Gerald L. Klingaman
Plant Common Name
This entry has yet to be reviewed and approved by L2G editors.
The bean, legume, or pea family is a diverse, cosmopolitan group with many culturally and economically important members. It is the third largest plant family in existence with nearly 20,000 named species described. These flowering dicots may be trees, shrubs or herbs and exist everywhere worldwide save the icy poles. They are characterized by their elongated, many-seeded fruits (legumes) that open via longitudinal sutures. Most Fabaceae form root nodules containing symbiotic bacteria that fix atmospheric nitrogen. Some leguminous plants are armed with spines, which in a few cases harbor ants that defend the host plant against herbivores.
The Fabaceae are divided into three subfamilies: Mimosoideae (3000 species), Caesalpinioideae (2000 species), and Faboideae (more than 14,000 species). Most Mimosoideae are tropical trees and shrubs, and many are prized garden or greenhouse ornamentals. They typically have bipinnately compound leaves (divided into leaflets in feather-like fashion, with each leaflet likewise divided). Many members of this group exhibit diurnal leaf movement, with the leaflets folding at night. The small, tubular flowers are usually arranged in dense dome-shaped heads. Species in Albizia (silk-mimosas), Calliandra (powderpuff trees) and Mimosa have pincushion-like flower heads with long showy stamens. Acacia species (wattles or mimosa trees) typically have "fluffy" clusters of bright yellow flower heads.
Similar to Mimosoideae in size and composition, the subfamily Caesalpinioideae is home to many desirable ornamental trees and shrubs. Most are tropical, including Bauhinia (orchid trees), Cassia (shower trees), Delonix (flame trees or poinciana), and Parkinsonia (Jerusalem thorn). The Faboideae also contain a few highly prized cold-hardy ornamentals from genera such as Cercis (redbuds), Gleditsia (honey locusts), Gymnocladus (Kentucky coffee tree), and Senna (i.e., Senna hebecarpa and Senna marylandica, commonly known as wild senna). Members of the Caesalpinioideae usually have pinnately compound leaves. The flowers are asymmetrical, typically with three ascending and two down-facing petals. The blooms may be colorful and showy (as in Bauhinia and Cercis) or drab and inconspicuous (e.g., Gymnocladus dioicus).
By far the largest, most diverse, and most familiar subfamily of the Fabaceae, the Faboideae (or Papilionoideae) encompass herb, shrub, and tree species from across the globe. Members of this group are defined by their "papilionaceous" flowers, each bloom comprising a large upright petal (the "standard" or "banner"), two lateral petals (the "wings"), and a central "keel" of two united petals. The compound leaves are pinnate or trifoliate (with three leaflets), or rarely reduced to one leaflet. The Faboideae include numerous important herbaceous culinary species such as Pisum sativum (garden pea), Phaseolus vulgaris (garden bean) and Glycine max (soybean). Baptisia (false indigo), Lupinus (lupine), Lathryrus (sweet pea), Cytisus (broom), Robinia (locust), and Wisteria are among the many genera of ornamental herbaceous and woody plants that belong to the Faboideae.