This perennial wildflower is 3-7' tall. It has a central stem that is unbranched below, becoming branched above. The stems are are usually purple, more or less terete, and either glabrous or minutely and sparingly pubescent. The alternate leaves are ternately compound; they are up to 2' long and across, becoming smaller as they ascend the stems. The lower leaves have long petioles, while the upper leaves have either short petioles or they are sessile. Individual leaflets are ¾-2" long and ½-1½" across; they are oblong-ovate or oblong-obovate in shape, while their margins are smooth and sometimes revolute (rolled downward). Individual leaflets usually have 2-3 lobes along their outer margins, but sometimes they are unlobed. The upper leaflet surface is medium green and glabrous, while the lower surface is either light green and glabrous or light grayish green and short-pubescent. The leaflets usually have short slender petiolules (basal stalklets), but sometimes the lateral leaflets in a group of 3 are sessile. The petioles, petiolules, and rachises are usually purple and glabrous, but sometimes they are light green, especially when a plant is growing in shade. Because Purple Meadow Rue is dioecious, individual plants produce either all male (staminate) flowers or all female (pistillate) flowers. Regardless of gender, the central stem of a plant terminates in a panicle of flowers about ¾-2' long and about one-half as much across. In addition, smaller panicles of flowers are often produced from the axils of upper leaves. There is a tendency for female plants to produce smaller panicles than male plants. The branches of a panicle are usually purple and glabrous. Individual male flowers are about 1/3" (8 mm.) long, consisting of 4-5 deciduous sepals and up to 15 stamens; there are no petals. The filaments of the stamens are slender and white, while the anthers are pale yellow. Individual female flowers are about 1/3 (8 mm.) long, consisting of 4-5 deciduous sepals and up to 15 pistils; there are no petals. The pistils are light green. The blooming period occurs from early to mid-summer for about 2-3 weeks. The flowers are cross-pollinated by the wind. Afterwards, the female flowers are replaced by spindle-shaped achenes that turn brown at maturity. Each achene has a beak at its apex and 4-6 raised ribs along its sides. The root system is fibrous and rhizomatous. Clonal offsets are sometimes produced from the rhizomes.