Rumex scutatus

Rumex scutatus is a plant in the buckwheat family, used as a culinary herb. Its common names include French sorrel, buckler sorrel, shield-leaf sorrel, and sometimes the culinary name "green-sauce".
As a culinary herb, it is used in salads, soups, and sauces. French sorrel tastes tart from its oxalic acid content, with a hint of lemon. Later in the season, it can be bitter.
French sorrel is hardy in most regions, tolerating frost, full sun and short dry spells. It grows quickly to a clump up to in diameter, with long leaves up to wide. It is sometimes preferred for culinary uses to Rumex acetosa, garden sorrel.