Ornamental relatives of the pea in the family Fabaceae: Indigofera psuedotinctoria ‘Rose Carpet’; hybrid Baptisia ‘Chocolate Chip’; violet and pink Lupinus hybrids.

 

Legumes include some of the most nutritious plants on earth and some of the most toxic. In this family can be found vines, herbs, shrubs, annuals, perennials, and trees. The family now called Fabaceae is the third largest behind asters and orchids. Most plant families can be recognized by the organs in their flowers. The pea family might be more familiar for the appearance of its fruits. Like a pea pod, the fruits have seams on both sides of the pods, one usually acting as a hinge while the opposite seam splits open when ripe and dries to let the seeds fall out.

Perhaps the weirdest example of a legume pod is the peanut’s. Its flowering stem bends down to the earth and drives into the soil where the pod develops.

Soil is important in the development of legumes, not for what it gives the plants, but more perhaps for what the plants help to give back. The roots have a symbiotic relationship with rhizobia bacteria that can take nitrogen gas out of the air and make it available in a useful form to the plants themselves and others nearby in a process called nitrogen fixation. That soil-enriching benefit is one reason Fabaceae members like alfalfa are such popular cover crops grown to be turned under the soil and to enrich it.

Most of the pea family plants have compound leaves— pinnate or bipinnate like feathers or fern fronds. The finely divided leaves of many species appear to “pray” as they close up at night or on cloudy days. Mimosa pudica, called the sensitive plant, thrills children, closing instantly at the slightest touch or breath, and bowing when stroked. Mimosa has lent its scientific name as a common moniker to other species with similar feathery pinnate leaves and spherical powderpuff flowers.

In northern gardens, Albizia julibrissin (called mimosa) is a wide-spreading tree that can become a weed. In tropical climates, Acacia species (also called mimosa) are important trees everywhere they grow, as cut flowers, back-scratchers for elephants, the source of gum arabic, or harvested for expensive perfume.

Most Fabaceae flowers, however, are recognizable for resembling those of the sweet pea and grow either individually or together on upright stems like those of lupines, or in dangling racemes like wisteria vines. Redbud trees (Cercis canadensis) have tiny pea flowers that sprout right out of the woody branches of old growth.

Yellow false indigo, Baptisia ‘Carolina Moonlight’, with a background of the spring-flowering, gold-leaved shrub Spiraea thunbergii ‘Ogon’.