Purple Owl’s-clover

Exserted Indian Paintbrush
Castilleja exserta ssp. exserta
NATIVE

Description (Jepson, PlantID.net)

• Eudicotyledon
  • Eudicots are a major lineage of flowering plants; see family for general characteristics
• Broomrape Family (Orobanchaceae)
• Annual herb, hemiparasitic
  • Densely hairy and glandular (sticky)
• Leaves
  • Alternate (1 leaf at each junction with stem), with blades attached directly to the stem (sessile)
  • Linear, can be threadlike, 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
    • Usually magenta with pink tips at Edgewood
  • Bilaterally-symmetrical flowers are usually white and magenta, 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 hooked, very hairy beak (a slender projection)
      • 3-lobed lower lip forms a pouch with 2 dark spots
    • Stigma (pollen-receiving part of the pistil/female structure) slightly exserted under the hook of 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)
  • Netted seed coat, characteristic of Castilleja species, is especially deeply-netted and loose-fitting
• Height to 18 in.

Distribution

• Native to California
  • Grows in grasslands
  • See Calflora for statewide observations of this plant
• Outside California, grows in Arizona and New Mexico
• Grows at elevations to 5,250 ft.

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

• Larval food source (host) for several butterfly species, e.g. Leanira checkerspot (Chlosyne leanira), variable checkerspot (Euphydryas chalcedona), and the endangered Bay checkerspot (Euphydryas editha bayensis)
  • Owl’s-clovers play a major role in efforts to re-establish the Bay Checkerspot Butterfly in 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
• exserta (ex-SER-ta) – from the Latin meaning “protruding out or extending beyond,” probably referring to the slightly exserted stigma
• 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 purple 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 dense-flowered owl’s-clover (C. densiflora)
• Formerly in the Figwort family (Scrophulariaceae)

ID Tips

• Often confused at Edgewood with dense-flowered owl’s-clover (C. densiflora ssp. densiflora)
  • 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)
• Purple owl’s-clover is the only one of these Castilleja species that has a hairy, hooked beak

	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 grasslands
  • See iNaturalist for observations of Castilleja exserta
• Flowers March – May

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.

Miller, L.B. 2004. 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.

Miller, L.B. 2004. 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.

Miller, L.B. 2004. 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.

Regents of the University of California. 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.

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.

Dave’s Garden.

Elpel, T.J. 2013. Botany in a Day: The Patterns Method of Plant Identification. HOPS Press, Pony, Montana.

Flora of North America. efloras.org.

Harris, J.G., and M.W. Harris. 2013. Plant Identification Terminology: An Illustrated Glossary. Spring Lake Publishing, Spring Lake, Utah.

Keator, G. 2009. California Plant Families. University of California Press, Berkeley and Los Angeles, California.

Native American Ethnobotany DB.

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