Dense-flowered Owl’s-clover

Denseflower Indian Paintbrush
Castilleja densiflora ssp. densiflora
NATIVE – CA ENDEMIC

Description (Jepson, PlantID.net)

• Eudicotyledon
  • Eudicots are a major lineage of flowering plants; see family for general characteristics
• Broomrape Family (Orobanchaceae)
• Annual herb, semi-parasitic
• Leaves
  • Alternate (1 leaf at each junction with stem), with blades attached directly to the stem (sessile)
  • Linear- or lance-shaped, usually with deeply-cut lobes
• Flowers
  • Inflorescence (flower arrangement) is a dense spike (single stem bearing stalkless flowers)
  • Bracts (modified leaves) at base of inflorescence and sepals (usually green, outer flower parts) are lobed and tipped white, pink, or purple
  • Bilaterally-symmetrical flowers are usually pink and white with purple and yellow accents
    • Tube-shaped, partially covered by bracts and sepals
    • 5 fused petals in two sets
      • 2-lobed upper lip creates a straight beak (a slender projection), usually a darker color than the lower lip
      • 3-lobed lower lip forms a pouch with 2 dark spots
    • Stigma (pollen-receiving part of the pistil/female structure) exserted above the beak
  • Ovary superior (above the attachment of other flower parts)
• Fruit is a capsule (a dry, multi-chambered fruit that splits open at maturity)
• Height to 16 in.

Distribution

• Native and endemic (limited) to California
  • Grows in grasslands
  • See Calflora for statewide observations of this plant
• Grows at elevations to 5,250 ft.

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

• Wildlife
  • Larval food source (host) for several butterfly species, e.g. Leanira checkerspot (Chlosyne leanira), variable checkerspot (Euphydryas chalcedona), and the endangered Bay checkerspot (E. editha bayensis)
    • Owl’s-clovers play a major role in efforts to re-establish the Bay Checkerspot Butterfly at Edgewood
• Native people
  • Harvested the seeds of owl’s-clovers (Castilleja species), which were an important food source (Anderson 2005)
  • Flowers were used in ceremonial wreaths

Name Derivation

• Castilleja (kas-til-AY-ha) – named for Domingo Castillejo Muñoz (1744-1793), a Spanish surgeon and professor of botany
• densiflora (den-si-FLOR-a) – from the Latin densa, “dense” and flores, “flowers,” meaning “densely flowered”
• Owl’s-clover – flower’s lower lip pouch with 2 spots looks like an owl’s face, and the inflorescence roughly resembles that of some clover species
  • The Spanish Californians called owl’s-clovers Escobitas, “little whisk brooms” (Bryant)

Notes

• Partial root parasite (hemiparasitic)
  • Capable of photosynthesis, but obtains nutrients and water from a variety of other plants (Heckard 1962)
  • Specialized root structures called haustoria (singular, haustorium) penetrate the host plant’s roots
• Colored bracts and sepals help attract pollinators
• Edgewood’s dense-flowered owl’s-clover is classified as a subspecies
  • Subspecies indicates a geographically-separated population with distinct morphological characteristics; when not isolated, interbreeding is possible
  • Variety indicates a population with small morphological variations, e.g. color, seen throughout the geographic range of the species; interbreeding is possible
  • In practice, botanists have not consistently applied these ranks
• Known to hybridize with purple owl’s-clover (C. exserta ssp. exserta)
• Formerly in the Figwort family (Scrophulariaceae)

ID Tips

• Often confused at Edgewood with purple owl’s-clover (C. exserta ssp. exserta)
  • See this 2019 Flickr post by Mark Egger for distinctions
• May also be confused with 2 other grassland Castilleja species at Edgewood: valley tassels (C. attenuata), and yellow cream sacs (C. rubicundula ssp. lithospermoides)

	Dense-flowered Owl’s-clover	Purple Owl’s-clover	Valley Tassels	Yellow Cream Sacs
Hairiness	slightly hairy	densely hairy (cobwebby)	slightly hairy	hairy
Inflorescence	dense spike	dense spike	narrow spike	bulging spike
Flower
Sepal Color	green to pink … light pink tips	magenta … pink tips	green … white or yellow tips	green
Petal Color	mostly white with pink … yellow and purple accents	white and magenta or pink … yellow and purple accents	white to pale yellow … yellow and purple accents	bright yellow to cream
Pouch¹	inflated	inflated	slightly inflated	greatly inflated
Beak²	straight … not hairy	hooked … densely hairy	straight … not hairy	straight … not hairy

At Edgewood

• Found in serpentine and non-serpentine grasslands
  • See iNaturalist for observations of Castilleja densiflora
• Flowers March – May

See General References

Specific References

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

Bryant, P.J. Castilleja exserta. Natural History of Orange County, California and Nearby Places.

Heckard, L.R. 1962. Root parasitism in Castilleja. Abstract. Botanical Gazette 124(1).

Mason, J. 2004. Scrophulariaceae — Figwort family characteristics [Illustration of owl’s clover beak, adapted]. T. Corelli. Flowering Plants of Edgewood Natural Preserve (2nd. ed.). Monocot Press, Half Moon Bay, California. (c) CC BY NC 3.0.

Miller, L.B. 2004. Castilleja attenuata [Illustration, adapted]. T. Corelli. Flowering Plants of Edgewood Natural Preserve (2nd. ed.). Monocot Press, Half Moon Bay, California. (c) CC BY NC 3.0.

—–. Castilleja densiflora ssp. densiflora [Illustration, adapted]. T. Corelli. Flowering Plants of Edgewood Natural Preserve (2nd. ed.). Monocot Press, Half Moon Bay, California. (c) CC BY NC 3.0.

—–. Castilleja exserta ssp. exserta [Illustration, adapted]. T. Corelli. Flowering Plants of Edgewood Natural Preserve (2nd. ed.). Monocot Press, Half Moon Bay, California. (c) CC BY NC 3.0.

—–. Castilleja rubicundula ssp. lithospermoides [Illustration, adapted]. T. Corelli. Flowering Plants of Edgewood Natural Preserve (2nd. ed.). Monocot Press, Half Moon Bay, California. (c) CC BY NC 3.0.

Mitchell, M. 2017. Orobanchaceae: Broomrape family — Castilleja (paintbrush & owl’s-clover). Monterey County Wildflowers, Trees, and Ferns – A Photographic Guide.

Press, M.C. 1998. Dracula or Robin Hood? A functional role for root hemiparasites in nutrient poor ecosystems. Oikos 82: 609-611. JSTOR.

Regents of the University of California. Castilleja exserta subsp. exserta [Illustration of beak, adapted]. Jepson eFlora. Jepson Herbarium. University of California, Berkeley.

—–. Castilleja rubicundula subsp. lithospermoides [Illustration of beak, adapted]. Jepson eFlora. Jepson Herbarium. University of California, Berkeley.

Shapiro, A.M. and T.D. Manolis. 2007. Field Guide to Butterflies of the San Francisco Bay and Sacramento Valley Regions. University of California Press, Berkeley and Los Angeles, California.