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An agave plant, Agave fourcroydes, and the fiber obtained from its leaves. Henequen is produced only in Mexico, Cuba, and El Salvador. It is a hard plant fiber and is used to make rope, twine, and cord. Henequen is sometimes incorrectly called…

Any species of the genus Carya, formerly known botanically as Hicoria. Hickories are mostly tall forest trees characterized by strong, terminal, scaly winter buds; pinnately compound leaves (see illustration); solid piths (not chambered); and fruit…

Any species of the genus Ilex. The American species of holly (Ilex opaca) attains a maximum height of 40–50 ft (12–15 m) and has evergreen leaves. American holly grows naturally in the eastern and southeastern United States, close to the Atlantic…

A plant, Humulus lupulus, belonging to the family Cannabaceae. The hop plant is a rough-stemmed, tall-twining dioecious perennial herb and belongs to the same family as hemp and hackberries. It is propagated by cuttings of underground stems. The…

Any tree of the genus Ostrya of the birch family. Hophornbeam is represented in North America by two species, O. virginiana and O. knowltonii. Ostrya virginiana (American or eastern hophornbeam) is a small tree that may reach a height of 60 ft (18…

Any tree of the genus Carpinus of the birch family. Hornbeam is represented in the United States by C. caroliniana, the American hornbeam or blue beech. It is a small tree, sometimes attaining a height of 35 ft (10.7 m), and has a smooth,…

The science of breeding, raising, and caring for the horse. Successful horse production depends upon the use of the most recent advances in breeding methods (including artificial insemination and embryo transfer), feeding, physical conditioning,…

A hardy perennial crucifer, Armoracia rusticana, of eastern European origin belonging to the plant order Capparales (Brassicales). Horseradish (see illustration) is grown for its pungent roots, which are generally grated, mixed with vinegar and…

Intensively managed plants cultivated for food or for esthetic purposes. Plant agriculture is divided traditionally into the fields of agronomy (herbaceous field crops, mainly grains, forages, oilseeds, and fiber crops), forestry (forest trees and…

Alien species whose introduction does or is likely to cause environmental or economic harm to forests. Nonnative organisms that cause a major change to native ecosystems are generally referred to as invasive species or invasives; they also are…

Any of several low, perennial, tropical South American shrubs or half-shrubs in the family Rubiaceae. Ipecac plants (also termed ipecacuanha plants) are native to the tropical forests of Brazil and Colombia. Several species are used, but the dried…

The name given to any of at least 10 kinds of tree in the United States. Because of uncertainty as to just which tree is indicated, the name ironwood has been abandoned in the checklist of the native and naturalized trees of the United States.…

A shrub, Simmondsia chinensis, adapted to the arid portions of the southwestern United States and Mexico, and cultivated for a liquid wax that is extracted from its seed. Jojoba is a broadleaf evergreen shrub (see illustration) that is typically 1–3…

Any of the 53 tree and shrub species in the genus Juniperus occurring throughout the Northern Hemisphere. The common juniper (J. communis) is the most widespread of all conifers (ranging from subarctic tundra to semidesert and alpine mountains).…

A natural fiber obtained from two Asiatic species, Corchorus capsularis and C. olitorius (which are also termed jute), of the plant family Malvaceae (alternatively Tiliaceae). Jute plants (see illustration) are tall, slender, half-shrubby annuals…

Either of two cool-season biennial crucifers, Brassica oleracea var. acephala and B. fimbriata, of Mediterranean origin. Kale (see illustration) belongs to the plant order Capparales (Brassicales) and the plant family Brassicaceae (commonly known as…

A tropical tree, Ceiba pentandra, of the family Malvaceae (formerly Bombacaceae) that produces pods that contain seeds covered with a silky, cottony fiber. The kapok tree is a large tree, often reaching 45–60 m (150–200 ft) in height. It occurs in…

An annual, short-day, herbaceous plant, Hibiscus cannabinus (of the Malvaceae family), which is cultivated for its stem fibers. Kenaf (see illustration) usually grows upright, reaching 4.5 m (15 ft) in height, and is cylindrical and either branched…

A large, strikingly distinct tree, Gymnocladus dioica. The Kentucky coffee tree usually grows to a height of 80–90 ft (24–27 m), but sometimes attains a height of 110 ft (33 m) and a diameter of 5 ft (1.5 m). The species name, dioica, means that the…

