Western Larkspur

Western Larkspur © DSchiel

Foothill Larkspur
Delphinium hesperium ssp. hesperium

Description (Jepson, PlantID.net)

  • Eudicotyledon
    • Eudicots are a major lineage of flowering plants; see family for general characteristics
  • Buttercup Family (Ranunculaceae)
  • Perennial, upright herb
  • Leaves
    • Basal and cauline (along the stem)
    • Palmately lobed (3-14 lobes)
    • Margins deeply cut
    • Prominently veined
  • Flowers
    • Inflorescence (flower arrangement) is an elongated raceme (flowers attached on short, equal stalks to a central stem)
      • Generally less than 30 closely-spaced flowers
      • Pedicels (individual flower stalks) to 0.75 in. (Corelli 2004)
    • Each flower is bilaterally symmetrical
      • 5 blue-purple, petal-like sepals (usually green, outer flower parts)
      • 4 small central petals, paler blue-purple than sepals
      • Upper sepal forms a spur (tubular projection of a flower)
        • Encloses 2 smaller, nectar-containing spurs, formed by the 2 upper petals
    • Ovary superior (above the attachment of other flower parts)
  • Fruit is a follicle (a dry, multi-seeded pod that opens on one side)
  • Height to 20in.
Western Larkspur © GBarton


  • Native and endemic (limited) to California
    • Grows in grasslands and oak woodlands
    • 65 – 74% of plants occur on ultramafic soils, e.g. serpentine; see ultramafic affinity rankings (Calfora per Safford and Miller 2020)
    • See Calflora for statewide observations of this plant
  • Grows at elevations between 30 and 3,610 ft.

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

  • Wildlife
    • Pollinated by bumble bees, e.g. long-tongued California bumblebee (Bombus californicus) (Castillo 2009)
    • Larval food source (host) for some moth species, e.g. bilobed looper moth (Megalographa biloba) and spotted straw sun moth (Heliothis phloxiphaga)
  • Native people (for Delphinium species)
    • Young greens boiled for food
    • Blue dye made from the flowers
  • CAUTION – All parts of the plant are toxic, especially the seeds
    • California Poison Control System lists Delphinium species in the highest category of toxicity (level 4)
      • “Ingestion of these plants, especially in large amounts, is expected to cause serious effects to the heart, liver, kidneys or brain” (CPCS 2020)
    • Plants contain various poisonous alkaloids, including delphinine
    • Ingestion of some Delphinium species kill many cattle (and fewer numbers of horses and sheep), posing significant management problems for ranchers across western North America (Green, et al. 2020)

Name Derivation

  • Delphinium (del-FIN-ee-um) – from the Greek name for larkspurs, delphinion, derived from delphinos or delphis for “dolphin” due to the shape of the flower bud, and sometimes the flower, resembling that of a dolphin
  • hesperium (hes-PER-ee-um) – From the Greek for “of the west,” from hesperos, “of or at evening” or “the west,” as the sun sets in the west
  • Larkspur – a common name frequently used for species in the genera Delphinium and Consolida, also in the Buttercup family
    • Refers to the spur (horn-shaped nectary) of the flowers, which resembles the long, straight back claw of some larks
    • Delphinium species are also called lark’s heel (in Shakespeare), lark’s claw, and knight’s spur (Castillo 2009)
Spurs © FPeale


