Tree of the Year 2015 - Field Maple (Acer campestre)
This year we celebrate a small and slender tree easily overlooked and often ignored: the field maple (Acer campestre). The trunk is usually too slim to be of use in forestry and the wood too similar to that of Norway or sycamore maple to create an interest. And yet it is time to take a closer look at this species. It is in the city that it shows off its strong suit – and here it will become increasingly important in the future.
It grows slower than many other species, and in comparison to its maple «brothers» it remains small and is characteristically gnarly. 20 metres? Field maple rarely makes it or takes a long time over it (only in forests where it is forced to compete with other trees it can sometimes grow up to 25 m). It also often grows several trunks instead of just one or even takes a shrub-like shape. You will often encounter a small group of field maples – they can of course develop from individual seeds, but often they are in reality part of only one single tree.
Young branches frequently carry suberized ribs which, close to the leaf or bud, all of a sudden narrow down strikingly as if strangulated – an impressive feature. On the trunk, the bark turns scaly, covered in small rectangular patterns. The trunk almost always shows striking bulges and hollows.
Like the Norway and sycamore maple, field maple trees can live up to about 200 years. They achieve 70 cm in diameter but rarely exceed full meter – the biggest I ever came across was 1,15 m (3,60 m in girth), which means the tree would come fifth on the list of champion trees in Germany.
These measure are normally taken at a height of 1,3 m above the ground. However, there will inevitably be problems trying to evaluate this species. How are we supposed to deal with a tree with several trunks or grows big branches close to the ground?
Obviously, wrapping the whole ensemble in measuring tape at chest height will get you grotesque results. According to the rules for champion trees, you need to find the «waist» – the slimmest part of the trunk before it divides into several branches. Trees that divide below chest height (1,3 m) cannot be taken into consideration, a rule that is sometimes ignored.
The leaves are comparatively small. Their long petioles contain a latex like those of a Norway maple, and the five lobes are beautifully rounded – they even are ciliate (take a magnifying glass). Personally I find them really pretty, especially in autumn when they turn a glorious golden yellow (even red if you are very lucky). They maintain the colour a long time before turning brown and finally falling.
The flowers on the other hand, coming out at the end of April/ the beginning of May, are discrete: The blossoms show the same light green the leaves have in spring. Potentially they are androgynous, but in fact one of the two sexes in each flower is usually too underdeveloped to function. Sometimes even the whole tree is either male or female rather than mixed.
The fruit – those typical, paired wingnutlets, and lots of them – ripen in autumn, but much later than those of the Norway maple. Unlike the fruit of the other native maple species, the two wings of each pair do not form a right angle, but diverge into a horizontal line. Many of them stay in put all winter before the wind carries them away. Not far away though – only a storm could take them much further than 50 m from their mother tree.
Like every other maple species, the field maple has been classified into the soapberry familiy a few years ago.
According to the Red List, it is endangered in parts of Germany. In the course of a huge national project, set up to register and preserve rare tree species and finished in 2013, 1.3 million field maple trees were identified and mapped (see report on www.baum-des-jahres.de). The most important result of the study: There are many wild trees left but often they are in so small groups that without care they will not survive for long.
Until recently field maple was prospering in low and medium forests because it shoots from stump vigorously. Today you hardly find field maple trees in a forest any more except perhaps around the edges or underneath light-transmissive old oaks and birches. It feels most at home in hedges or shrubberies among hazel bushes, cornel and sour cherry trees – here it can outgrow the bushes and gets plenty of light.
The field maple is reckoned among the steppe trees and dry forests. It resists drought periods with the help of its small, lobed, hairy leaves whose surfaces are sealed by a matt-finished wax. Suberized ribs protect the young branches; small wood vessels secure the water transport.
Field maple trees host birds, insects and fungi – occasionally you will find root rot, but the species is less prone to fungal attacks than Norway or sycamore maple. The leaves feed a series of caterpillars of different butterfly species. They do little harm to the tree, nor do the bull- and hawfinches which may eat the buds and seeds. Game animals and the mildew infections that occur regularly in the summer can cause more serious damage.
In cities and along streets field maple has only just begun its career: Due to its small size, it can be planted even in comparatively narrow streets and small gardens. Field maple resists salt, immission, dense soil, heat, intense sunlight and drought better than many other species. I have come across many trees in the central reserve of motorways – they must be real survivors! Field maple can even be grown in pots, which is useful in pedestrian zones or roof gardens.
Field maple is also favoured in hedges not only because of its small leaves but also because it is easy to trim, e.g. into tree sculptures and mazes. Generally, it is very popular in gardening and landscaping – and this raises hope.
And there is more: It is the best indigenous species for growing bonsai trees (to keep its silhouette compact and the leaves small, grow it in full sunshine.) Field maple leaves are much appreciated forage to this day. The tree probably received its second German name «Maßholder» (measure holder) for its size – we could interpret it as «little tree».
It happens, of course, that maple trees are called field maple simply because they are standing on the edge of a field. I was called to look at several examples pointed out to me as particularly gorgeous – and when I got there I found that indeed they were. However, they were not field maple, but Norway or sycamore maple trees.
For additional information, please visit www.baum-des-jahres.de and www.holzgewaechse.de (in German).
Translation by Wiebke Roloff, Berlin/D.