Redwood Sorrel, Oregon Wood Sorrel, Oregon Oxalis - Oxalis oregana
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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:
Blue=Native; Grey=Introduced
Map from USDA Plants Database:
USDA, NRCS. 2017. The PLANTS Database (http://plants.usda.gov, 16 Jan 2025). National Plant Data Team, Greensboro, NC 27401-4901 USA.
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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. | | Click on the photo for a larger image
| | 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. | | Click on the photo for a larger image
| | 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. | | Click on the photo for a larger image
| | 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. | | Click on the photo for a larger image
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References used for identification and information:
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