  • Larkspurs (Delphinium species) have an unusual arrangement of nested spurs, with two nectar spurs (tubular projections of flowers) inside another spur (Jabbour and Renner 2012)
  • Nectar spurs are examples of specialized relationships between flowers and pollinators that have coevolved
    • Spurs vary in length, shape, orientation, and color
    • This variation is associated with specialized adaptations in pollinators
      • The length of a floral spur, for example, limits pollinators to those adapted to reach the nectar
        • Generally, short-spurred flowers are pollinated by bees, medium-length spurred flowers by hummingbirds, and long-spurred flowers by hawkmoths (Blackmore 2018)
        • In the 1860’s, Charles Darwin and Alfred Russel Wallace famously predicted that a Madagascar orchid, Angraecum sesquipedale (Darwin’s orchid), with a foot-long spur, must have a pollinator with an equally long proboscis; 40 years later, a sphinx moth with a foot-long proboscis, Xanthopan morganii praedicta (Wallace’s sphinx moth), was discovered (Kindy 2021)
    • Nectar spurs have evolved independently in many different groups of flowering plants (angiosperms), an example of convergent evolution
      • Other species with pronounced floral nectar spurs at Edgewood include crimson columbine (Aquilegia formosa), in the Ranunculaceae family, and 3 rein orchids in the Orchid family (Orchidaceae)–chaparral rein orchid (Piperia elongata), elegant rein orchid (P. elegans ssp.elegans), and mountain rein orchid (P. transversa)
    • When spurs first develop in a plant lineage, a rapid flourishing of spur designs follows, creating many new species
      • Nectar spurs are considered examples of a key innovation, an adaptive breakthrough that drives a rapid diversification of species (Hodges 1996)
      • A strong correlation exists in many different plant lineages between the development of nectar spurs and subsequent proliferation of species
      • Columbines (Aquilegia species), for example, have been intensely studied to investigate the link between their relatively rapid speciation and the diversity of their floral spurs
  • Edgewood’s western larkspur 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

ID Tips

Royal LarkspurWestern LarkspurSpreading LarkspurCalifornia Larkspur
Habitatgrasslandsserpentine grasslandswoodlandswoodlands
Height≤ 20 in.≤ 20 in.≤ 24 in.≤ 63 in.
Inflorescencebranched raceme¹elongated raceme¹elongated raceme¹branched, elongated raceme¹
Flower Colorsepals royal blue

petals white and royal blue
sepals blue-purple

petals pale blue-purple

sepals and petals dark purple

sepals and petals pale lavender to greenish white
Pedicel² Length≤ 2 in.≤ 0.75 in.≤ 3 in.≤ 2.5 in.
Blooming PeriodFebruary-MayApril-JulyMarch-MayApril-July
¹raceme: flowers attached on short, equal stalks to a central stem
²pedicel: stalk of a single flower in a cluster
Royal Larkspur (L), Western Larkspur (LM), Spreading Larkspur (RM), California Larkspur
© DSchiel (L), GBarton (LM, RM, R)

At Edgewood

See General References

Specific References

Alexander, E.B. 2010, Oct. and 2011, Jan. Serpentine soils and why they limit plant survival and growth. Fremontia 38/39: 28-31.

Anderson, M.K. 2005. Tending the Wild. University of California, Berkeley. Pg. 268.

Blackmore, S. 2018. How Plants Work. Princeton Press, Princeton, New Jersey.

Bozhilova, M. 2019. Difference between Delphinium and larkspur. Difference Between.

California Poison Control System (CPCS). 2020. Plants. The Regents of the University of California.

Castillo, F. 2009, Jan. 24. The beautiful Delphinium. The Science of Flowers.

Frankie, G. et al. 2014. California Bees & Blooms: A Guide for Gardeners and Naturalists. Heyday, Berkeley, California.

Green, B.T. et al. 2020. Larkspur poisoning of cattle: Plant and animal factors that influence plant toxicity. Publications from USDA-ARS / UNL Faculty. 2294. United States Department of Agriculture, Agricultural Research Service, Lincoln, Nebraska.

Hodges, S.A. 1996. Floral nectar spurs and diversification. Abstract. International Journal of Plant Sciences 158(S6). Supplement: Morphology and Evolution of Flowers.

Jabbour, F. and S. Renner. 2012, Nov./Dec. Abstract. Spurs in a spur: Perianth evolution in the Delphinieae (Ranunculaceae). International Journal of Plant Sciences 173(9).

Kindy, D. 2021, Oct. 7. With a nearly foot-long proboscis, this new moth species holds the record for longest insect tongue. Smithsonian.

Mitchell, M. 2017. Ranunculaceae: Buttercup family — Delphinium (larkspur). Monterey County Wildflowers, Trees, and Ferns – Photographic Guide.

Safford, H.D. and J.E.D. Miller. 2020. An updated database of serpentine endemism in the California flora. Madroño 67(2): 85-104. BioOne Complete. PDF hosted by San Diego State University, San Diego, California.