Celtis occidentalis L. Hackberry or Nettle Tree Native to eastern N. America, planted as a shade or ornamental tree in Mississippi, eastern States and Europe. Height to 9-12m (30-40ft). Flowers open in May, the females developing into fruit which is about 0.8cm (1/3 in) across similar to fruit of C. laevigata, orange red ripening to dark purple. Leaves are downy on the main vein beneath. Bark is grey with distinctive warty growths. Zone 2.