Family Description

The legume family is a large group of dicotyledonous herbs, trees, shrubs and sometimes vines of cosmopolitan distribution. It consists of approximately 600 genera and 12,000 species. Leaves are compound, usually pinnate, with alternate arrangement. In species from arid regions, the leaves are often reduced leaving a leaf-like petiole known as a phyllode. Stipules are present, sometimes modified into thorns. Flowers are mostly 5¬merous and borne singly, in drooping or erect racemes, panicles, spikes or heads. Flowers are regular and composed of numerous exerted stamens combined into a pin-cushion like head or are more commonly irregular and called papilionaceous. Colors are in all shades and produced at any season. The fruit is a pod known technically as a legume.

The most characteristic features of the family are:
  • pinnately-compound leaves
  • the flowers
  • the legume

Plants in this family are easy to grow and usually possess considerable heat tolerance. They are best grown in well drained soils in sunny locations. Propagation is primarily by seed, which usually require scarification for good germination. Seeds germinate best with temperatures above 65°F. Pests are rare. Members of this family fix atmospheric nitrogen by means of Rhizobium bacteria which colonize the root system and produce nodules of various sizes.

The Fabaceae family is divided into three subfamilies. In the Mimosoideae, Mimosa pudica (sensitive plant) is a good example of this subfamily which is woody and found mainly in tropical and subtropical regions. The Caesalpinioideae, also primarily woody but both tropical and temperate, has Cercis canadensis as an example. In the Lotoideae subfamily, which contains most of the herbaceous plants of the family, Pisum sativum is an example.

Important herbaceous genera belonging to this family include Astragalus, Baptisia, Cassia, Desmodium, Lespedeza, Lupinus, Phaseolus, Pisum, Sabinea, Trifolium, and many woody species.


Lupinus polyphyllus (left) with papilionaceous flowers, Acacia sp. with numerous exposed stamens in a compact head (center) and a typical legume (pod), right.

Representative Species

     
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  Dolchos lablab Hyacinth Bean
* Lathyrus odoratus Sweet Pea
  Lespedeza thubergii Bush Clover
  Lupinus hybrids Lupines