St Nicks

Centre for nature and green living

March 2016: Spotlight on…Acers

Sycamore bud burst

Sycamore bud burst

Members of this large and widespread group of trees can be identified by buds and leaves in opposite pairs, and clusters of small flowers opening with or just before leaves which are normally hand-shaped with three, five or seven lobes. The seeds are in winged pairs that often spin as they fall to the ground – popularly called keys , spinning jennies or helicopters. Three species have been identified at St Nicks. Field Maple and Sycamore occur in most of the wooded areas, but the most notable Sycamore is a large, multi-trunked specimen near the Dragon Stones. Field Maple is probably easiest to find along the grass path next to the meadow, where the only known Box Elder also grows.

Sycamore, Acer pseudoplatanus, is a large, broad-crowned tree introduced from central Europe in the 16th century. Younger trees have smooth, light coloured bark that tends to become scaly as the trees age. The buds are green throughout winter, sometimes tinged with pink. The leaves are quite broad with toothed edges and a rather coarse texture. In late summer they often have large black spots caused by the tar spot fungus, which disfigures the tree but doesn’t seem to do it any harm. The green flowers are clustered into quite dense panicles, and the wings of the seeds make something close to a right angle. The seeds have a very high germination rate, making Sycamore a nuisance weed in some locations. If you have a lawn or grass verge with a Sycamore nearby, you’ll notice how in late winter and spring the seed wings start to stand on end as the seed puts out its first root and anchors itself into the ground. The other factor that can make Sycamores unpopular, as anyone who has ever parked under one in summer will know, is that aphids are attracted to their sap, and the resultant “honey dew” drops a sticky layer on to anything underneath. The name “pseudoplatanus” refers to the tree’s superficial similarity to a Plane tree, while the word Sycamore apparently comes from a totally unrelated species of fig thought to have similar leaves.

Field Maple, Acer campestre, is our only native species of Acer. It’s a smaller tree than Sycamore, with smaller, crisper leaves, roughly the same shape but with untoothed edges and a smoother texture. The wings of the seeds are horizontal with upturned ends, and the flowers form smaller, less dense clusters. Like Sycamore, the bark is smooth when young but cracks as it ages, and mature twigs can develop a corky appearance. Unlike other native trees, Field Maple doesn’t seem to have attracted any important folk lore, and has limited herbal properties. Apologies for lack of photos of this tree!

Box Elder, Acer negundo is another non-native species, this time native to North America. It’s less obviously a member of the maple family, with leaves that at first sight look more like elder, with pairs of leaflets.

Box Elder flowers

Box Elder flowers

Its flowers are deep red, in smaller clusters than Sycamore but denser than Field Maple. The seeds, which often hang in clusters after the leaves have fallen, are shaped rather like a wishbone with the ends of the wings turned slightly inwards. It gets its name from the appearance of the leaves and the fact that its wood is similar to boxwood – though in North America it is also called Ash-leaved maple.

Acers in general and Sycamores in particular are often assumed to be of limited ecological value. However, their aphid colonies are a useful food source for birds, hoverflies, lacewings and ladybirds, their flowers provide nectar and pollen for bees, several species of moth feed on the leaves, and small mammals will nibble the fallen seeds. Field Maple and Sycamore will tolerate pollution so are useful trees for urban areas. All three provide valuable timber – Sycamore is said to be particularly good for kitchen equipment. Field Maple has a density suitable for items like harp frames, and according to one source Antonio Stradivari used it for his famous violins. Box Elder features in a range of traditional Native American woodwork.

20 March 2016 | Categories: Spotlight on..., Wildwatch