Pea Family

American Trefoil © AFengler

Legume Family
Fabaceae (fab-AY-see-ee)

Iconic Features

  • Leaves are compound, often pinnate
  • Leaves have stipules
  • Most plants with characteristic pea flower
  • Fruit is a legume (pea/bean pod)

Description (Jepson)

  • Eudicotyledons (eudicots) – a major lineage of flowering plants including most plants traditionally described as dicots and generally characterized by
    • 2 seed leaves (dicotyledon)
    • Netted (reticulate) leaf venation
    • Flower parts in fours and fives
    • Pollen grains with 3 pores (tricolpate)
    • Vascular bundles in stem arranged in a ring
    • Taproot system
  • Mostly herbaceous perennials
    • Also may be annuals, shrubs, or trees
  • Leaves
    • Compound (divided into leaflets) and entire (with smooth margins); often pinnate (arranged along a common axis, like a feather)
    • Generally alternate (1 leaf at each junction with stem)
    • All have stipules (a pair of leaf-like structures at the base of the leaf stalk), some modified to spines or glands
  • Flowers
    • The Pea family is divided into subfamilies, each with a unique floral design, though flowers are generally bisexual and bilaterally symmetrical
    • Pea subfamily (Faboideae / Papilionoideae), which includes most California species, have the characteristic pea flower, with 5 petals in a distinct arrangement
      • Banner – large upper petal with 2 lobes
      • Wings – 2 lateral petals
      • Keel – 2 lower, united petals, forming a narrow ridge, like the keel of a boat
    • Ovary superior (above the attachment of other flower parts)
    • Fruit is a legume (a single-chambered seed pod that opens along 2 seams)
Pea Flower © TElpel 


  • Approximately 19,400 species worldwide
    • Third largest plant family by number of species
    • Economically important family, including many commercially-grown species that provide significant sources of protein (e.g. peanuts, soybeans, beans, clovers)
    • Also includes highly weedy and invasive plants (e.g. broom, gorse, kudzu)
  • Almost all species have nitrogen-fixing nodules on their roots
    • Nodules host a bacteria (Rhizobium) that captures nitrogen gas (N2) from the air and converts it by a process called fixation into nitrogen compounds that plants can use
    • Host plant provides the bacteria with carbohydrates produced by photosynthesis and minerals
    • This symbiotic relationship allows Pea family members to grow in nitrogen-poor soil, like serpentine
    • When the plant dies, the fixed nitrogen is released, fertilizing the soil for other plants
    • Edgewood naturalist Paul Heiple notes that many Pea family species use nitrogen, in part, to form alkaloid-based toxins that discourage browsers from eating their protein-rich foliage and fruits (Heiple 2020)
  • CAUTION – some species, like locoweed (Astragalus), contain toxic alkaloids, especially in their seed coats, which can kill livestock
  • Greg Mendel’s experiments cross-breeding peas, conducted from 1856 to 1863, laid the foundations for the understanding of genetics
  • Scientific name from the defunct genus Faba, now in Vicia; faba is Latin for “bean”
  • Represented by 55 species at Edgewood

See General References

Specific References

Heiple, P. 2020, Jun. 14 & Jul. 2. Personal communications.

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.

Browse Some Edgewood Plants in this Family