Acer negundo, also known as the box elder, is a species of maple in the family Sapindaceae, native to North America. It is a fast-growing, short-lived tree with opposite, ash-like compound leaves. It is sometimes considered a weedy or invasive species, and has been naturalized throughout much of the world. It grows up to 10 to 25 metres (35 to 80 feet) tall, with a trunk diameter of 30 to 50 centimetres (12 to 20 inches). Male and female flowers appear on separate plants, with flowers on male plants generally appearing in clusters of four and flowers on female plants appearing as a raceme. These flowers of a female A. negundo plant were photographed in Keila, Estonia.Photograph credit: Ivar Leidus