Common Pacific Pea :

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 90^o; 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.

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

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 Pea²	American Vetch	Spring Vetch
Leaves
New Leaves	rolled like a cigar	flat	closed like a book
Stipules (pair of leaf-like structures at base of leaf stalk)	large (≤ 0.7 in.) and wavy-edged	small (~0.1 in.), star-like, with 3 teeth on lower half	small and toothed, with a dark-red dot
Flowers
Cluster	up to 15 flowers on a long raceme³	3-5 flowers on a long raceme³	1-2 flowers at junction with stem
Color	pastels; pale lavender to purple, fading to yellow-brown	dark purple banner; wings and keel pale purple to white	dark pink-purple
Banner Angle	bent 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 side	hairs all around	hairs 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)
³Raceme – 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

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.

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.

Mason, J. 2004. 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.

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.

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.

General References

Calflora Database. 2014. Berkeley, California.

Calscape. 2018. California Native Plant Society.

Charters, M.L. 2015. California Plant Names: Latin and Greek Meanings and Derivations.

Charters, M.L. 2017. Southern California Wildflowers: Guide to the Pronunciation of Specific, Generic and Family Names.

Corelli, T. 2004. Flowering Plants of Edgewood Natural Preserve (2nd. ed.). Monocot Press, Half Moon Bay, California.

Dave’s Garden.

Elpel, T.J. 2013. Botany in a Day: The Patterns Method of Plant Identification. HOPS Press, Pony, Montana.

Flora of North America. efloras.org.

Harris, J.G., and M.W. Harris. 2013. Plant Identification Terminology: An Illustrated Glossary. Spring Lake Publishing, Spring Lake, Utah.

Keator, G. 2009. California Plant Families. University of California Press, Berkeley and Los Angeles, California.

Native American Ethnobotany DB.

Regents of the University of California. Jepson eFlora. Jepson Herbarium. University of California, Berkeley.