Rumex hymenosepalus (USA)

Rumex hymenosepalus
, commonly known as canaigre, ganagra, wild rhubarb, Arizona dock, and tanner's dock,[2] is a perennial flowering plant which is native to the western United States and northern Mexico.

It has been cultivated in the southwestern United States for the roots, a good source of tannin, which is used in leather tanning. It also yields a yellow dye.[3]

(From Wikipedia on 13.5.14)

Rumex hymenosepalus, photographed from Caifornia
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