Acer negundo L. Box Elder or Ash-leaved Maple Native to a large area of east and central N. America, where it grows on swamp and streamsides. Box Elder has provided a source of sugar, or maple syrup, in the past but it is now more important as an ornamental tree both in Europe and in western N. America. Height to 12-15m (40-50ft). Male and female flowers are produced on different trees in April. Males are the dense red tassels, females the drooping green clusters. Keys have wings 3-3.7cm (1¼in) long. Leaves have 5 leaflets, arranged like an ash leaf, but may have only 3 leaflets. Autumn colour is clear yellow. Z2.