The rootstock is variously described as an elongated corm or a rhizome. Plants vary in height from about 7 cm (2.8 in) in the case of T. pusilla to 1.6 m (5.2 ft) in the case of T. spathata subsp. sincorana. Linear to lanceolate leaves grow from the base of the plant. Most species have flowers in some shade of yellow.