This native perennial plant is up to 4' tall and unbranched, except near the inflorescence. The central stem is strongly four-angled and hairless. The opposite leaves are up to 5' long and 1½' across. They are sessile, hairless, lanceolate or oblanceolate, and have sharply-pointed widely-spaced teeth along the margins. The inflorescence consists of tall spikes of flowers at the ends of the upper stems. A spike is up to 10' long and consists of 4 rows of densely packed horizontal flowers or their buds. The tubular flowers are white, lavender, or purplish pink, and they often have dots, fine stripes, or swirls of a slightly darker color. Each flower is about 1' long, has 2 lips, while 4 purple anthers are visible near the upper lip. This upper lip is a broad hood, while the lower lip is divided into 3 lobes the larger central one functioning as a landing pad for insects, which is accompanied by 2 smaller side lobes. The flowers have no scent. The blooming period occurs during late summer to early fall, and lasts about 1½ months. Each flower produces 4 sharply angled, dull brown seeds. The root system consists of a central taproot and rhizomes. The latter promote the spread of this plant vegetatively.