Cashew family (Anacardiaceae)

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Cashew family (Anacardiaceae)

The cashew family (Anacardiaceae) is a group of about 600 species of plants, most of which are tropical in distribution, although some occur in the temperate zone.

Almost all members of the cashew family are trees or shrubs, though some are vines. Many species have foliage, fruits, or bark on the stems and roots that contain an acrid, often milky resin, and saps that are irritating or poisonous if touched or eaten. The leaves are typically compound, with at least three if not more leaflets per leaf. The flowers are small, five-parted, insect pollinated, and arranged in compact inflorescences. The fruits are either a one-seeded drupe or a many-seeded berry, and are generally eaten and dispersed by birds or small mammals.

The fruits of some species in the cashew family are an important source of food for people, while other species are used in horticulture. Many species are considered to be important weeds because they are poisonous, often causing a severe dermatitis (rash) in exposed people.

Edible species of the cashew family

Various nuts and other fruits are obtained from species in the cashew family.

The cashew (Anacardium occidentale ) is the source of kidney-shaped cashew nuts. The cashew was originally from northeastern South America, but it is now planted widely throughout the humid tropics. The seedcoat of the fruit contains a toxic oil, and the raw cashew nut is also poisonous if eaten by people. However, the toxic chemical can be neutralized by roasting, and this richly delicious nut can be eaten safely.

The pistachio or green almond (Pistacia vera ) is native to Syria, but is now widely cultivated in the Mediterranean region, the southern United States, and elsewhere. These fruits are prepared for eating by roasting and are usually salted by a brief soaking in a brine solution. The natural color of the pistachio’s shell is white, but they are sometimes dyed red to make them more attractive to consumers.

The mango (Mangifera indica ) is an evergreen tropical tree that grows up to 98 feet (30 m) and is native to southern Asia. Its fruit is known as a mango, possessing a yellow-red skin with a large, flat seed surrounded by a tasty, juicy pulp, which can be yellow, red, or orange in color. However, there are numerous cultivated varieties of mangos varying greatly in the size, shape, and color of their fruits. The flavor of the mango is an exotic blend of sweet and acidic tartness, with an aromatic undercurrent. Mangos are an ancient, cultivated fruit, having been grown in tropical Asia for as many as 6,000 years, and achieving sacred status in some Indian cultures. Most mangos are eaten as a fresh fruit, but this food is also used to prepare sauces, jams, and chutney.

Other, less-well known tropical fruits in the cashew family include the ogplum, Jamaica plum, Otaheite apple (obtained from species of Spondias ) and the kaffir plum (Harpephyllum caffrum ) of southern Africa.

Other useful species

The lacquer tree (Rhus verniciflua ) occurs in China and Japan, where the viscous, milky sap of this plant has long been collected and applied as a natural varnish to fine wood carvings and furniture. The sap turns dark after oxidation in the atmosphere, providing an attractive, glossy coating to oriental lacquerware. A lacquer finish is resistant to heat, moisture, acid, alkali, and alcohol, and is therefore an excellent protection for fine works of art. Lacquering is an old art form, although it reached its greatest expression in China during the Ming Dynasty of 1368–1644 and in Japan during the seventeenth century. The finest pieces of lacquerware received hundreds of individual coatings, applied over a period of several years. Other minor sources of lacquer are the Burmese lacquer tree (Melanorrhoea usitata ) and an Indonesian sumac (Rhus succedanea ).

The leaves of some species in the cashew family are dried and processed as a source of tannins, chemicals that are useful for preparing leather. The Sicilian sumac (Rhus coriaria ) of southern Italy is especially useful, as its leaves can have a tannin concentration of 20–35%. This species is actually cultivated as a source of tannins, and it produces a superior soft leather with a pale color, considered especially useful for fine gloves and book covers. The red quebracho (Schinopsis lorentzii ) of South American temperate forests is another important source of tannins, which are obtained from the wood of this tree. The dried leaves of native sumacs (Rhus spp.) of North America have also been used as a minor source of tannins.

