Commelina is genus in Commelinaceae family with many annual or perennial species with fibrous or rarely tuberous or rhizomatous roots. They are known by common names of dayflowers or widow's tears because their flowers are fleeting.
Commelina coelestis Willd. is a tuberous species distributed from Mexico to Central America where it is found in moist fields or open forest from medium to high elevations. It has small clusters of blue flowers with three rounded petals and yellow stamens and flowers late summer into autumn. Blooming the first year from seed it is fairly tolerant of different conditions, but prefers a well drained soil and is deciduous in winter. It needs to be protected from slugs. The tubers are apparently edible, but bland. Photos from Janos Agoston.
Commelina tuberosa L. is another tuberous species native to Mexico where it grows in moist fields and open forests. Some sources include Commelina coelestis, Commelina dianthifolia, and Commelina elliptica in this species, but other sources consider them separate species. Commelina tuberosa blooms the first year from seed and has a succession of bright blue flowers emerging one per day from a clasped like sheath. Flowering in summer and deciduous in winter, the flowers open in the morning and close in the afternoon. The tubers are apparently edible, but bland. The last photo shows the opening fruit and seeds. Photos from Mary Sue Ittner.