Oxalis stricta aka Yellow Wood Sorrel

Oxalis stricta is known as common yellow woodsorrel. It belongs to the wood sorrel family, Oxalidaceae. Its native range includes North America and parts of East Asia. Kew lists central and eastern China through northern and central Japan. It grows in woods, meadows, and ground disturbed by people. It also grows in old fields and along roads. Poor soil does not stop its growth.

This small herb can live as an annual or perennial. NC State gives heights of 0.17–1 foot [0.05–0.3 metres]. Its green leaves have three heart-shaped leaflets with smooth edges. The leaves fold at night and open again each morning. Its small flowers are bright yellow, with four or five petals. NC State records blooms from spring through fall. PFAF places the main bloom from midsummer into fall. The cylindrical seed pods burst when ripe. They can throw seeds up to 16 feet [4.9 metres].

Full sun suits this plant, though it also tolerates partial shade. It prefers sandy or loamy soil that drains well. NC State lists a preference for alkaline soil. Soil can be dry to moist. PFAF reports easy growth in warm, dry sites with sandy soil. Growth is fast, with the strongest growth in spring or fall. Plants may remain present all year in warm climates. New plants grow from seeds, rhizomes, and stolons.

This species can fit a native garden, but it spreads readily. It can become a stubborn weed in lawns and beds. Roots and creeping stems make established patches hard to clear. Seeds need light to sprout, so mulch can limit seedlings. Mulch does not stop new growth from root pieces. NC State reports that plants can host whiteflies and mites. Boiling the whole plant yields a yellow to orange dye. PFAF records past use for fevers, nausea, cramps, and swellings.

Leaves, stems, flowers, and young seed pods have food uses. PFAF also lists the root as edible, without further detail. The leaves can make a drink with a lemon-like taste. Oxalic acid gives the plant its sour taste. Eat only small amounts, since large amounts can cause harm. People prone to kidney stones or gout should take care. NC State flags risks to people, cats, dogs, and horses. It rates the plant's poison severity as low.