Chios mastic is a type of resin derived from the dried sap of Pistacia lentiscus of the Mediterranean region, while Bombay mastic is obtained from P. cabulica of southern Asia. These materials are used to manufacture a clear, high-grade varnish, which is sometimes used to coat metallic art and pictures, and in lithography.

The terebinth tree (Pistacia terebinthus ) was the original source of artists’ turpentine, but this solvent is now more commonly distilled from other types of trees. Another minor product is a yellow dye obtained from the twigs of the tropical South American tree Cotinus cuggygroa.

Ornamental species

Various species of sumac are grown as ornamentals. The staghorn sumac (Rhus typhina ) is cultivated for its attractive, purple-red foliage in the autumn and the interesting reddish horn-shaped fruiting inflorescences of female plants. This species is dioecious, meaning individual plants only bear female flowers (pistillate), or male flowers (staminate). The fragrant sumac (R. aromatica ) is also commonly grown in horticulture.

The South American pepper tree (Schinus molle ) is also grown as an ornamental shrub. So are the smoke trees, Cotinus obovatus of North America, and the introduced C. coggygria, with their diffuse and fuzzy smoke-like inflorescences, and attractive purplish foliage in autumn.

Key Terms

Inflorescence— A grouping or arrangement of florets or flowers into a composite structure.

Tannin— Chemicals that can be extracted from certain plants, and used to prepare leather from raw animal skins.

Weed— Any plant that is growing abundantly in a place where humans do not want it to be.

Wild species occurring in North America

Various species in the cashew family are native to North America. One of the more familiar groups includes species of vines and shrubs in the genus Toxicodendron, many of which contain a toxic oil that causes a contact dermatitis in people exposed to crushed foliage, stems, or roots. The most widespread species is known as poison ivy (T. radicans, sometimes known as Rhus radicans ), a plant with distinctive shiny compound leaves with three leaflets and shiny white berries. Poison ivy can grow as a perennial ground cover or as a vine that grows up trees. Other toxic species include poison oak (T. toxicodendron ) and poison or swamp sumac (T. vernix ), both of which are shrubs. The Florida poison tree or poisonwood (Metopium toxiferum ) grows in southern Florida.

Some people develop an increased sensitivity to this toxic oil with increased exposure; others appear to not have been initially affected by contact with poison ivy and its relatives, but subsequent exposures then elicit sensitive responses. In contrast, others appear to obtain a progressive immunity to the toxic oil of these plants. Especially severe poisoning can be caused if smoke from burning Toxicodendron biomass is inadvertently inhaled. Human deaths have been caused by this type of exposure, which can cause severe blistering of the pharynx and lungs.

Various species of sumac (Rhus spp.) occur as shrubs in North America. One of the more familiar species is the staghorn sumac (Rhus typhina ), the fruits of which are sometimes collected and used to prepare a lemonade-like drink. Other widespread species are the shining or mountain sumac (Rhus copallina ), smooth or scarlet sumac (R. glabra ), fragrant sumac (R. aroma-tica ), and ill-scented sumac or skunkbush (R. trilobata ).

The wild smoke-tree (Cotinus obovatus ) occurs in the southeastern United States and is sometimes grown as an ornamental shrub.

See also Poisons and toxins.

Resources

BOOKS

Conger, R.H.M., and G.D. Hill. Agricultural Plants. 2nd ed. Cambridge: Cambridge University Press, 1991.

Hartmann, H. T., et al. Plant Science. Growth, Development, and Utilization of Cultivated Plants. Englewood Cliffs, NJ: Prentice-Hall, 1988.

Judd, Walter S., Christopher Campbell, Elizabeth A. Kellogg, Michael J. Donoghue, and Peter Stevens. Plant Systematics: A Phylogenetic Approach. 2nd ed. with CD-ROM. Suderland, MD: Sinauer, 2002.

Kostermans, A.G.H., and J.M. Bompard. The Mangoes. Their Botany, Nomenclature, Horticulture, and Utilization. London: Academic Press, 1993.

OTHER

Palomar Community College—Wayne’s Word: An On-Line Textbook of Natural History. “Brazil, Paradise, and Cashew Nuts” <http://waynesword.palomar.edu/ecoph1.htm> (accessed November 10, 2006).