Oxalis stricta, commonly known as upright yellow wood sorrel or sourgrass, is an herbaceous perennial plant in the family Oxalidaceae. It is native to North America but has naturalized in many temperate regions globally, often appearing in gardens, agricultural fields, and disturbed urban habitats. The genus name Oxalis is derived from the Greek oxys, meaning "sharp" or "sour," a direct reference to the plant’s high concentration of oxalic acid, which imparts a distinctively tart, lemony flavor to the leaves. The species epithet stricta is Latin for "upright" or "straight," describing its growth habit compared to other prostrate Oxalis species. Historically, the plant was a familiar forage item, valued by indigenous North American populations as a quick, refreshing snack and a source of Vitamin C.

The plant is characterized by its trifoliate, heart-shaped leaflets that fold down at night or under high-stress conditions (a phenomenon known as nyctinasty). It produces small, vibrant yellow, five-petaled flowers that bloom throughout the growing season. Perhaps its most striking botanical feature is its explosive seed dispersal mechanism; it produces elongated, capsule-like fruits that, when mature and touched, forcefully eject seeds over significant distances. *Oxalis stricta* is a highly resilient colonizer, capable of thriving in varied light conditions and soil types, though it prefers well-draining, disturbed sites where it can compete effectively with grasses and other low-growing vegetation.

The entire aerial part of the plant—leaves, flowers, and immature green seed pods—is edible. In contemporary foraging and small-scale culinary applications, it is used as a fresh, acidic garnish, a salad green, or an ingredient in dressings to provide a natural "lemon" accent without the need for citrus. Because of its intense tartness, it is rarely eaten in large quantities as a main vegetable but is instead utilized as a flavor-enhancing botanical. The immature green seed pods have a unique, crisp texture and a sharp flavor, occasionally utilized as a substitute for capers. However, due to its high concentration of soluble oxalates, it should be consumed in moderation, especially by individuals prone to kidney stones.

Nutritionally, wood sorrel is notable for its high content of Vitamin C (ascorbic acid) and various minerals, including potassium and iron. Its primary biochemical profile is defined by oxalic acid and its salts, such as calcium oxalate. While these compounds define its sharp sensory profile, they also act as a defense mechanism against herbivory. The plant also contains a variety of flavonoids and phenolic acids, which contribute to its potential antioxidant activities. In traditional herbalism, it has been used to treat mild fever and nausea, though its culinary utility as a seasonal botanical remains its most enduring historical role.