A beautiful North American perennial, 1-2 ft. high, with narrow purple-veined leaves and violet-blue flowers on branching stems in summer. There are several varieties, alba, atropurpurea, atroviolacea, coerulea, purpurea, rubra, etc., differing in colour according to the names. They grow in ordinary soil, and are increased by division. A closely related plant is Commelina coelestis, from Mexico, with tuberous roots, oblong lance-shaped leaves, and bright-blue flowers; there is also a white variety.