A vigorous deciduous fruiting vine (family Actinidiaceae), and the name of the fruit itself, that is native to central China, where it commonly grows in moist and sheltered areas on the forest edges. Kiwifruit (Fig. 1), which belongs to the plant…

A cool-season biennial crucifer, Brassica oleracea var. gongylodes (alternatively B. oleracea var. caulorapa or B. caulorapa), of northern European origin belonging to the plant order Capparales (Brassicales). Kohlrabi (see illustration) is grown…

A perennial vine legume, of the genus Pueraria (order Fabales), capable of rapid growth in a warm temperate, humid subtropical climate. The name kudzu has a Japanese origin. Kudzu (Pueraria montana var. lobata; alternatively P. thunbergiana) was…

Fruit-bearing shrubs or small trees that are members of the genus Fortunella, included in the family of citrus fruits (family Rutaceae, order Sapindales). Kumquats are believed to have originated in China and the Malay Peninsula, but they are now…

A genus, Larix, of the pine family, with deciduous needles and short spurlike branches, which annually bear a crown of needles. The cones of the larch tree (see illustration) are small and persistent, varying by species in size, number, and form of…

Citrus limon, a small evergreen tree belonging to the order Sapindales that is cultivated for its fruit. The lemon is commercially the most important of the acid citrus fruits. It probably originated in the eastern Himalayan region of India, or…

A semi-viny annual legume, Lens culinaris (alternatively Lens esculenta), having pinnately compound, vetchlike leaves, and slender tufted and branched stems, cultivated for its thin, lens-shaped, edible seed. The lentil plant was one of the first…

A warm-season legume with trifoliate leaves, small purple pea-shaped blossoms, and one seed per pod. There are 15 American species and more than 100 Asiatic species that are categorized as lespedeza plants. Two annual species, Lespedeza striata…

A cool-season annual, Lactuca sativa, of Asian origin and belonging to the tribe Cichorium of the Compositae family. Lettuce (see illustration) is grown for its succulent leaves, which are eaten raw as a salad. Four varieties of this leading salad…

A product obtained from the licorice plant (Glycyrrhiza glabra) of the legume family [Leguminosae (Fabaceae)]. Licorice (alternatively spelled as liquorice) is a perennial herb that grows wild and is cultivated in southern Europe and in western and…

A tree of the genus Guaiacum having remarkable hardness. Lignumvitae (Latin for “wood of life”) is native in the Florida Keys, Bahamas, West Indies, Central America, and South America. In addition, it is cultivated to some extent in southern…

An acid citrus fruit, Citrus aurantifolia, usually grown in tropical or subtropical regions because of its low resistance to cold. There are two principal groups of limes: (1) the West Indian, Mexican, or key lime and (2) the Tahiti or Bearss lime.…

A name commonly applied to two trees: black locust (Robinia pseudoacacia) and honey locust (Gleditsia triacanthos). Both black locust and honey locust, which are commercially important trees, have podlike fruits similar to those of the pea or bean.…

Timber sawed or split into planks, boards, and similar products. Lumber can come in many forms, species, and types from a wide variety of commercial sources. Because most lumber is manufactured similarly and graded by standardized rules, it is…

A tree (Mangifera indica) grown throughout the tropical and subtropical areas of the world for the cultivation of its fruit. The mango (Mangifera indica) is a member of the cashew family Anacardiaceae (order Sapindales). Originating in Southeast…

The name (Spanish in origin) for the dried leaves, stems, seeds, and flowering tops of the hemp plant, Cannabis sativa, which can be smoked in cigarette form or in a pipe. Marijuana is the Spanish-derived name for the dried leaves, stems, seeds, and…

Fundamental principles governing the transmission of genetic traits, as discovered by Gregor Mendel. Mendelism is the term used to describe the basic laws of genetic inheritance (Fig. 1). These operating laws were formulated by Gregor Johann Mendel…

A common name applied to at least six related members of the grass family grown for their edible seeds: foxtail millet (Setaria italica), proso millet (Panicum miliaceum), pearl or cattail millet (Pennisetum glaucum; alternatively Pennisetum…

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…