About Marah watsonii (Cogn.) Greene
Marah watsonii, commonly known as taw manroot, is an uncommon species in the genus Marah that is endemic to central northern California. Its native range is bounded by the eastern coastal foothills to the west and the western foothills of the northern Sierra Nevada and Cascade ranges to the east, and extends from Lake Berryessa in the south to Lake Shasta in the north. Taw manroot grows most vigorously along streams or in washes, but can also grow successfully in drier areas, at elevations up to 1,600 meters (5,200 ft). It tolerates a wide range of soil types and acidity levels, but requires at least seasonally moist soil. Its vines can grow in conditions from full sun to heavy shade. The vines die back in summer and re-emerge in late winter. All parts of this plant have a bitter taste; this bitterness is the meaning of the genus name Marah, which originates from Hebrew. In spite of the bitter taste, the leaves of this species have been used as a vegetable. The large tuber of taw manroot can be processed to produce a soap-like extract.
