canaigre

The true tannic acids are also widely distributed; […] in roots, as in the Texas plant, a Rumex commonly known as "Cañaigre;" […]

The preparation of an extract of cañaigre for tanning is a new industry,[…]. The cañaigre extract will be used for light leather, and it is expected that a ready market can be found in England for the whole product, at very profitable prices, and the plant can be raised upon land which is practically useless for other agricultural purposes.