This shrub is 4-25' tall, branching abundantly. The bark of trunk and larger branches is gray to brown and fairly smooth, although on old large shrubs it can become shallowly furrowed with a wrinkled appearance. Twigs are brown and glabrous, while young shoots are light green and nearly glabrous to pubescent. Pairs of stout prickles up to 1/3' long are scattered along the branches, twigs and shoots; these spines are somewhat flattened and curved. Alternate compound leaves about 6-12' long develop along the twigs and young shoots; they are odd-pinnate with 5-11 leaflets. Individual leaflets are 1½-3¼' long and ½-1½' across; they are lanceolate-oblong to ovate-oblong with margins that are smooth to crenulate (fine rounded teeth). The upper surface of mature leaflets is medium green, minutely glandular, and glabrous, while the lower surface is pale green and short-pubescent to nearly glabrous; in the latter case, fine hairs are restricted to the major veins. Newly emerged leaflets are more hairy than mature leaflets. The lateral leaflets are sessile or nearly so, while the terminal leaflets have slender petiolules (basal stalklets) that are less than ½' long. The light green petioles (basal stalks) and rachises of the compound leaves are hairy while young, but become more glabrous with age; they have scattered small prickles along their undersides. Prickly Ash is almost always dioecious, producing male (staminate) and female (pistillate) flowers on separate shrubs. These flowers are arranged in small axillary clusters (cymes) along the branches of the preceding year. Individual male flowers are a little less than ¼' across, consisting of 4-5 erect petals and 4-5 stamens; there is no calyx. The petals of male flowers are yellowish green to orange and oblong in shape. Individual female flowers are about ¼' across, consisting of 4-5 erect petals and 2-5 separate pistils; there is no calyx. The petals of female flowers are also yellowish green to orange and oblong in shape. The ovaries of the pistils are glossy green and ovoid in shape; their elongated styles tend to converge at their tips. The blooming period occurs during mid- to late spring before the leaves develop. Afterwards, the female flowers are replaced by berry-like follicles (fruits that open along one-side) about 1/3' long that are ovoid-globoid in shape with a pitted surface. As the follicles mature, they change from green to red to brown, eventually splitting open to expose shiny black seeds with oily surfaces. Each follicle contains 1-2 seeds. Both the crushed foliage and fruits are highly aromatic, somewhat resembling the fragrance of lemon peels. The root system produces underground runners, from which clonal offsets are produced. This shrub often forms clonal colonies of varying size.