Legumes

Many tree-sized species in the legume family are valuable for their hard, durable timber. North American species are relatively minor in this respect, although the Kentucky coffee tree, black locust, and honey locust are used as lumber to some degree.

Some leguminous species of tropical hardwoods are highly prized for fine woodworking. Purpleheart (Peltogyne paniculata) is a very hard, durable, and strong wood found in northern South America which is a brownish color when first sawn but turns a spectacular purple after being exposed to the atmosphere for a while. This tropical hardwood is used to manufacture fine furniture and as a decorative inlay into other woods. Rosewoods also have hard, dark-purple woods that are widely sought after to manufacture fine furniture and other goods. Examples include Brazilian rosewood (Dalbergia nigra) and Asian rosewoods (D. latifolia and D. sissoo).

Various species of trees in the genus Acacia are also important sources of lumber, for example, A. melanoxylan and A. visco in Australia. Species of Albizia are also important timber trees.

The seeds of the mesquite (Prosopis juliflora) of the southwestern United States and Mexico are used as animal feed, while the wood is burned to manufacture a flavor-enhancing charcoal. Mesquite flavorings have become quite popular in recent years, and many foods are now seasoned with this plant, including potato and corn chips.

Sunhemp is a fiber obtained from Crotalaria juncea, a legume native to south Asia. This is an annual plant, grown mostly in the Indian subcontinent and used to manufacture twine, ropes, bags, and canvas.

Gums are plant compounds that are used as adhesives, to manufacture paints and candies, to prepare paper, and to manufacture certain medicines. Important gums are made from extracts of certain legume species including gum tragacanth from Astragalus gummifer, gum Arabic from Acacia senegal and A. stenocarpa, and tragasol from the carob (Ceratonia siliqua).

The barks of some species of acacias are sometimes used as sources of tannins, chemicals that are mostly used to manufacture leather from animal skins. Species used for this purpose include Acacia dealbata, A. decurrens, and A pycnantha, all native to Australia but also cultivated elsewhere.

Some important dyes are extracted from species in the legume family. One of the world's most important, natural dyes is indigo, extracted from the foliage of the indigo (Indigofera tinctoria) of south Asia and to a lesser degree from American indigo (I. suffruticosa) of tropical South America. Indigos are still cultivated widely for their dark-blue dye, although similar chemicals have been synthesized and are now widely available.

Other important natural dyes are obtained from the heartwood of several species of leguminous trees. Logwood (Haematoxylon campechianum) is a small, thorny tree native to Central America that is an important source of a dye known as hematoxylin, which has a deep, purple-red color, and can also be manufactured into a persistent black dye. The brazilette (H. brasiletto) is a source of a natural red dye as are brazilwood (Caesalpina brasiliensis) and sappanwood (C. sappan) of south Asia.

Derris or rotenone is a poisonous alkaloid that has long been used by indigenous peoples of Southeast Asia as arrow and fish poisons. Rotenone is now used widely as a rodenticide to kill small mammals and as an insecticide to kill pest insects. This chemical is mostly extracted from the plants Derris elliptica and D. malaccensis.

Shellac is now a relatively minor product, but until recently it was widely used for finishing wood and for manufacturing products such as phonograph records and electrical insulators. Shellac is derived from a sticky substance that is secreted by an Asian insect, Tachardia lacca. However, several species in the legume family are cultivated as hosts for the insect, including the pigeon pea (Cajanus cajan) and babul tree (Acacia arabica).