Box elder, boxelder maple, ash-leaved maple, maple ash (Eng), negundo, arce de hoja de fresno (Spa), negundo (Cat), negundo astigar (Baq), bordo-negundo (Por).
“His face was as well lined as the veins in maple wood, and was more or less the same colour.”
‘Animal dreams’, Barbara Kingsolver
Fast-growing deciduous tree that can be 20 m tall. Its bark is smooth, greyish and cracks with age. Its leaves are opposite and it is the only maple in this guide that has compound leaves; there are 3 or 5 oblong toothed leaflets that resemble ash leaves, hence some of its common names, although sometimes they are irregular with pointed lobes. The leaves do not secrete latex when cut. It flowers in spring before the leaves develop. As it is wind pollinated, the flowers have no petals and bloom in hanging groups; male and female flowers are borne on different plants. Its fruits are samaras, or keys, i.e., the seed has a 2 cm long membranous wing that allows it to be dispersed by the wind. They form in pairs with a 60° v-shaped angle between them.
In its natural habitat this plant is associated with watercourses, reservoirs, lakes, and wetland areas. As an ornamental and shade tree it is very resistant to pollution and severe pruning, and can grow in all soil types, even when they are nutrient-poor and badly drained. When it becomes established in the wild it mainly colonises altered areas, roadsides, wasteland and riverbanks, from sea level up to 1200 m.
The boxelder maple is a native of central and northern America, but has it been so widely grown as an ornamental that it has become naturalised in many parts of the world. On the Iberian Peninsula this tree is cultivated in all the provinces, is established in the wild in many places, and is included in the Atlas of invasive alien plants of Spain.