Creeping woodsorrel (Oxalis corniculata)
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Creeping woodsorrel is a low growing perennial broadleaf plant with shamrock-like leaves. It grows throughout California to 8200 feet (2500 m) and inhabits agricultural land, greenhouse and other disturbed sites. It is related to, and closely resembles Bermuda buttercup (buttercup oxalis). Both species contain variable levels of oxalate compounds that when eaten in quantity, can cause death in livestock. Bermuda buttercup prefers shady conditions but can grow in sun.
Yards, gardens, turf, landscaped areas, urban places, orchards, vineyards, fields, and agricultural crops, and nursery and greenhouse grounds and containers.
The cotyledons (seed leaves) are oval to egg shaped and hairless, except for minute hairs along the edges that point upward. They range from 1/12 to 1/5 of an inch (2–5 mm) long and 1/25 to 1/10 of an inch (1–2.5 mm) wide. Leaves are alternate to one another along the stem. The first leaf has three leaflets that are broadly heart shaped.
The mature plant is low growing. Its creeping, aboveground horizontal stems grow to about 12 inches (30 cm) long and root at the stem joints (node) allowing it to invade new areas. Leaves resemble those of clover and range from green to dark purple-tinged. Hairless to sparsely hairy, leaves are fully subdivided (compound), each consisting of three heart-shaped leaflets that are 1/4 to 2/5 of an inch (0.6–1 cm) long and 1/6 to 1 inch (0.4–2.5 cm) wide. In comparison to the leaves, leaf stalks are long, almost 3 inches (7 cm) in length. Leaves are alternate to one another along the stem and usually fold downward at midday and at night. Leave are gernally green but a variant with purplish leaves is also common.
Flowers are present almost year-round. Two to five yellow flowers form a cluster that develops where leaf stalks and stem meet (leaf axil). The small flowers have five yellow petals. Creeping woodsorrel has less upright growth and less showy flowers than Bermuda buttercup, a similar looking plant.
Fruit consist of green cylindrical capsules (similar to pods) that either have five weak lobes or are angled and attach to stalks that stand erect or curve downward. Each capsule ranges from 1/4 to 1 inch (0.6–2.8 cm) long and contains a few to numerous seeds.
Seeds are egg shaped, flat, brown, have transverse ridges, and are roughly 1/16 of an inch (1.6 mm) long. When seeds mature, capsules open explosively, often spreading seeds 10 feet (300 cm) or more.
Seeds and creeping aboveground horizontal stems that root at stem joints (nodes).
Related or similar plants
- Bermuda buttercup (buttercup oxalis), Oxalis pes-caprae
- Black medic, Medicago lupulina
- California burclover, Medicago polymorpha
- Strawberry clover, Trifolium fragiferum
- White clover, Trifolium repens
- Broadleaf ID illustration
- Calflora's distribution map
- For gardens and landscapes: UC IPM Creeping Woodsorrel and Bermuda Buttercup Pest Note
- For agriculture: UC IPM Pest Management Guidelines