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The long, lustrous hair of the Angora goat, which originated in the area around Ankara (Angora), Turkey. The Angora goat (see illustration) probably originated before Biblical times because references to the use of goat's hair are found in the…

A genus, Morus, of trees characterized by milky sap and simple, often lobed, alternate leaves. White mulberry (M. alba) [see illustration] was introduced into the United States from China during the nineteenth century as a source of food for…

A hybrid sired by a male ass (Equus asinus) out of a female horse (E. caballus). The opposite cross, very seldom made, produces the hinny (a hybrid between a stallion and a female ass). The mule (see illustration) and the hinny are usually sterile,…

The edible fruit of Cucumis melo, belonging to the gourd family. Muskmelons (Fig. 1) are members of the family Cucurbitaceae (which includes other vine crops such as watermelons, squashes, pumpkins, and cucumbers) in the order Cucurbitales; they…

Any of a number of annual crucifer species of Asiatic origin belonging to the plant order Capparales. Mustards eaten as greens are Brassica juncea, B. juncea var. crispifolia, and B. hirta. Table mustard and mustard oils are obtained from B. nigra…

A smooth-skinned, fuzzless form of peach, Prunus persica var. nectarina. The nectarine (see illustration) probably was brought to the Middle East from Central Asia by Alexander the Great. The nectarine's lack of pubescence is a simple recessive…

A type of chemical used to kill plant-parasitic nematodes. Nematicides may be classed as soil fumigants or soil amendments, space fumigants, surface sprays, or dips. Soil treatments are commonly used because most plant-pathogenic species spend part…

Trees that can convert (fix) atmospheric nitrogen into a form that can be utilized for growth. The ability to convert (fix) atmospheric nitrogen into a form that can be used for plant growth is confined to bacteria and cyanobacteria. Plants fix…

Any of various evergreen trees of the genus Citrus, cultivated for its edible fruit. Orange trees (genus Citrus) belong to the family Rutaceae of the order Sapindales. The various trees classified as orange trees are most notable for producing…

Plants that are grown and used for decorative or display purposes. The use of ornamental plants (also termed ornamentals) [see illustration] developed early in history for it is known that primitive peoples planted them near their dwellings. There…

A soil of the past, that is, a fossil soil. Paleosols are most easily recognized when they are buried by sediments. They also include surface profiles that are thought to have formed under very different conditions from those now prevailing, such as…

A deadly fungal disease of bananas caused by a soilborne fungus. Panama disease, also known as Fusarium wilt of bananas (Musa species), is one of the most destructive fungal diseases of plants (Fig. 1). It is caused by a soilborne fungus, Fusarium…

A material useful for the mitigation, control, or elimination of plants or animals detrimental to human health or economy. Pesticides are formulated products that contain both active and inert ingredients. The active ingredients are the effective…

The use of plants to clean up environmental contamination of surface soils. Phytoremediation is more cost-effective and environmentally appealing than other currently available methods for soil detoxification. The most common approach for soil…

The application of genetic principles to the improvement of cultivated plants. The science of plant breeding involves the controlled mating and selection of plants, often utilizing hybridization and genetic engineering techniques, to modify plant…

A wood product in which thin sheets of wood are glued together, grains of adjacent sheets being at right angles to each other in the principal plane. Because of this cross-grained orientation, mechanical properties are less directional than those of…

Plants that produce biochemical compounds harmful to humans and other animals. While mechanical injury—for instance, from thorns—is probably the most common cause of human injury from plants, a great number of plants (Fig. 1) can cause injury…

The term commonly applied to the larger, orange-colored fruit of the Cucurbita species, used when ripe as a table vegetable, in pies, or for autumn decoration. Pumpkins, which grow on prickly vines with large lobed leaves and yellow flowers, belong…

Any of a number of South American trees belonging to different genera but having similar qualities, with all being a valuable source of wood, bark, and tannin. Quebracho trees, including those of the genus Schinopsis (family Anacardiaceae) [see…

The tree Cydonia oblonga of the order Rosales, originally from Asia, grown for its edible fruit. The deciduous, crooked-branched quince tree attains a height of approximately 20 ft (6 m). It is cultivated in either bush or tree form. The undersides…

Chenopodium quinoa, an indigenous pseudocereal of the Andean region of South America. Quinoa (Fig. 1) was one of the first plants to be domesticated in South America, and it is now recognized agronomically as an important crop. It has received…

A cool-season annual or biennial crucifer, Raphanus sativus, of Chinese origin, belonging to the plant order Capparales. The radish (see illustration) is grown for its thickened hypocotyl, which is eaten uncooked as a salad vegetable. Propagation is…

The plant Boehmeria nivea, a stingless member of the nettle family (Urticaceae), which is cultivated as a source of a tough, strong, durable, lustrous natural woody fiber. Ramie (see illustration), which is also known as China grass, is the only…

Brassica napus, a plant of the cabbage family. Rape (Brassica napus) [see illustration] and turnip rape (B. rapa or B. campestris), which are closely related, are members of the Brassicaceae (Cruciferae) plant family [order Brassicales or…

The horticultural name for certain species of the genus Rubus in the plant order Rosales. In these species, the raspberry fruit, when ripe, separates thimblelike from the receptacle (unlike the blackberry). Raspberry plants are upright shrubs with…

