Common Sorrel, Garden Sorrel or Sheeps Sorrel (Rumex acetosa), is often simply called Sorrel and also known as Spinach Dock or Narrow-leaved Dock. It is a perennial herb that has been cultivated for centuries as a garden herb or leaf vegetable. The leaves may be puréed in soups and sauces or added to salads; they have a flavour that is similar to kiwi fruit or sour wild strawberries. The plant's sharp taste is due to oxalic acid. In small quantities Sorrel is harmless and used widely throughout the world in cooking. It thrives best with a little manure. Red "flowers" in May at the same time as the Buttercups. This cousin of the Rumex family is not invasive, such as the Broadleaf Dock, and is palatable by livestock and horses.