Yellow dock, also known as field sorrel and curly dock, is a hardy, perennial that is native to Europe and now naturalized in much of North America. The large, curled leaves are sometimes cooked as a vegetable to reduce their bitter flavor. However, the herb is most commonly cultivated or harvested for its long, spindle-shaped, yellow taproot, which contains oxalate compounds, as well as emodin and other anthraquinones. Dried yellow dock root is typically made into tinctures or extracts, while the powdered herb is used to produce topical preparations.