One of the bent grasses, Agrostis gigantea (also referred to as Agrostis alba) and its relatives, occurring in cooler, more humid regions of the United States on a wide variety of soils. Redtop grass (see illustration) tolerates both wet and dry…

A member of the pine family, Sequoia sempervirens, which is the tallest tree in the Americas. Redwood trees (see illustration) can attain a height of 350 ft (107 m) and a diameter of 27 ft (8.2 m). The range of redwoods is limited to a strip along…

The reestablishment of forest cover either naturally or artificially. Given enough time, natural regeneration will usually occur in areas where temperatures and rainfall are adequate and when grazing and wildfires are not too frequent. For example,…

The volume of soil around living plant roots that is influenced by root activity, either directly or via the activities of the microbiota that are stimulated by rhizodeposits (materials released by roots). Root–soil–microbiota interactions…

An herbaceous perennial, Rheum rhabarbarum or Rheum rhaponticum, of Mediterranean origin, belonging to the plant order Polygonales in older botanical classifications or Caryophyllales in newer classifications. Rhubarb (Rheum rhabarbarum or Rheum…

An annual cereal grass plant (Oryza sativa) cultivated for its carbohydrate-rich grain. Rice is the major source of food for nearly one-half of the world's population. Asian rice (Oryza sativa, family Poaceae, order Poales), simply referred to as…

Rosmarinus officinalis, a member of the mint family, grown for its highly aromatic leaves and as an ornamental. Rosemary is an evergreen and perennial herb that can live as long as 20 years under favorable conditions. Although many varieties exist,…

Hevea brasiliensis, a member of the spurge family (Euphorbiaceae) and a native of the Amazon valley. It is the natural source of commercial rubber. The rubber tree (see illustration) can reach 60–100 ft (18–30 m) in height, with a circumference of…

Those procedures, employed in areas outside incorporated cities and not governed by city ordinances, that act on the human environment for the purpose of maintaining or improving public health. Their purpose is the furtherance of community…

The plant Brassica napobrassica (also Brassica napus var. napobrassica), a cool-season, hardy biennial crucifer of European origin, belonging to the order Capparales and probably resulting from the natural crossing of cabbage and turnip. The…

A winter-hardy and drought-resistant cereal plant, Secale cereale, belonging to the grass family [Poaceae (Gramineae)], that is cultivated for its grain. Rye (Fig. 1) resembles wheat, with which it intercrosses to a limited extent. Rye is propagated…

An annual, thistlelike, oilseed crop, Carthamus tinctorius, belonging to the family Asteraceae (Compositae) in the order Asterales. Safflower produces its seeds in heads, and these seeds are used to yield a cooking oil. Each seed is shaped like a…

The plant Crocus sativus, which is a member of the iris family (Iridaceae) in the order Asparagales, and the spice derived from it. Originally a native of Greece and Asia Minor, saffron is now cultivated in various parts of Europe, India, and China.…

A shrubby perennial plant in the genus Salvia of the mint family (Lamiaceae). There are several species of sage, including garden, or true, sage (S. officinalis) [see illustration], which is the type most commonly used in foods. Many varieties of…

The name applied to any species of the genus Santalum of the family Santalaceae. The true sandalwood (Indian sandalwood) is the hard, close-grained aromatic heartwood of a root-parasitic tree, S. album, of the Indo-Malayan region. This fragrant wood…

Any of various tropical American vines of the genus Smilax (family Smilacaceae), and the flavoring material obtained from the roots of these vines. The roots of at least four species of sarsaparilla are used to obtain the flavoring material: S.…

A medium-sized tree, Sassafras albidum, of the eastern United States, extending north as far as southern Maine. Sassafras is said to live 700–1000 years. It can be recognized by the bright-green color and aromatic odor of the twigs and leaves. The…

A herb of the mint family in the genus Satureja. There are more than 100 species, but only S. hortensis (summer savory) and S. montana (winter savory) are grown for flavoring purposes. A number of varieties of each species are available, although no…

An extremely large tree, Sequoiadendron giganteum. The sequoia or giant sequoia (Sequoiadendron giganteum; formerly, Sequoia gigantea) [see illustration] is the only extant species of the genus Sequoiadendron (subfamily Sequoioideae, family…

Members of the genus Ovis in the mammalian family Bovidae. Sheep are bovids (members of the family Bovidae) belonging to the order Artiodactyla (the even-toed, hoofed mammals). Sheep were possibly the first animals to be domesticated about 11,000…

The lustrous protein fiber produced by silkworms (larvae of the silkworm moth); also the thread or cloth made from such fiber. Silk is a highly prized commodity by the consumer, even though certain manufactured fabrics now have some qualities that…

The theory and practice of controlling the establishment, composition, and growth of stands of trees for any of the goods (including timber, pulp, energy, fruits, and fodder) and benefits (water, wildlife habitat, microclimate amelioration, and…

An agave plant, Agave sisalana, and the fiber obtained from its leaves. The sisal plant (see illustration) is cultivated in Brazil, Haiti, Mexico, and several African countries, including Tanzania, Kenya, South Africa, and Madagascar. The coarse,…

The science that applies laws and principles of physics, especially continuum and particulate mechanics and hydraulics of porous media, to solve problems encountered in civil engineering that are related to force-deformation behavior of soil and the…

A chemical or physical process that results in the death of soil organisms. This control method affects many organisms, even though the elimination of only specific weeds, fungi, bacteria, viruses, nematodes, or pests is desirable. Even if complete…