Wood Sorrel

Wood sorrel is a small creeping perennial of the family Oxalidaceae, found in woods and shady places across most of Europe and northern and central Asia. Wikipedia says its leaves fold and its flowers close at night or in the rain, and that the name acetosella refers to its sour taste. It records that an English botanist in 1830 claimed it to be the true shamrock, though the usual view is that the shamrock is a clover. Kynes calls it earth, with Taurus and Venus, and links it to elves and faeries. She lists healing, peace, prosperity and protection, with a leaf in the shoe to see faeries and a leaf carried for luck. Wikipedia says the leaves are high in oxalic acid, noted in the safety notes.