Common Yellow Wood-Sorrel

<em>Oxalis dillenii</em>, the common yellow wood sorrel or slender yellow wood sorrel, is a small annual to short-lived perennial herbaceous plant in the family Oxalidaceae. It is native to eastern North America and has been introduced to many parts of Europe, Asia, and other temperate regions, where it occurs as a weed of cultivated ground, roadsides, waste places, lawns, and disturbed habitats. The plant typically grows 10–35 cm tall and produces trifoliate leaves with three notched, heart-shaped leaflets that fold downward in darkness or heat. Small bright yellow flowers with five petals are produced from spring through autumn. The cylindrical seed pods eject seeds forcibly at maturity. Biological traits such as average lifespan and body measurements remain poorly documented in consolidated scientific literature. Like other Oxalis species, <em>Oxalis dillenii</em> contains oxalic acid, giving leaves a sour taste and making them mildly toxic when consumed in large quantities. The plant provides nectar for small generalist pollinators. It has not been formally evaluated for IUCN conservation status but is considered common and widespread with no conservation concerns across its introduced and native ranges.