A herb. It loses its leaves during the winter. It grows 1.2 m high. The roots are slightly fleshy. They have a swollen tuber near the tip. The leaves are narrow and 50-70 cm long by 0.7-1 cm wide. There can be many flowers. They are small and have a scent. The flowers open during the day. They are orange or yellow. They are purplish black in bud. The fruit is a capsule. It is oval and 1.5 cm long by 0.8 cm wide.