Silver Bush Lupine

Silver Bush Lupine © KKorbholz

Silver Lupine
Lupinus albifrons var. albifrons

Description (Jepson,

  • Eudicotyledon
    • Eudicots are a major lineage of flowering plants; see family for general characteristics
  • Pea Family (Fabaceae)
  • Semi-deciduous perennial shrub, with a distinct woody trunk
  • Entire plant hairy
  • Leaves
    • Palmately compound (separate leaflets radiating from a single point)
    • Alternate (1 leaf at each junction with stem)
    • Upper and lower surfaces hairy, giving a silvery appearance
  • Flowers
    • Inflorescence (flower arrangement) is a tall spike-like raceme (unbranched stem with stalked flowers opening from the bottom up)
    • Characteristic Pea family flower is bilaterally-symmetric with a banner, wings, and keel
    • Violet to lavender, with a white or yellow patch at base of banner petal
    • Fragrant (some people smell grape soda)
    • Ovary superior (above the attachment of other flower parts)
  • Fruit is a hairy legume (a single-chambered seed pod that opens along 2 seams)
  • Height 2-16 ft.
Pea Flower © TElpel 
Flowers © KKorbholz


  • Native to California
    • Grows in a variety of habitats, including chaparral and coastal sage scrub, and dry, open areas of foothill woodlands and conifer forests
    • See Calflora for statewide observations of this plant
  • Outside California, extends into southern Oregon
  • Grows at elevations to 4,900 ft.

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

  • Wildlife
    • Native bees seek the pollen
      • Bumblebees are the principal pollinators as they have just the right weight to open the flower to reach the pollen
    • Authorities differ on the production of nectar in lupines, perhaps because nectar production may differ by species; see Ayers (2016) for a summary of the controversy
    • Larval food source (host) for multiple species of blue, hairstreak, and sulphur butterflies
      • One of 3 perennial lupines required as a host plant for larvae of the federally-endangered Mission blue butterfly (Icaricia icarioides missionensis)
  • CAUTION – Lupines contain varying amounts of toxic alkaloids
    • Bitter taste can deter herbivores
    • Some species are poisonous to livestock and humans
Pod © KKorbholz

Name Derivation

  • Lupinus (loo-PIE-nus) – from the Latin for “wolf”; it was mistakenly believed that lupines depleted soil of nutrients
  • albifrons (AL-bi-frons) – from the Latin for “white-fronded,” referring to the silvered appearance caused by hairs on the leaves


  • Like almost all members of its family, silver bush lupine fixes nitrogen; see Pea family for more details
  • Narrow, hairy leaves are adapted to conserve water in hot, dry habitat
  • Banner spot of lupine flowers changes color as the flower ages (Stead and Reid 1990)
    • This change occurs more quickly after pollination
    • Even though the flower shows no sign of wilting, color change tells visiting insects to move on to another flower
    • These unwilted, pollinated flowers remain to help attract pollinators from a distance
    • Flowers from more than 70 plant families use color changes to direct pollinators (Weiss 1991)
  • Edgewood has 7 lupine species, a remarkable number for a relatively small preserve and an indication of Edgewood’s species diversity
  • Edgewood’s silver bush lupine 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

ID Tips

  • Flowers and leaves of lupines are characteristically similar
  • At Edgewood, the silver bush lupine is the only lupine that is a perennial woody shrub
  • May be confused with the 6 other lupine species at Edgewood
    • Miniature lupine (L. bicolor)
    • Sky lupine (L. nanus)
    • Fleshy lupine (L. affinis)
    • Chick lupine (L. microcarpus var. densiflorus)
    • Summer lupine (L. formosus var. formosus)
    • Arroyo lupine (L. succulentus)
Silver Bush LupineMiniature LupineSky Lupine Fleshy LupineChick LupineSummer LupineArroyo Lupine
Growth Habitwoody shrubannualannualannualannualperennial herbannual; can appear a perennial herb
Height≤ 16 ft., usually 3-5 ft.≤ 16 in.≤ 24 in.≤ 20 in.≤ 31 in.≤ 31 in.≤ 39 in.
Hairinesssilver-hairyhairyhairyhairysparsely to densely hairydensely hairyfleshy, sparsely hairy
Leaflet Tippointedsharply pointedpointedrounded or pointed pointedsharply pointedwide, blunt
Inflorescence Length≤ 12 in.≤ 3 in.≤ 16 in.≤ 8 in.≤ 12 in., often in distinct tiers≤ 12 in.≤ 6 in.
Flower Colorblue-purple

banner spot white to yellow > magenta

banner spot white > magenta

banner spot white > magenta

banner spot white > magenta
white to yellow; rose to purple

no banner spot
faded blue-purple

banner spot white or none

banner spot white > magenta
Fruit Arrangementencircle stemencircle stemencircle stemencircle stemcluster to 1 sideencircle stemencircle stem
Best Trailsall trailsRidgeview, Sunset, EdgewoodLower ClarkiaLower ClarkiaNative Garden, Upper SylvanUpper EdgewoodUpper Sylvan

At Edgewood

  • Found in coastal scrub and grassland edges
    • Found in many areas of Edgewood, but especially prominent along the open areas of the Ridgeview trail
    • See iNaturalist for observations of Lupinus albifrons
  • Flowers March – May

See General References

Specific References

Ayers, G. 2016, Oct. 1. The controversy over nectar production. Introduction to genus Lupinus. American Bee Journal.

California’s endangered insects: Mission blue butterfly. Essig Museum of Entomology. University of California, Berkeley.

Elpel, T.J. 2013. Pea family – Fabaceae [Illustration of pea subfamily, adapted]. Botany in a Day: The Patterns Method of Plant Identification. HOPS Press, Pony, Montana.

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.

Stead, A.D. and M.S. Reid. 1990. The effect of pollination and ethylene on the colour change of the banner spot of Lupinus albifrons (Bentham) flowers. Annals of Botany 66: 655-663.

Thorp. R., P. Schroeder, and C. Ferguson. 2002. Bumble bees: Boisterous pollinators of native California flowers. Fremontia 30(3-4): 26-31.

Weiss, M. 1991, Nov. 21. Floral color changes as cues for pollinators. Nature 354: 227-229.

Young, B. 1998, Jun. A closer look at bush lupine. Edgewood Explorer.