woodsorrels

genus Oxalis

Member of woodsorrel family (family Oxalidaceae)
dicots (class Magnoliopsida)
flowering plants (subphylum Angiospermae)

Except for extremely rare examples that I don't expect to encounter, there are no other wild species of this genus in the bay area.

purple or pale flowers

Key features:

bract location on peduncle
leaf arrangement
stem branched or none

redwood sorrel
Oxalis smalliana

stem ± 0
leaf: < 10, clustered at rhizome tips
petiole < 20 cm, hairy
leaflets < 4 cm, often ± purple abaxially, midribs pale
Inflorescence: peduncle < 15 cm; bracts 2, near tip
sepals < 1 cm, lanceolate
petals < 2.5 cm, white to deep pink
± undisturbed forests

pale pink-sorrel
Oxalis incarnata

stem: erect, branched, < 30 cm, glabrous; axils often with bulblets
leaf: cauline, in whorl-like clusters of < 10, lower opposite or not
petiole 2–7 cm
leaflets < 1.5 cm
inflorescence: peduncle < 7 cm; bracts 2, near middle
sepals < 6 mm, oblong, acute, tips with 2 orange tubercles
petals < 2 cm, white to pale pink
Edgewood, near Santa Cruz, near Oakland/Berkeley

photo

purple woodsorrel
Oxalis purpurea

stem ± 0
leaf: < 8, in basal rosette; petiole < 5 cm
leaflets < 4 cm, sparsely hairy or more densely hairy abaxially and on margins
inflorescence: peduncle 1–11 cm; bracts 2, at or below middle
sepals < 1 cm, ± lanceolate, hairy
petals < 2.5 cm, purple to red, pink, or white [yellow]
Nisene Marks, Montara Mtn.

yellow flowers

Key features:

petal length
adaxial leaf hairs (dense appressed, sparse spreading, or none)

bermuda buttercup
Oxalis pes-caprae

stem generally underground
leaves in loose, ± basal rosette; petiole < 12 cm
leaflets < 3.5 cm, often purple-spotted, abaxially hairy
inflorescence: umbel-like, < 20-flowered; peduncle < 30 cm
sepals < 7 mm, lanceolate to oblong, tips often with 2 orange tubercles
petals < 2.5 cm, yellow

photos × 2

creeping woodsorrel
Oxalis corniculata

stem rooting at nodes, < 50 cm, hairs appressed to spreading
leaf cauline; petiole < 7 cm
leaflets < 2 cm, ciliate, hairs generally 0 adaxially, sparse, appressed abaxially
inflorescence: cyme, ± umbel-like or not, 2–7-flowered; pedicel < 1 cm, hairs appressed
sepals < 4.5 mm, linear to narrowly ovate
petals generally < 8 mm, oblong to spoon-shaped, yellow, sometimes with red spots below middle

hairy woodsorrel
Oxalis pilosa

stem erect to decumbent, < 40 cm, rooting at nodes or not, hairs 0.7–1.2 mm, dense, generally spreading
leaves cauline
leaflets < 1.5 cm, appressed-hairy
inflorescence: 1–3-flowered; pedicel < 2 cm, hairs dense, generally spreading, occasionally appressed
sepals 3.5–6 mm, lanceolate, tips ciliate
petals generally 8–12 mm, yellow

dwarf woodsorrel
Oxalis laxa

stem erect, < 20 cm, hairy
leaf cauline; petiole < 5 cm
leaflets < 13 mm, hairs sparse, spreading
inflorescence raceme-like, 6–14-flowered
sepals < 4 mm mm
petals < 12 mm, yellow

Toxicity of fire fern, lady's sorrel, oxalis, sorrel, shamrock (Oxalis spp.):
2b – These plants contain oxalate crystals but they do not cause immediate problems. These plants have tiny crystals that lodge in the kidneys and can cause kidney damage as well as nausea, vomiting and diarrhea.

5 observed taxons / 2 unobserved taxons / 1 key

Chris’s observations: 75 (73 are research grade)

Locations:

Fremont Older OSP: 7
El Corte de Madera OSP: 6
Purisima Creek Redwoods OSP: 6
Edgewood Park & Natural Preserve: 4
Waterdog Lake & Open Space: 4
Alum Rock Park, San Jose: 3
Butano SP: 3
Mt. Madonna SP: 3
Russian Ridge OSP: 3
Sam McDonald CP: 3
Big Basin SP: 2
Dry Creek Pioneer RP: 2
Nisene Marks SP: 2
Pescadero Creek CP: 2
Pleasanton Ridge RP: 2
Sierra Azul OSP: 2
Wilder Ranch SP: 2
Almaden Quicksilver CP
Coyote Hills RP
Crystal Springs Regional Trail
DeLaveaga Park, Santa Cruz
Dimond Canyon Trail, Oakland
Fort Ord NM
Garrapata SP
Guadalupe River Trail
Huddart CP
Lake Chabot RP
Portola Redwoods SP
San Pedro Valley CP
Sanborn CP
Santa Clara Central Park
Santa Teresa CP
Stevens Creek CP
Sweeney Ridge National Recreation Area
Windy Hill OSP
Wunderlich CP

Months:

Jan.: 5
Feb.: 11
Mar.: 20
Apr.: 8
May: 12
Jun.: 6
Jul.: 7
Aug.: 5
Sep.: 1

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Taxon info: iNaturalist – Calflora – Jepson eFlora – FNA

Bay Area species: iNaturalist – Calflora