painted ferns such as Athyrium otophorum ‘Okanum’ with red-veined, yellow fronds, and A. nipponicum ‘Pictum’, again with red veins and silvered fronds.

Containers

Over time these essentially dwarf acers develop gnarled, twisted trunks that make them ideal for bonsai or for a large container. In particular the cream-margined leaves of A. p. ‘Higasayama’ turn yellow, orange and red in autumn and would make quite a splash in a shady corner.
Or try putting A. p. ‘Orange Dream’ in a dark green ceramic pot. Its lemon yellow leaves, with orange-red tips, colour well in autumn too.
All Japanese Acers have a dense, fibrous root system that prefers to be tightly contained, so don’t put a small, young acer into a large pot immediately. It’s better to wait until its roots fill the container. This is best done in spring, so the plant has the whole growing season to use up the new space. Once it reaches its final pot-size, it will be perfectly happy to live there as long as it’s fed every spring, and watered regularly.
Acers can be rather unforgiving if they are dried out or put in a windy position. The more delicate the foliage, the more quickly the leaves desiccate and turn brown at the edges.

Pruning

If your acer needs a little pruning and shaping, it’s important to undertake this in the winter. They notoriously bleed sap while they are growing which can cause the stems to die back. Occasionally, if the plant has been put under stress, the rootstock will produce a strong, healthy shoot below the graft union. Cut off the ‘sucker’ flush with the trunk to prevent the more vigorous rootstock taking over.
Variegated acers sometimes throw out an all-green shoot, a ‘reversion’, which will grow more vigorously than the variegated branch. If the green-leaved shoots are not removed they, too, will take over.

Cultivation

Acers are hardy, easy shrubs to grow, provided they are planted in right place:
They are essentially woodland plants that need shade from the midday sun
They should be sheltered from high winds.
They prefer a draining soil that is full of organic matter to retain some moisture without becoming waterlogged.
The pH, that is the acidity/alkalinity of the soil, is not important. A dose of ‘Sequestrene’ should bring any colour back to their cheeks if their leaves become yellowed between the veins.
For pots and containers use a mixture of all-purpose and loam-based compost. And every spring thereafter water with a well-balanced liquid feed.