Oxalis oregana

Oxalis oregana, also known as Redwood sorrel, is a species of the wood sorrel family, Oxalidaceae, native to moist Douglas-fir and Coast Redwood forests of western North America from southwestern British Columbia, Washington, Oregon, and California. This attractive groundcover can spread vigorously when planted in favorable conditions.

It is a short herbaceous perennial plant with erect flowering stems 5-15 cm tall. The three leaflets are heart-shaped, 1-4.5 cm long on 5-20 cm stalks. The inflorescence is 2.4-4 cm in diameter, white to pink with five petals and sepals. The hairy five-chambered seed capsules are egg-shaped, 7-9 mm long; seeds are almond shaped.

Oregon oxalis photosynthesizes at relatively low levels of ambient light (1/200th of full sunlight). When direct sunlight strikes the leaves they fold downwards; when shade returns, the leaves reopen. This process only takes a few minutes and the movement is observable to the eye.

The tangy leaves of Oregon oxalis were eaten by Native Americans, probably in small quantities, since they contain mildly toxic oxalic acid (hence the genus name).