Wildflowers of the United States

Redwood Sorrel, Oregon Wood Sorrel, Oregon Oxalis - Oxalis oregana

Family: Oxalidaceae - Wood-Sorrel family

Genus Common Name: Wood Sorrel

Native Status: Native

Dicot Perennial Herb Leaves:Basal

Oxalis oregana - Redwood Sorrel, Oregon Wood Sorrel, Oregon Oxalis.
Oxalis is a large genus of around 500 to 700 species worldwide (most of the species in the family Oxalidaceae are in the Oxalis genus; the family has only 3 genera.) Identification can be difficult, and classification is changing and confusing. There are around 36 North American species, with at least one Oxalis species in every state except Alaska. The plant contains the mildly toxic oxalic acid

Oxalis oregana - Redwood Wood Sorrel - is a plant of western North America, found in Coastal Redwood and Douglas Fir forests in the Pacific coast states of the United States, and in British Columbia in Canada.

Found in:
CA, OR, WA

Distribution of Oxalis oregana in the United States and Canada:

Map courtesy of The Biota of North America Program.
Map color key
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Site: Prairie Creek Redwoods State Park, Humboldt County, CA Date: 2019-September-12	Photographer: Gerald C. Williamson Nikon D7000 Tamron SP 90MM f/2.8 AF Macro
The five petals of Oxalis oregana are white to deep pink, usually with magenta to purple veins, which can give even the white petals a pinkish hue. The petals usually have a yellow dot at their base.

Site: Prairie Creek Redwoods State Park, Humboldt County, CA Date: 2019-September-12	Photographer: Gerald C Williamson Nikon D7000
Oxalis oregana is heterostylous. I do not fully understand this phenomenon, but in this type of plant, there are two or three different types ("morphs") of a flower in a population, and a particular plant will have only one of these morphs. In each morph, the styles and stamens are different lengths, and in some manner this has the effect of preventing self-pollination or pollination of another plant of the same morph.
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Site: Prairie Creek Redwoods State Park, Humboldt County, CA Date: 2019-September-12	Photographer: Gerald C Williamson Nikon D7000
The hairy peduncle arises from the rhyzome up to nearly 10 inches, rising to a single flower. There is a pair of bracts about halfway to the flower.
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Site: Prairie Creek Redwoods State Park, Humboldt County, CA Date: 2019-September-12	Photographer: Gerald C Williamson Nikon D7000
The leaves of Redwood Sorrel are all basal, with as many as 10 clustered at the end of the rhyzome. The 3 leaflets are usually purple on their undersides. The leaflets are heart-shaped with a distinct indentation at the tip. The petiole, which may be nearly 8 inches long, and leaf surfaces are usually hairy.
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Site: Humboldt State Park, Humboldt County, CA Date: 2019-September-14	Photographer: Gerald C Williamson Samsung S8
Colonies of Oxalis oregana can be quite extensive, making an effective groundcover. The flowers peek above the leaves.
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References used for identification and information:

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Oxalis oregana initially published on USWildflowers.com 2019-11-29; Updated 2019-11-29

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Code Update 20230302