Silver Bush Lupine

Silver Bush Lupine © KKorbholz

Silver Lupine
Lupinus albifrons var. albifrons
NATIVE

Description (Jepson, PlantID.net)

    • Eudicotyledon
      • Eudicots are a major lineage of flowering plants; see family for general characteristics
    • Pea / Legume 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 (flowers attached on short, equal stalks to a central stem)
      • Characteristic Pea / Legume 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
    Flowers © KKorbholz

    Distribution

      • 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 (Picking or removing any natural material from public land is illegal)

        • 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
        • Host plant for larval stage of 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
          Pod © KKorbholz
          • Bitter taste can deter herbivores
          • Some species are poisonous to livestock and humans

        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

          Notes

            • Like almost all members of its family, silver bush lupine fixes nitrogen; see Pea / Legume 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 6 lupine species, a remarkable number for a relatively small preserve and an indication of Edgewood’s species diversity
            • Lupinus albifrons has 5 varieties: Edgewood’s L. albifrons var. albifrons and 1 other variety are found in California and Oregon, while the other 3 varieties are only found in California
              • 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

            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 5 other lupine species at Edgewood
                • Miniature lupine (L. bicolor)
                • Fleshy lupine (L. affinis)
                • Chick lupine (L. microcarpus var. densiflorus)
                • Summer lupine (L. formosus var. formosus)
                • Arroyo lupine (L. succulentus)
              Silver Bush LupineMiniature LupineFleshy LupineChick LupineSummer LupineArroyo Lupine
              Growth Habitwoody shrubannualannualannualperennial herbannual; can appear a perennial herb
              Height≤ 16 ft., usually 3-5 ft.≤ 16 in.≤ 20 in.≤ 31 in.≤ 31 in.≤ 39 in.
              Hairinesssilver-hairyhairyhairysparsely to densely hairydensely hairyfleshy, sparsely hair
              Leaflet Tippointedsharply pointedrounded or pointed pointedsharply pointedwide, blunt
              Inflorescence Length≤ 12 in.≤ 3 in.≤ 8 in.≤ 12 in., often in distinct tiers≤ 12 in.≤ 6 in.
              Flower Colorblue-purple

              banner spot white to yellow > magenta
              blue

              banner spot white > magenta
              blue-purple

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

              no banner spot
              faded blue-purple

              banner spot white or none
              blue-purple

              banner spot white > magenta
              Fruit Arrangementcircle stemcircle stemcircle stemcluster to 1 sidecircle stemcircle stem
              Best Trailsall trailsRidgeview, Sunset, EdgewoodLower ClarkiaNative Garden, Upper SylvanUpper EdgewoodUpper Sylvan

              At Edgewood

                • Found in open chaparral and edge of grasslands
                  • Found in many areas of Edgewood, but especially prominent along the open areas of the Ridgeview trail
                  • See iNaturalist for observations of this plant
                    • Note observations are for 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.

                      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.

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

                          Thorp. R., Schroeder, P., and Ferguson, C. 2002. Bumble Bees: Boisterous Pollinators of Native California Flowers. Fremontia 30: 3-4.

                            Weiss, M. 1991, Nov. 21. Floral color changes as cues for pollinators. Nature, vol. 354, pp. 227-29.

                              Young, B. 1998, Jun. A Closer Look at Bush Lupine. Edgewood Explorer.