upright yellow woodsorrel

Upright yellow woodsorrel is an annual or short-lived perennial plant that has short rhizomes, but never has bulbs. The alternate leaves of this plant are divided into three distinctively heart-shaped leaflets (a typical trait of other species of Oxalis) that can grow up to 2 cm (0.79 in) wide. These leaves curl up at night (exhibiting nyctinasty), and open in the day to perform photosynthesis. The flowers of the plant are hermaphroditic, blooming from July to October. The mature seed capsules open explosively when disturbed (a very similar trait to that of the mature seed capsules or fruits of plants found in the genus Impatiens) and can disperse seeds up to 4 m (13 ft) away. Erect when young, this plant later becomes decumbent as it lies down, and branches regularly. It is not to be confused with similar plants in the same genus which are also often referred to as "yellow woodsorrel".

O. stricta is native to North America and East Asia and has been introduced elsewhere, especially in Europe. It was not documented in Michigan before the 1890s. It tends to grow in woodlands, meadows, and in disturbed areas as both a perennial and annual. and generally requires dry or moist, alkaline soils, preferring sandy and loamy dirt to grow in. It requires well-drained soil and can grow in nutritionally poor grounds. Commonly considered a weed of gardens, fields, and lawns, it grows in full sun or shade.

All parts of the plant are edible, with a distinct tangy flavor (common to all plants in the genus Oxalis). The leaves have a similar taste to lemons. Oxalis stricta is often eaten while hiking or camping. However, it should only be eaten in small quantities, since oxalic acid is an antinutrient and can inhibit the body's absorption of calcium. The sour flavor is eliminated when the plant is cooked.

The leaves and flowers of the plant are sometimes added to salads for decoration and flavoring. These can also be chewed raw (along with other parts of the plant, but not the root) as a thirst-quencher. The green pods are pleasant raw, having a juicy crisp texture and a tartness similar to rhubarb in flavor. The leaves can be used to make a flavored drink that is similar in taste to lemonade, and the whole plant can be brewed as herbal tea that has an aroma somewhat like that of cooked green beans. The juices of the plant have been extracted from its greens as a substitute for common vinegar.

Oxalis stricta contains large amounts of vitamin C, and has been used to treat scurvy. A poultice of the plant has been used to treat swellings.