Hemp has been cultivated in the United States since colonial times. The fibers of the central stem are quite strong; they have been used in making rope, paper, clothing, and other products. The foliage, flowers, and seeds of female plants contain chemicals with medicinal and recreational properties. However, since World War II, it has been illegal in Illinois and other areas of the United States to cultivate hemp. The industrial form of this plant is Cannabis sativa sativa (Hemp), while the medicinal and recreational form is Cannabis sativa indica (Marijuana). It is usually the industrial form of this plant that is encountered in the wild; it has a more robust habit of growth and contains lower levels of chemicals with medicinal and recreational properties. Hemp has a unique appearance and is easy to distinguish from other species of plants. A small specimen of Hemp superficially resembles some Potentilla spp. (Cinquefoils), especially Potentilla recta (Sulfur Cinquefoil), because of the similarity of their palmate leaves. However, the leaflets of Hemp are more elongated and tapered at their tips than Sulfur Cinquefoil. Furthermore, the flowers of Cinquefoils have 5 conspicuous petals that are white or yellow, like many other members of the Rose family, while the flowers of Hemp are devoid of petals.

This introduced plant is a summer annual about 3-9' tall. It is unbranched or little branched. The stout central stem is light green; where new growth occurs, this stem is more or less pubescent, but it becomes less hairy with age. The lower leaves are often opposite, while the upper leaves are alternate. These leaves are palmately compound with 3-9 leaflets (usually there are 5-7 leaflets). On large plants, these leaves can span up to 10" long and across (excluding the petioles), but they are half this size on smaller plants. While the lower leaves have long slender petioles, the upper leaves are nearly sessile. These petioles are more or less pubescent and occasionally reddish green. Each leaflet is narrowly ovate and coarsely serrated along the margins; the middle leaflets are larger in size than the lateral leaflets. The upper surface of each leaflet is dark green and sparsely pubescent. Hemp is dioecious with both male and female plants. The male plants produce both axillary and terminal panicles of male flowers. These panicles are up to 1' long; they have small leafy bracts and pubescent stalks. Each male flower is about 1/8" across, consisting of 5 sepals, 5 stamens with large anthers, and no petals. The oblong or lanceolate sepals are initially green, but they become cream or pale yellow with maturity. After these flowers have shed their pollen, the foliage of the male plant soon turns yellow and withers away. The female plants produce short axillary spikes of female flowers; these spikes are about 1" long and covered with glandular hairs. Each female flower is about 1/8" long, consisting of a single sepal, an ovary with two styles, and no petals. The sepal wraps around the ovary, forming a beak at its apex; the 2 styles are exerted from this beak. The surface of the sepal is green and covered with glandular hairs that exude a characteristic odor when they are rubbed. At the base of each female flower, there is a single green bract that is lanceolate and longer than the flower. There are small leaves and other bracts along the spike as well. The blooming period occurs from mid-summer to early fall and lasts about 1-2 months. Pollination is by agency of the wind. Upon maturity, the female flowers turn brown, but the foliage of female plants remains green until the fall. Each female flower is replaced by an achene containing a single large seed. The root system consists of a branched taproot. This plant often forms colonies at favorable sites.

Annual, 75 cm—1.5 (-2 5) in tall, slender; stem and branches slightly angular with appressed hairs (dense on younger shoots). Leaves palmately 3-9 (-11) foliolate, petiole ( .5) 2-10 (-12), cm pubescent, hairs white, appresed; lobes sessile, narrowly lanceolate, narrowed at base, palmtinerved, serrate, accuminate-caudate, 2-11 (14) cm long, 3-15 ( 20) mm broad; upper surface scabrid with stiff hairs topping the cystoliths; lower surface more or less densely pubescent, covered with sessile glands, stipules 4-6 mm long. Male flowers 4-6 mm across, greenish, pedicel 1-1.5 mm long, filiform. Tepals elliptic or oblong, finely pubescent, 3-4 ( 5) mm long, 1.5-2 mm broad, entire, acute. Stamen 4-5 mm long, Female flower as large as the perigonium; bracts foliaceous (-2) 4-13 mm long, covered with small glandular hairs, bracteole linear, 1.5-2.5 mm long. Perigonium entire, membranous, broadly ovate, beaked at the tip, compressed, much enlarged, contorted and rolled above the upper half in the fruit, up to 5-8 mm long, densely hispid or pilose, prominently ridged. Ovary sessile, sub-globose, C 0.5 mm long, styles 2-3 (-4) mm long, brown, caducous-pubescent. Achene 3-4 mm in diameter, shining, yellowish brown, minutely pilose to glabrous, ovate; seed only with fleshy unilateral endosperm.

Indian Hemp is widely cultivated in many countries for its valuable fibres for making ropes, strings etc. A strong narcotic is derived from the resin of stem, leaves, flowers and even the fruits, and the following products are obtained. (1) Ganja is derived from the resinous exudation from the female flowering top and unfertilized female flowers. (2) Charas is obtained by rubbing of the leaves, young twigs, flowers and young fruits (3) Bhang is derived from older leaves and mature fruits. Ganja and charas are smoked and Bhang is either used in the preparation of green intoxicating beverage known as “Hashish” or the manu¬facture of sweetmeet known as Majun. Bhang is much weaker than Charas and Ganja. The seeds are occasionally eaten and much valued for feeding birds. The seed oil is used as luminant and in making of paints, varnishes and soap.

