Redwood Sorrel

Oxalis smalliana is a short, herbaceous perennial with erect flowering stems. The three leaflets are heart-shaped with purplish undersides. Like O. oregana, the leaves fold downwards when direct sunlight strikes them and reopen when shade returns, a movement observable to the eye. The flowers of O. smalliana are generally larger than those of O. oregana, with the petals measuring at least 15 mm in length. The flowers range in color from white to pink, purple, or blue, in contrast to O. oregana which has only white flowers. The plant spreads by scaly rhizomes and can form extensive patches in favorable conditions. The seed capsules are egg-shaped and hairy.

Oxalis smalliana has a southern distribution ranging from Monterey County, California to Curry County, Oregon. It grows primarily in the understory of coast redwood forests and other moist, shaded environments. In northwestern California and southwestern Oregon in the Klamath Range, its range overlaps with O. oregana, with both species sometimes found growing together in sympatric populations.

In areas where O. smalliana and O. oregana coexist, they show different flowering phenology, with white-flowered O. oregana reaching peak flowering approximately one month later than purple-flowered O. smalliana. This temporal separation in flowering may contribute to reproductive isolation between the two species.

Like O. oregana, the leaves of O. smalliana are edible but contain oxalic acid, which is mildly toxic in large quantities. They are safe to eat in small amounts for those with no oxalate-related conditions. Oxalis smalliana can be used as a groundcover in cultivated landscapes under shady and cool conditions.