|The Cultivar 'Double O' is a deciduous, upright male tree, thorny when young, becoming less so as it matures. Leaves are pointed and dark green in color. They turn yellow in autumn. In early summer, dense, spherical-shaped tiny yellow-green flowers appear. Grow in a shrub border, as specimens, or as a windbreak. Growth in full sun and in moderately fertile, well-drained soil produces best results.