A very adaptable species from plains to 10000 ft., grows abundantly on roadside especially in Northern regions.

Cannabis sativa is probably originally native to Central Asia, but its long cultivation makes it difficult to know its exact original distribution. This long cultivation and human selection for different desirable characteristics has resulted in considerable variation, but separation of it into either several species or the recognition of several varieties is probably not justified beyond the level of cultivated forms. Cannabis ruderalis Janischewsky, from Russia, is considered by some to be a distinct species from C. sativa.

The long, strong fibers are used in the paper-making industry and for weaving cloth, the seeds are a source of oil, the leaves, flowers, and fruit are used medicinally, and the female inflorescences (particularly the glandular leafy bracts and bracteoles) are used as a drug.

Plants 1-3 m tall. Branchlets densely white pubescent. Stipules linear. Leaves alternate; petiole 2-7 cm; leaf blade abaxially whitish green, strigose, and with scattered brownish resinous dots, adaxially dark green and with cystolith hairs; leaflets usually lanceolate to linear, (3-)7-15 × (0.2-)0.5-1.5(-2) cm with longest in middle, margin coarsely serrate, apex acuminate. Male inflorescences ca. 25 cm. Male flowers: yellowish green, nodding; pedicel 2-4 mm, thin; sepals ovate to lanceolate, 2.5-4 mm, membranous, with sparse prostrate hairs; petals absent; filament 0.5-1 mm; anthers oblong. Female inflorescences crowded in apical leaf axils among leaflike bracts and bracteoles. Female flowers: green, sessile; calyx sparsely pubescent; ovary globose, ± enclosed by appressed calyx, surrounded closely by bract and bracteoles. Persistent bracts yellow. Achene flattened ovoid, 2-5 mm; pericarp crustaceous, finely reticulate. Fl. May-Jun, fr. Jul.

Cannabis sativa has been reported as cultivated illegally and as apparently ruderal in all provinces and states except Alaska. It has been collected least frequently in Mississippi and Idaho. It seems to be best established in the prairies and plains of central North America.

Hemp is a short-day plant; flowering depends upon the latitude of origin. Races originating closer to the equator (and generally higher in psychointoxicant) require a longer induction period for flowering than races originating farther north.

The taxonomy of Cannabis sativa , a polymorphic species, has been debated in scientific and legal forums. The name C . sativa subsp. indica (Lamarck) E. Small & Cronquist has been applied to plants with a mean leaf content of the psychotomimetic (hallucinatory) delta-9-tetrahydrocannabinol of at least 0.3%; those with a lesser content fall under C . sativa subsp. sativa . When separate species are recognized, the name C . indica Lamarck has generally been applied to variants with high levels of the intoxicant chemical, whereas the name C . sativa Linnaeus, interpreted in a restricted sense, has generally been applied to plants selected for their yield of bast fibers in the stems. (The latter generally have taller, hollow stems with longer internodes and less branching than races selected for drug content.)

Superimposed on this dimension of variation is selection for nonabscising achenes in cultivation and abscising achenes in the wild (i.e., outside of cultivation). This is analagous to selection of nonshattering cereals from wild, shattering grasses. Achenes selected for cultivation tend to be longer than 3.8 mm and lack a basal constricted zone; by contrast, achenes selected for wild existence tend to be shorter than 3.8 mm and to have a basal constricted zone that seems to facilitate disarticulation and a mottled, persistent perianth apparently serving as camouflage.

Within Cannabis sativa subsp. sativa , the wild phase has been named C . sativa var. spontanea Vavilov (= C . ruderalis Janishevsky), in contrast to the domesticated C . sativa var. sativa . Within C . sativa subsp. indica , the wild phase (not to be expected in North America) has been designated C . sativa var. kafiristanica (Vavilov) E. Small & Cronquist, as distinct from the domesticated C . sativa var. indica . The chemical and morphologic distinctions by which Cannabis has been split into taxa are often not readily discernible, appear to be environmentally modifiable, and vary in a continuous fashion. For most purposes it will suffice to apply the name Cannabis sativa to all plants encountered in North America. *

The Iroquois used Cannabis sativa medicinally to convince patients that they had recovered. They also found it useful as a stimulant (D. E. Moerman 1986).

Staminate plants usually taller, less robust than pistillate plants. Stems 0.2-6 m. Leaves: petioles 2-7 cm. Leaflet blades mostly 3-9, linear to linear-lanceolate, 3-15 × 0.2-1.7 cm, margins coarsely serrate; surfaces abaxially whitish green with scattered, yellowish brown, resinous dots, strigose, adaxially darker green with large, stiff, bulbous-based conic hairs. Inflorescences numerous. Flowers unisexual, often transitional flowers and flowers of opposite sex developing later. Staminate flowers: pedicels 0.5-3 mm; sepals ovate to lanceolate, 2.5-4 mm, puberulent; stamens caducous after anthesis, somewhat shorter than sepals; filaments 0.5-1 mm. Pistillate flowers ± sessile, enclosed by glandular, beaked bracteole and subtended by bract; perianth appressed to and surrounding base of ovary. Achenes white or greenish, mottled with purple, ovoid, somewhat compressed, 2-5 mm, with ± persistent perianth that sometimes flakes off. 2 n = 20.