Leaves are opposite (2 leaves per node), although sometimes are alternate or whorled; slender, narrow and elongated. Multiple, stout, purple-tinged stems emerge from a single root crown. The stems (mostly hairless) can reach 5 feet in height and often have a deep, rich maroon-colored foliage in the fall.
Sweetly scented flowers are arranged in small, rounded clusters near the top of stem; 10-20 flowers per cluster. The exserted (protruding) horn is much taller than the oblong hood and curves away toward the flower center.