This perennial native plant is 3-6' tall, branching occasionally. The stout stems are smooth and hairless; they can be green or purple, sometimes with purplish lines or spots. The lower portion of the central stem is hollow. The compound leaves are odd-pinnate or double odd-pinnate; they alternate along the stems. The lower compound leaves are up to 1½' long and ¾' across; the upper compound leaves are much smaller. Each division of a compound leaf often has only 3 leaflets, but sometimes there are many more. The petiole of each compound leaf forms a sheath around the stem. The hairless leaflets are up to 4" long and 1¼" across. They are narrowly ovate with a wedge-shaped bottom, and are strongly serrated, often folding upward along the length of the central vein. The radial veins spread to the notches, rather than the tips, of the teeth along the leaf margin. The upper stems occasionally produce compound umbels of small white flowers. These compound umbels are up to 6" across and consist of 10-20 umbellets. An umbellet has about 12-15 flowers. Each flower is about 1/8" across, consisting of 5 white petals, 5 white stamens, and a divided style. The little petals are constricted at the base, and have notched tips. The blooming period is mid-summer, and lasts about a month. The flowers have a slight fragrance that is sometimes detectable. Each flower is replaced by a small 3-angled fruit. The root system consists of several fleshy roots at the base of the plant; they are ovoid or oblong in shape. These fleshy roots are exceptionally poisonous; the stems and foliage are somewhat less poisonous. This plant spreads by reseeding itself into adjacent areas.