Wednesday 18 September 2019

Diarmuid Gavin: Maple magic

Acer is the ace up many a gardener's sleeve - these russet charmers give the finest autumn foliage

Bright red japanese red Ader Palmatum
Bright red japanese red Ader Palmatum

When it comes to arresting autumnal foliage, no tree does it better than the maple (Acer). And while the most common maple - the sycamore - is very big, there's a great selection suitable for average-sized gardens and containers. They make attractive focal points and have year-round appeal, with dramatic changes of foliage colour and beautiful rounded habits, as well as interesting bark in many varieties. Wonderful for creating Oriental gardens, maples look superb beside a pond or in a grouping of trees.

My very favourite is a magnificent specimen which is perched proudly on top of the rockery in Dublin's Botanic Gardens. Maybe I associate it with wonderful memories of being a student in that institution ... or it might just be that the twisted stem and the carefully layered canopy of leaves sum up the often exotic and mysterious nature of many of the plants that have arrived on these islands from far-flung places.

Beautiful as they are, they can also be a source of disappointment when they fail - leaves withering and stem die-back are the most frequent complaints. I think the key to healthy acers is shelter: shelter from wind, frost, drought and blazing sunshine. Imagine them in their natural environment - growing as under-storey plants in a woodland setting - and try to re-create this as much as possible. Ideally they will be in a neutral-to-acidic soil that doesn't dry out, as acers are very shallow-rooting. A thick mulch will help conserve moisture throughout the year. They're fine in containers so long as you water and feed regularly, and use an ericaceous compost.

Protect acers from prevailing winds (which will whip off their leaves in a matter of weeks) by positioning them in a sheltered area. Partial shade is ideal: they can bake on a concrete patio in summer.

Another problem can be scale insect - a brown insect that covers itself in white fluff along the stems; these suck sap, won't kill the tree, but need to be removed by hand. Stems that have completely died should be removed - this sometimes can be caused by a fungal disease, in which case you are eventually going to lose the whole plant. Unfortunately, there isn't a prevention or cure for this: acers are just susceptible to this. If it does happen, remove the plant and don't replant another acer here, as the fungus will probably still be in the soil.

There is a huge variety of acers to choose from - know your soil and your site, and select the most suitable for your garden, bearing in mind the eventual size of your tree. Make a note or take photos when out and about or visiting gardens of varieties that appeal to you, so that when you're shopping at nurseries or garden centres, you can be more specific when choosing your own.

The Japanese maples, Acer palmatum, are some of the most decorative types. I'm growing two at home, one planted by the developers of the estate, which is doing great. Another, which I planted, isn't happy. It's problem most likely is that it's on a south-facing terrace in full sun ... the leaves burn a little and so, this winter, before it establishes too much, it needs moving.

My two, like many of the Oriental maples, have very dissected leaves, which give a very fine, delicate effect. Acer palmatum 'Dissectum Garnet' is one such - its leaves are the colour of a garnet gemstone, turning more scarlet in autumn. It will only grow to about two metres in height over 20 years so will make a beautiful specimen tree in a small garden. A. palmatum 'Atropurpureum' has delicate maple-shaped foliage in a deep burgundy colour. It has an elegant shape and is extremely slow-growing so wonderful for most gardens. Its 'moth wing' seeds that hang on the tree ripen in summer to a gorgeous pink and then a deep red at the end of summer. The leaves always seem to fall simultaneously so that the tree's skeleton is surrounded by a fantastic carpet of luminous red leaves, making a striking picture.

A. palmatum 'Sango-kaku' is the coral- bark maple - like a pop diva, it does several outfit changes: its leaves start off pinky-yellow in spring, turn to green, and finally to yellow in autumn, and the young shoots have coral-pink stems. Another of my favourites is 'Osakazuki', which has very fresh green foliage in summer, turning a very bright orange in autumn.

For beautiful bark, A. griseum, the paperbark maple, has no equal. As the tree matures, delicious ruffles of chestnut bark peel back to reveal copper, cinnamon and orange colours beneath. In addition, it puts on a good autumn display of red and orange - always a pleasure to find one of these in a garden.

If our maples have any leaves left in the wake of storm Ophelia, catch their autumnal show at any of the great Irish gardens, such as the National Botanic Gardens in Dublin and Kilmacurragh (Co Wicklow), Mount Usher in Co Wicklow, Birr Castle in Co Offaly or Blarney Castle Gardens in Co Cork.

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