Oxalis corniculata (creeping woodsorrel).

Abstract The herbaceous plant O. corniculata is commonly described as being widely naturalized and its origins obscure. The species has many weedy characteristics, being readily self-pollinated, producing copious seeds in a short time, and being capable of growing rapidly in open places. Its spread appears phenomenal. It is considered a cosmopolitan weed of tropical and temperature zones and it probably occurs in most countries in the world, although it may not yet have been reported from all. It occurs in gardens, lawns, arable land and pastures. In Canada it is especially prevalent as a weed of glasshouses. It is a known weed of many crops across the world, from tea in Sri Lanka to rice in Japan. Its spread has been partly accidental and partly deliberate, since its oxalic acid-containing leaves have long been used for culinary purposes, and for their medicinal and herbal value.