Oregon Oxalis Redwood

Oxalis oregana (Oxalidaceae) is a low, rhizomatous perennial native to the coastal forests of western North America from the Olympic Peninsula to California and up the Columbia River Gorge. It grows just 2.5 to 4 inches tall from horizontal creeping rhizomes, forming dense carpets of three heart-shaped leaflets (1 to 4.5 cm, purplish beneath) on slender stalks (5 to 20 cm). White to light pink flowers (2 to 2.5 cm) are borne singly.

Redwood sorrel thrives in partial to full shade on humus-rich, moist soil, typical of Douglas-fir and coast redwood forest floors. It spreads by rhizomes and can be somewhat aggressive as a groundcover. The leaves are edible (rated 3 out of 5) with a sharp, tangy flavor from oxalic acid; large quantities can bind calcium and should be limited. Cooking reduces oxalic acid content. Documented problems include leaf spot and rust. Hardy in Zones 7a to 8b.