Celtis occidentalis - Western hackberry, Common hackberry. Origin: Central and Eastern North America. Imported in Europe in 1656. Tree with a wide, irregular crown, 10-15 m high. The bark on older trees is greyishbrown, with characteristic lengthwise winding corky fissures and wart-like protrusions. Long, thin twigs, initially hairy. Thin, egg-round leaf, of which only the upper half is serrated, the lower half has a straight margin. Green, unisexual flowers in May. Pea-green, round fruits, later turning brown. Park tree, but certainly also an attractive avenue and street tree in wider street and avenue profiles. The low crown does require space, as well as timely pruning to ensure a higher stem height. In Central and Southern European cities, often a valuable avenue tree.