The garden sorrel is also known as spinach dock, common sorrel or sorrel. Its scientific name is Rumex acetosa. It's both a wild plant that grows on grasslands and a cultivated one that grows in gardens or in containers indoors. Sorrel is native to Europe and Asia but has been introduced to North America.
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The flowering stems of garden sorrel are tall and bear small red flowers. In places where sorrel grows abundantly, a field may look red during the flowering season due to the presence of numerous sorrels in bloom.
Sorrel leaves are used in many ways. They are eaten raw in salads, steamed or boiled to use as a vegetable and pureed to make a soup or a sauce. The leaves are also added to stews, pies, mashed potatoes and sandwiches. They are a great seasoning for egg, fish, poultry and meat dishes.
Ivar Leidus, CC BY-SA 3.0 License
Oxalic acid isn't poisonous in plants such as sorrel. However, questions have been raised about whether people with a tendency to develop calcium oxalate kidney stones should eat foods high in oxalic acid or a closely related chemical called oxalate. (Oxalic acid and oxalate are interconvertible). The question isn't easy to answer, because foods high in oxalic acid or oxalate don't necessarily increase the level of oxalate in the body or urine. Another problem is that other factors in the diet beside the ingestion of foods high in oxalic acid are known to affect the body's oxalate level.
Steaming or boiling leaves reduces their oxalic acid content. Younger leaves generally have less oxalic acid than older ones. Of course, a person should follow their doctor's advice if he or she recommends that they reduce the amount of oxalic acid and oxalate that they eat. For many people, though, sorrel leaves in small to moderate quantities are a lovely addition to the diet.