Clay Mariposa Lily

Calochortus argillosus
NATIVE – CA ENDEMIC

Description (Jepson, PlantID.net)

• Monocotyledon
  • Monocots are a major lineage of flowering plants; see family for general characteristics
• Lily Family (Liliaceae)
• Upright, herbaceous perennial
  • Grows from a bulb (short underground stem with fleshy leaves, e.g. onion)
• Leaves
  • Narrow basal leaves, with alternating linear leaves along the stem
  • Wither before flowering
• Flowers
  • Inflorescence (flower arrangement) of 1-7 upright, white, cup-shaped flowers
  • 3 wedge-shaped white petals, with pink backs, and tawny streaks at base
  • Nectary glands with dense orange-red hairs
  • Narrow sepals (outer flower parts), tawny pink with darker streaks, curl back and often show between petal gaps
  • Ovary superior (above the attachment of other flower parts)
• Fruit is an erect capsule (a dry, multi-chambered fruit that splits open at maturity) with numerous seeds
• Height to 24 in.

Distribution

• Native and endemic (limited) to California
  • Grows in grasslands
  • See Calflora for statewide observations of this plant
• Grows at elevations to 2,600 ft.

Uses (San Mateo County Parks prohibits removal of any natural material)

• Wildlife
  • Pollen and nectar source for bees, beetles, and many other insects, including orange tortrix moth (Argyrotaenia franciscana) (Calscape 2018)
• Native people
  • Ate the bulbs boiled, steamed, roasted, or baked in earthen ovens (Anderson 2005)
  • In early spring, bulbs were peeled and eaten raw
  • Some tribes pounded dried bulbs into a flour and ate as a mush
  • See Lily family for more details about how Native people actively managed edible geophytes

Name Derivation

• Calochortus (kal-oh-KOR-tus) – from the Greek kallos, “beautiful,” and chortus, “grass,” referring to the leaves
• argillosus (ar-JILL-oh-sus) – from the Latin for “clay-loving,” referring to this species’ preference for clay soils
• Mariposa – Spanish for “butterfly,” for the intricate petal patterns reminiscent of butterfly wings

Notes

• Geophytes (e.g. plants growing from bulbs, corms, rhizomes, or enlarged taproots) are well adapted to survive fire, our Mediterranean climate’s long, dry summers, and extended droughts
  • Above-ground growth dies back after flowering, while underground the plant survives with stored water and nutrients
• The genus Calochortus is known for large, showy flowers above “beautiful grass” leaves
  • Range includes western North America, Mexico, and south to Guatemala
  • Greatest concentration of species is in California (Pacific 2025; Wood 2006)
    • The San Francisco Bay Area has 18 species – a center of Calochortus diversity! (Naumovich 2015)
  • Species are grouped into 3 flower forms
    • Globe lilies or “fairy lanterns” (nodding, globe-shaped flowers)
    • Mariposa lilies (open, upright flowers and wedge-shaped petals)
    • Cat’s ears and star tulips (open, upright flowers, pointed petals)
  • Edgewood has one globe lily (white globe lily) and two mariposa lilies (yellow mariposa lily and clay mariposa lily)
    • Cat’s ears can be found nearby in the Phleger Estate and Huddart County Park

ID Tips

• Differs from yellow mariposa lily (C. luteus)
  • Clay mariposa lily has white petals with red, pink, and yellow markings
  • Yellow mariposa lily has yellow petals with red-brown markings

At Edgewood

• Found primarily in serpentine grasslands
  • Favors areas with some seepage, as at the base of slopes
  • Grows in clay soils (hence the name), especially serpentine clay soils (Heiple 2025)
  • See iNaturalist for observations of this plant
• Flowers May-June

Specific References

Anderson, M.K. 2005. Tending the Wild. University of California, Berkeley.

Bock, G. 2024, May 28. Cal Hort Calochortus field trip (dudleyas, too). Succulents and More.

Gerritsen, M.E. and R. Parsons. 2007. Calochortus: Mariposa Lilies and Their Relatives. Timber Press, Portland, Oregon.

Heipel, P. 2025, August 27. Personal communication.

Naumovich, L. 2015, May 1. Calochortus lilies catch the eye. Bay Nature.

Pacific Bulb Society. 2025. Calochortus species one. Pacific Bulb Society Wiki.

Wood, M. 2006, Jun. 6. Yellow mariposa lily (Calochortus luteus). California Native Plant Society Yerba Buena Chapter.

General References

Calflora Database. 2014. Berkeley, California.

Calscape. 2018. California Native Plant Society.

Charters, M.L. 2015. California Plant Names: Latin and Greek Meanings and Derivations.

Charters, M.L. 2017. Southern California Wildflowers: Guide to the Pronunciation of Specific, Generic and Family Names.

Corelli, T. 2004. Flowering Plants of Edgewood Natural Preserve (2nd. ed.). Monocot Press, Half Moon Bay, California.

Flora of North America. efloras.org.

Native American Ethnobotany DB.

Regents of the University of California. Jepson eFlora. Jepson Herbarium. University of California, Berkeley.