Mountain Woodsorrel (Oxalis oregana) is a captivating plant often found in shaded woodland environments. This article explores its botanical identity, physical characteristics, habitats, and uses.
What is Mountain Woodsorrel?
Mountain Woodsorrel (Oxalis oregana) belongs to the Oxalidaceae family. It is a perennial herbaceous plant, living for more than two years without woody stems. This plant typically forms low-lying patches, spreading through underground rhizomes. Common names like redwood sorrel or Oregon oxalis reflect its native range and habitat.
Key Identification Features
Mountain Woodsorrel is readily identifiable by its trifoliate leaves, resembling a clover with three heart-shaped leaflets. These leaflets are typically mid-green, often with a purplish tint on their undersides, and can be up to 4.5 cm long on stalks 5 to 20 cm. The leaves fold downwards in direct sunlight or at night, unfolding when shade returns.
It produces delicate, funnel-shaped flowers, typically white to rose-pink, sometimes with lavender or darker pink veins. Each flower has five petals and five sepals, measuring 13 to 20 mm in diameter. Flowers appear singly on erect stems 5 to 15 cm tall, blooming from spring through fall in many areas. The plant’s growth habit is low-growing and mat-forming groundcover.
Where Does It Grow?
Mountain Woodsorrel thrives in moist, shady forests. It is frequently found under the canopy of conifers, such as Douglas-fir and coast redwood forests, which provide the dappled sunlight or deep shade it prefers.
The plant favors moist, fertile, humus-rich, and well-drained soils. It tolerates sandy sites and clay, but consistently moist, acidic to slightly neutral conditions are ideal. Its native distribution spans western North America, from southwestern British Columbia through Washington, Oregon, and into northern California.
Edibility and Traditional Uses
Mountain Woodsorrel leaves are edible, with a distinct tart, lemony flavor due to oxalic acid. They can be consumed raw in small quantities, often added to salads for a tangy zest, or used as a flavoring in various dishes. Traditional uses include making conserves or a pie from the leaf stalks.
Moderation is advised when consuming Mountain Woodsorrel due to its oxalic acid content. Large quantities can interfere with calcium absorption and may be problematic for individuals with kidney issues, gout, or rheumatism. Cooking the leaves can help reduce oxalic acid. Historically, indigenous peoples, including the Cowlitz, Quileute, and Quinault, ate the leaves.
Ecological Role and Distinguishing Similar Species
Mountain Woodsorrel serves several ecological functions within its native woodland ecosystems. It acts as an effective groundcover, helping to stabilize soil and enrich the forest floor. Its flowers attract pollinators such as native bees, syrphid flies, and butterflies, contributing to the biodiversity of its habitat. The leaves also provide a food source for small rodents and other seed-eating wildlife.
Distinguishing Oxalis oregana from similar species like Common Woodsorrel (Oxalis acetosella) or Creeping Woodsorrel (Oxalis corniculata) involves key differences. Oxalis oregana is primarily found in western North America and consistently produces white flowers, sometimes with pinkish hues. Oxalis acetosella is found in eastern North America and Europe, also with white to pink flowers. Creeping Woodsorrel (Oxalis corniculata) often has yellow flowers and a more procumbent growth habit, rooting at nodes along its stems, and is often considered a weed in disturbed areas. Oxalis oregana typically has only one flower per stalk, while other species like Oxalis trilliifolia may have multiple flowers.