Cottontop © DSchiel

Slender Cottonweed, Q-tips
Micropus californicus var. californicus

Description (Jepson,

  • Eudicotyledon
    • Eudicots are a major lineage of flowering plants; see family for general characteristics
  • Sunflower Family (Asteraceae)
  • Annual herb
    • Erect, with a central dominant stem
    • Entire plant gray-green, with short, soft, woolly hairs (tomentose) or cobwebbed
  • Leaves
    • Slender, slightly rounded, and tapering to base
  • Flowers
    • Inflorescence (flower arrangement) of 1-5 densely-clustered flowerheads
    • Each disciform flowerhead (see Sunflower family) with minute, white, unisexual flowers
      • 4-12 female (pistillate) peripheral flowers, obscured by densely-woolly chaff scales (paleae)
      • 2-5 functionally male (staminate) central disk flowers
    • Ovary inferior (below the attachment of other flower parts)
  • Fruit is an achene (a single-seeded, dry fruit that does not split open) without pappus (modified sepals, outer flower parts)
  • Height to 4 in. (Corelli 2004)


  • Native to California
    • Grows in thin soils in a variety of habitats, including grasslands, woodlands, disturbed areas, and chaparral
    • See Calflora for statewide observations of this plant
  • Outside California, grows from western Oregon to northwest Baja California, Mexico
  • Grows at elevations to 5,250 ft.

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

  • Wildlife
    • Secondary food source (host) for the larvae of the painted lady butterfly (Vanessa cardui) (Caldwell 2014)

Name Derivation

  • Micropus (my-KRO-pus) – from the Greek micros, “small,” and pous, “foot,” possibly referring to the tiny flowers
  • Cottontop – referring to the flowers, which resemble cotton-balls


  • Woolly hairs reflect harsh sun rays and help retain humidity
  • Edgewood’s cottontop is classified as a variety
    • Variety indicates a population with small morphological variations, e.g. color, seen throughout the geographic range of the species; interbreeding is possible
    • Subspecies indicates a geographically-separated population with distinct morphological characteristics; when not isolated, interbreeding is possible
    • In practice, botanists have not consistently applied these ranks
California Plantain (L), Cottontop (R)
© DSchiel

ID Tips

  • May be confused with the equally-small and unassuming California plantain (Plantago erecta) which often grows with cottontop in the same habitat
    • Cottontop’s flowers are hidden in its cobwebby hairs
    • California plantain’s flowers are visible

At Edgewood

  • Found in grasslands
    • See iNaturalist observations of Micropus californicus
  • Flowers April – June

See General References

Specific References

Breckling, B. 2008. Spring Wildflowers of Henry W. Coe State Park and the Inland San Francisco Bay Area. Pine Ridge Association.

Caldwell, J.A. 2014. California Plants as Resources for Lepidoptera: a Guide for Gardeners, Restorationists and Naturalists. Pg. 171.

Prigge, B.A. and A.C. Gibson. 2013. Micropus californicus var. californicus. A Naturalist’s Flora of the Santa Monica Mountains and Simi Hills, California. Web version, hosted at Wildflowers of the Santa Monica Mountains National Recreation Area. United States Department of Interior, National Park Service.