Pea Family

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)

Notes

• 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 hosts colonies of the bacteria Rhizobium
    • The bacteria capture nitrogen gas (N₂) from the air and convert it by a process called fixation into nitrogen compounds that plants can use
  • The 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)
  • Buckbrush (Ceanothus cuneatus var. cuneatus), like other Ceanothus species in the Buckthorn family, hosts colonies of a different nitrogen-fixing bacterium, Frankia ceanothi
• 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 54 species at Edgewood

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.

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.

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.

Browse Some Edgewood Plants in this Family