This tree is 40-80' at maturity, forming either single or multiple trunks and a relatively open ovoid crown on each trunk. Trunk bark is mottled light and dark gray; it has weak furrows and ridges that are irregular and fragmented. Branch bark is light gray with abundant lenticels (air pores), while young shoots are yellowish brown to green, relatively stout, and usually glabrous (sometimes temporarily pubescent). Alternate compound leaves about 1-3' long occur along the shoots; they are odd-pinnate (less often even-pinnate) with 11-35 leaflets. Individual leaflets are 3-6" long and 1-2" across; they are lanceolate with smooth margins, except near the base, where 1-2 pairs of blunt dentate teeth usually occur. The upper leaflet surface is dark green and glabrous, while the lower surface is pale to medium green and glabrous (or nearly so). The short petiolules (basal stalklets) of the leaflets are up to ½" in length. The petioles of the compound leaves are 3-6" long; their bases are swollen. Both the rachises and petioles are light green to red and glabrous (or nearly so). The crushed foliage of this tree has an odd scent, resembling a mixture of citrus and skunk-like odors. Tree-of-Heaven is dioecious, producing either all male (staminate) flowers or all female (pistillate) flowers on the same tree. These greenish yellow flowers are produced in panicles about 4-12" long. Male flowers are up to 1/3" across, consisting of a short calyx with 5 lobes, 5 narrow petals, and 10 fertile stamens. Female flowers are up to 1/3" across, consisting of a short calyx with 5 lobes, 5 narrow petals, 10 pseudo-stamens that are sterile, and 5 carpels with united styles. The male flowers, in particular, exude an unpleasant skunk-like odor. The blooming period occurs during mid- to late spring. While the male flowers wither away, the female flowers are replaced by single-seeded samaras that mature during the late summer or fall. Individual samaras are about 1½" long and 1/3" across; they are initially light green, but later become yellowish or reddish green, and finally become tan to brown. Each samara has two elongated membranous wings and a central seed; the wings are often slightly twisted. Individual seeds are about ¼" long, ovoid, and slightly flattened. The samaras are distributed by the wind or water. The root system is wide-spreading and relatively shallow; vegetative offshoots are sometimes produced from long underground runners.