Oxalis stricta L.
Leaves are divided into three heart-shaped leaflets. At night, or if the plant is under stress such as direct sun or during storms, the leaves fold up. Delicate, 5 petalled flowers grow in clusters. When disturbed, mature seed capsules open explosively, ejecting seed up to 4 m. Circumpolar, originated in North America. Spreads readily; can be weedy.
Everywhere in dry conditions.
Birds: pine grosbeak, juncos, eat the seed.
All parts are edible. May be used sparingly in salads; has a sour taste. High in vitamin C.