Eriogonum argillosum
Clay buckwheat
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Family: Polygonaceae · Type: Herb · Native
Conservation status: CNPS 4.3
Eriogonum argillosum (Clay buckwheat) is a native California herb in the Polygonaceae family, recognized by clay habitat, smooth fruit tips, and larger involucres (2.5-3mm) at branch tips.
Clay buckwheat is a California native annual found in southern San Francisco Bay and northern Santa Cruz Mountains on steep clay slopes, occasionally serpentine, at elevations of 150 to 600 meters. Flowering from March to October, this plant produces white to rose-colored flowers in delicate clusters on slender branchlets. Growing 10 to 30 centimeters tall with generally glabrous stems, it forms a compact annual herb with distinctive leaf characteristics. Its leaves are both basal and stem-based, featuring blades 1 to 3 centimeters long, with dense woolly undersides and a hairy upper surface. The tiny flowers measure 1.5 to 2 millimeters long, with oblong perianth lobes that create intricate terminal clusters.
Identification and appearance
Key characters: Co-occurs with 42 species; key features are clay habitat, smooth fruit tips, and larger involucres (2.5-3mm) at branch tips
Habitat and range
Habitat: Steep clay slopes, occasionally serpentine
Elevation: 150-600 m
California counties: San Benito, Monterey, Merced, Santa Clara, Fresno
Bloom period
Eriogonum argillosum blooms Mar-Oct.
Conservation status
CNPS 4.3
How to tell it apart
vs Adenostoma: Eriogonum has flowers in cup-like involucres; Adenostoma has tiny white rose-family flowers in spikes.; vs Salvia: Eriogonum has six similar perianth parts; Salvia has two-lipped tubular flowers.; vs Fagopyrum: Eriogonum has flowers in involucred clusters; Fagopyrum has loose branching sprays without involucres.; vs Artemisia: Eriogonum has cup-surrounded flower clusters; Artemisia has tiny inconspicuous heads in drooping sprays.; vs Chorizanthe: Eriogonum has multiple flowers per involucre; Chorizanthe has one flower per involucre with spiny teeth.
Frequently asked questions
Is Eriogonum argillosum native to California?
Yes. Eriogonum argillosum is native to California (recorded as native).
When does Eriogonum argillosum bloom?
Eriogonum argillosum blooms Mar-Oct.
Where in California does Eriogonum argillosum grow?
Eriogonum argillosum occurs in San Benito, Monterey, Merced, Santa Clara, Fresno, at elevations of 150-600 m.
What plant family does Eriogonum argillosum belong to?
Eriogonum argillosum is in the Polygonaceae family, genus Eriogonum.
Is Eriogonum argillosum rare or endangered?
Eriogonum argillosum carries California Rare Plant Rank 4.3, state rank S3S4.
Related species
Other California species in the same genus, family, or bioregion.
Sources: Jepson eFlora · CNPS Rare Plant Inventory · Index of California Plant Names · CalPhotos · CDFW CNDDB
Last updated 2026-10-07
Data from The California Species Project — 14,000+ California species with verified data from CNPS, CDFW, USFWS, Cal-IPC, and more.