Yellow Wood-Sorrel

Oxalis europea (fontana?) and Oxalis stricta

There seem to be two almost identical species of Yellow Wood-Sorrel (sharing the same common name), but the classification and nomenclature is still debated among experts so they are both treated together here.  There are hundreds of species in the genus Oxalis worldwide.

Yellow Wood-Sorrel is a native perennial of which both species have alternate leaves consisting of three inverted heart-shaped leaflets (i.e., the leaflets join at the point of the heart, and the indentation of the heart is at the tip of each leaflet). These sour-tasting leaves are about 1 inch aross and each leaflet is sharply divided in the center; when in shade, the leaflets tend to fold up. The leaf stems can be several inches long; in O. europea stems may be smooth or covered with spreading white hairs (see photo at left); in O. stricta stems have short hairs that are appressed to the stem.  Flowers of both species are small, about 3/8 to 1/2 inch across, with five yellow petals, that are held in a small umbel on stems rising from leaf axils. The best diagnostic feature are the cylinder-shaped seed capsules that replace the flowers; in O. europea these ascend from the stem holding the umbel (see photo at left, far right), whereas in O stricta the seed capsules are sharply reflexed, descending from the stem holding the umbel.

1 foot, sun - partial shade.

Spring-Autumn (April-October).

O. stricta.

24 May 2020.

Yellow Wood-Sorrel (O.europea), 27 September 2020.