Flora of North America species comparison

The enlarged storage roots of Manihot esculenta yield a starchy staple, now much consumed in tropical regions around the world. Tapioca, a pelletized and partially hydrolyzed form of cassava starch, is the chief form of consumption in temperate regions. Multiple cultivars are known. These are generally characterized as bitter (containing cyanogenic glycosides, which must be removed before consumption) or sweet (cyanogenic glycosides absent or at low levels). A form with variegated leaves is sometimes grown for ornament. Cassava was cultivated throughout the Neotropics in pre-Columbian times. As a root crop with poor storage qualities adapted to humid regions, archeological remains are few, leading to much speculation in the literature about the origin of this important crop. Molecular data reported by K. Olsen and B. A. Schaal (1999, 2001), indicate that cultivated cassava constitutes M. esculenta subsp. esculenta, derived by artificial selection from its sole wild ancestor, M. esculenta subsp. flabellifolia (Pohl) Ciferri from the southern border of the Amazon basin. Under this classification, all North American plants belong to subsp. esculenta.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Although D. J. Rogers and S. G. Appan (1973) characterized leaf blades of Manihot subspicata as peltate, seldom are leaves unambiguously so. Typically, just the thickened margins of lateral lobes are confluent across the distal end of the petiole. Though relatively common in northern Mexico, M. subspicata is known in Texas only from the vicinity of Lake Corpus Christi (Jim Wells and Live Oak counties); whether native or introduced there is unresolved. In Mexico, M. subspicata appears to be tolerant of disturbance, frequently colonizing roadsides and similar habitats.

(Discussion copyrighted by Flora of North America; reprinted with permission.)