Native to the New World from southern Canada south to northern Argentina.
The leaves are long, thin and bladelike to lanceolate, from 3–45 cm long. The flowers are white, pink or purple but most commonly bright blue, with three petals and six yellow anthers. The sap is mucilaginous and clear.
A number of the species flower in the morning and when the sun shines on the flowers in the afternoon they close up, but the flowers can remain open on cloudy days until evening. Other names used for various species include Spider-lily, Cradle-lily, Oyster-plant and Flowering Inch Plant.
The cells of the stamen hairs of some Tradescantia are colored blue, but when exposed to sources of ionizing radiation such as gamma rays, the cells mutate and change color to pink; they are one of the few tissues known to serve as an effective bioassay for ambient radiation levels.
The generic name honours the English naturalists John Tradescant the Elder (ca. 1570-1638) and John Tradescant the Younger (1608-1662).