Purple Owl’s-clover

Purple Owl’s-clover © DSchiel

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)
  • 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)

  • Host plant for the larvae of several butterfly species, including Leanira checkerspot (Chlosyne leanira), variable checkerspot (Euphydryas chalcedona), and the endangered Bay checkerspot (Euphydryas editha bayensis)
  • 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 rank is used to recognize geographic distinctiveness, whereas variety rank is appropriate for variants seen throughout the geographic range of the species; in practice, these two ranks are not distinct
  • Known to hybridize with dense-flowered owl’s-clover (C. densiflora)
  • Formerly in the Figwort family (Scrophulariaceae)

ID Tips

  • May be confused with 3 other grassland Castilleja species at Edgewood: dense-flowered owl’s-clover (C. densiflora ssp. densiflora), valley tassels (C. attenuata), and yellow cream sacs (C. rubicundula ssp. lithospermoides)
    • Purple owl’s-clover is the only one of these that has a hairy, hooked beak
Dense-flowered Owl’s-cloverPurple Owl’s-cloverValley TasselsYellow Cream Sacs
Hairinessslightly hairydensely hairy (cobwebby)slightly hairyhairy
Inflorescencedense spikedense spikenarrow spikebulging spike
Flower
   Sepal Colorgreen to pink

light pink tips
magenta

pink tips
green

white or yellow tips

green
   Petal Colormostly 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
   Pouch¹inflatedinflatedslightly inflatedgreatly inflated
   Beak²straight

not hairy
hooked

densely hairy
straight

not hairy
straight

not hairy
¹ Pouch: 3 lower fused petals
² Beak: 2 upper fused petals
Dense-flowered Owl’s-clover (L), Purple Owl’s-clover (LM), Valley Tassels (RM), Yellow Cream Sacs (R)
© DSchiel (L, LM, R), TCorelli (RM)
Dense-flowered Owl’s-clover (L), Purple Owl’s-clover (LM), Valley Tassels (RM), Yellow Cream Sacs (R)
© See Specific References

At Edgewood

  • Found in grasslands
    • See iNaturalist for observations of Castilleja exserta
  • 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. Botanical Gazette 124:1.

Mason, J. 2004. Owl’s clover beak [Illustration, adapted]. In 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, Castilleja densiflora ssp. densiflora, Castilleja exserta ssp. exserta, and Castilleja rubicundula ssp. lithospermoides [Illustrations]. In 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, & Ferns – A Photographic Guide.

Press, M.C. 1998. Dracula or Robin Hood? A functional role for root hemiparasites in nutrient poor ecosystems. Oikos, 82:3, pp. 609-611.

Regents of the University of California. Castilleja exserta subsp. exserta. [illustration of beak, adapted] in Jepson Flora Project (eds.). Jepson eFlora.

—–. Castilleja rubicundula subsp. lithospermoides. [illustration of beak, adapted] in Jepson Flora Project (eds.). Jepson eFlora.

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