Other common names for this species are Red Sorrel, Field Sorrel, and Common Sorrel. Sometimes the leaves are added in small amounts to salads and other culinary dishes to provide a sour taste. However, they contain significant amounts of oxalic acid, which can be toxic to the kidneys if a sufficiently large quantity of leaves is eaten. Sheep Sorrel closely resembles in appearance its native counterpart, Rumex hastulatus (Wild Sorrel). Wild Sorrel occurs in only two counties in SW Illinois and is state-listed as endangered. It differs from Sheep Sorrel primarily by its inner sepals – they become winged and heart-shaped with maturity, fully enclosing each achene. The root system of Wild Sorrel consists of a taproot; it may form clumps of plants through short rootstocks, but doesn't create new plants from long spreading rhizomes. Another species that is rarely encountered in the wild is Rumex acetosa (Garden Sorrel). This introduced species is a bigger plant than Sheep Sorrel. Garden Sorrel has sagittate leaves (with basal lobes that are downward pointing, rather than spreading), and its cauline leaves clasp the flowering stalks.