Native to North America, Box elder is the most widespread of the American maples. In appearance it is unlike other maples, with leaves more like those of ash (Fraxinus), with leaflet pairs on either side of a rib, and a single leaflet at the tip. In autumn they are yellow.
Box elder trees are either male or female; the males’ flowers are small, in tight panicles, while the female trees produce long drooping flower bunches. Flowering occurs early in the spring before leaves appear, when the male trees in particular can be quite showy.
This is a fast-growing pioneer species which has been used against erosion in China, where it has become something of a weed.
At Mustila, Box elder originating from seed collecting expeditions can be seen growing at Lammastarha (Sheep pen), for example, near a stand of European white elm (Ulmus laevis).