Common Pacific Pea

Common Pacific Pea © KKorbholz

Hillside Pea
Lathyrus vestitus var. vestitus
NATIVE

Description (Jepson, PlantID.net)

  • Eudicotyledon
    • Eudicots are a major lineage of flowering plants; see family for general characteristics
  • Pea Family (Fabaceae)
  • Climbing, herbaceous perennial, with tendrils
  • Stems are 3-sided (triangulate in cross-section), often sharply-edged or flanged
  • Leaves
    • Compound (divided into leaflets) and pinnate (arranged along a common axis, like a feather)
    • 8-12 grey-green leaflets end in one or more coiling tendrils, which anchor the plant
    • Prominent arrow-shaped stipules (a pair of leaf-like structures at the base of the leaf stalk), with wavy edges
  • Flowers
    • Inflorescence (flower arrangement) of up to 15 flowers in a raceme (unbranched stem with stalked flowers opening from the bottom up)
      • Flowers fade to yellow-brown and remain on the stem
    • Characteristic Pea family flower is bilaterally-symmetric with a banner, wings, and keel
      • Banner, bent upward at about 90o; is light violet, lavender, or whitish, with purple lines (nectar guides)
      • Wings are pale violet to white
      • Keel, partly hidden by the wings, is white
    • Ovary superior (above the attachment of other flower parts)
  • Fruit is a pea pod, a kind of legume (a single-chambered seed pod that opens along 2 seams)
  • Height to 28 in.
Pea Flower

Distribution

  • Native to California
    • Grows in coastal sage scrub, chaparral, and oak woodlands
    • 55-64% of plants occur on ultramafic soils, e.g. serpentine; see ultramafic affinity rankings (Calflora per Safford and Miller 2020)
    • See Calflora for statewide observations of this plant
  • Outside California, grows from Oregon south to the Mexican border
  • Grows at elevations to 4,900 ft.

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

  • Wildlife
    • Frequented by insects (primarily large native bees) and hummingbirds for nectar
    • Host plant for the larval stage of silvery blue (Glaucopsyche lygdamus) and northern cloudywing (Thorybes pylades) butterflies
  • Native people
    • Ate raw seeds and greens
    • Made a decoction of roots for use as a general medicinal remedy
  • CAUTION – The fruits of many members of this genus contain a potent neurotoxin, which if not properly treated, can cause paralysis (Nature Collective 2020); best to avoid eating any wild peas
Pea Pod © DSchiel

Name Derivation

  • Laythrus (LA-thi-rus) – from the Greek lathyros, “pea”
  • vestitus (ves-TIE-tus) – from the Latin for “covered” or “clothed,” referring to hairs

Notes

  • Like almost all members of its family, common Pacific pea fixes nitrogen; see Pea family for more details
  • Each flower part plays a role in pollination (Broich 1983)
    • Banner petals are large, attracting attention
      • Red lines, called nectar or floral guides, direct insects to pollen and/or nectar
        • Some floral guides are invisible to the human eye unless viewed with ultraviolet light
      • Banner becomes erect only after anthers have shed ripe pollen into the keel
        • Flower is protandrous (male flower parts mature before female parts)
    • Wing petals are the “landing platforms” for pollinators
    • Anthers (pollen-producing part of the stamen/male structure) and stigma (pollen-receiving part of the pistil/female structure) are hidden in the keel
    • To get access, pollinators (primarily large native bees) must be heavy enough to depress the wings and keel, pushing the stigma out from between the keel petals
    • The stigma makes contact with the insect’s thorax and abdomen
      • Ripe pollen grains that have fallen into the keel are brushed up and onto the insect by hairs on the lower side of the stigma’s stalk (style)
      • The stigma receives pollen grains carried by the insect from other flowers  
  • Genus includes the garden sweet pea (L. odoratus), native to southern Europe
  • Edgewood’s common Pacific pea 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

  • May be confused with the several vetch (Vicia) species at Edgewood, including native American vetch (Vicia americana ssp. americana) and non-native spring vetch (Vicia sativa ssp. sativa)
Common Pacific Pea2American VetchSpring Vetch
Leaves
    New Leavesrolled like a cigarflatclosed like a book
    Stipules
    (pair of leaf-like structures at     base of leaf stalk)
large (≤ 0.7 in.) and wavy-edgedsmall (~0.1 in.), star-like, with 3 teeth on lower halfsmall and toothed, with a dark-red dot
Flowers
    Clusterup to 15 flowers on a long raceme33-5 flowers on a long raceme31-2 flowers at junction with stem 
    Colorpastels; pale lavender to purple, fading to yellow-browndark purple banner; wings and keel pale purple to whitedark pink-purple
    Banner Anglebent up at 90°bent up at less than 90°bent up at less than 90°
    Stigma1
    (pollen-receiving part of     pistil/female structure)
hairs on one sidehairs all aroundhairs all around
1 Peek, but don’t pick or tear apart to see the stigma
2 You can associate the pea, like its homophone, with bathroom items, i.e. toothbrush (stigma) and toilet paper (rolled leaves)
3 Raceme – an unbranched flower cluster with short, equal stalks
Common Pacific Pea (L), American Vetch (M), Spring Vetch (R), Stigma Hairs (illustration)
© DSchiel (L,R), KKorbholz (M), JMason (illustration)

At Edgewood

  • Found in woodlands
    • See iNaturalist for observations of Lathyrus vestitus
  • Flowers March – May

See General References

Specific References

Broich, S.L. 1983. A Systematic Study of Lathyrus Vestitus Nutt. ex T. & G. (Fabaceae) and Allied Species of the Pacific Coast. Doctoral Thesis. Oregon State University, Corvallis, Oregon.

Mason, J. 2004. Common Pacific pea  [Illustration of stigma, adapted]. T. Corelli. Flowering Plants of Edgewood Natural Preserve (2nd. ed.). Monocot Press, Half Moon Bay, California. (c) CC BY NC 3.0.

—–. American vetch [Illustration of stigma, 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. Fabaceae: Pea family — Vicia (vetch). Monterey County Wildflowers, Trees, and Ferns – A Photographic Guide.

Nature Collective. 2020. Chaparral sweet pea.

Prigge, B.A. and A.C. Gibson. 2013. Lathyrus vestitus var. vestitus. A Naturalist’s Flora of the Santa Monica Mountains and Simi Hills, California. Web version, hosted at Wildflowers of the Santa Monica Mountains National Recreation Area. United States Department of Interior, National Park Service.

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.