Present Day Cultivation of Cannabis
Cannabis is now widely distributed throughout the world, both in cultivated forms and as wild plants escaped over the years from cultivation sites. Large scale commercial production takes place in relatively few areas and a distinction can be drawn between its legitimate cultivation as a source of hemp fibre and seeds and the usually illicit
cultivation of cannabis as a source of narcotic materials. Whether a cannabis plant predominantly produces fibre (hemp) or narcotic resin is governed by both genetic and climatic factors (see Chapter 3). However, in general terms it can be said that the two properties seem inversely related and individual varieties can be classified as either drug type or fibre type (Bruneton, 1995) depending on the concentrations of the psychoactive compound THC and the non-narcotic cannabinoid, cannabidiol (CBD). The "drug" or "resin" type has a high THC concentration (>1%) and virtually no CBD. This property is observed amongst plants growing in warm climates and producing abundant narcotic resin. The "fibre" or "hemp" type, grown in northern temperate zones has very low THC levels (<0.3%, or even<0.03% for most cannabis varieties cultivated for fibre) and high CBD concentrations. However "intermediate" varieties are also found, with high levels of both THC and CBD. The general growth cycle of plants from the different varieties is similar, except for variations in maturation period (Clarke, 1981: p. 124) although the forms selected, harvesting methods and further processing depend on the purpose for which the plant is cultivated. The breeding and cultivation of cannabis plants with different characterisitics have been described in detail by Clarke (1981).
Cultivation of Cannabis for Hemp Fibre or Cannabis Seed
Despite its widespread cultivation in Europe and North America in the late 19th and early 20th centuries, the large scale production of hemp for fibre or seed is now restricted to a few areas of Eastern Europe (Hungary, Romania, Ukraine, Russia, former Czechoslovakia, Serbia, Croatia) and China (De Meijer, 1995). This is partly due to a great reduction in the demand for hemp fibre following the advent of more attractive alternatives (synthetic or natural), and secondly due to concerns and restrictions throughout the world on the cultivation of cannabis for narcotic purposes. Since 1961, the cultivation, trade and consumption of cannabis have been placed under restrictions worldwide following the United Nations Organisation's "Single Convention on Narcotic Drugs" (Brenneisen, 1983).
Whilst cultivation of drug type cannabis is universally prohibited or legally regulated, rules concerning cultivation of fibre (hemp) forms vary. In Canada, for example, the cultivation of any cannabis without special authorization has been prohibited since 1938, and all hemp fibre used in the country has to be imported (Anon., 1972). De Meijer (1995) has reviewed the availability and registration status of hemp cultivars in Europe. A number have been registered by the European Union (EU), which implies that their cultivation should be permitted by any member state. In practice, individual states may obstruct seed distribution and cultivation on a number of grounds including national drug legislation. In Italy, for instance, hemp cultivation is prohibited as long as a cultivar cannot be identified with a morphological marker linked to low THC-content (De Meijer, 1995). However, in France, a 1990 statute specifies 12 fibre varieties with not more than 0.3% THC which may be cultivated for the manufacture of speciality papers, non-woven products, furniture particle board, animal litter and so on. The producers must hold a contract specifying a buyer and use certified seeds from the authorised varieties (Bruneton, 1995). Cannabis is also legally cultivated for fibre and seed in Switzerland (Brenneisen, 1983).
There has been considerable recent interest in the development of hemp as an industrial crop in the Netherlands (De Meijer and Van Soest, 1992). Under the National Hemp Programme, the Centre for Plant Breeding and Reproduction Research (CPRO) have carried out a number of studies surveying variations in cannabis cultivars in terms of stem yield and quality, psychoactive potency, resistance to root-knot nematodes and plant morphology (De Meijer and Keizer, 1996), principally to evaluate their suitability as an arable source of paper pulp. A germplasm collection has been established at CPRO (De Meijer and Van Soest, 1992).
Fibre type cannabis is best grown in cold or temperate regions where the subsoil is moist and rain is abundant, since fibres produced in hot, dry climates are too brittle to be of commercial value (Bloomquist, 1971). The use of well-manured soil is recommended since this improves the quality of the fibres (Schultes, 1970). Commercially produced, high fibre varieties of even maturation time are selected to facilitate efficient harvesting. These are often monoecious strains which tend to mature more evenly than dioecious ones (Clarke, 1981: p. 15). Hemp bast fibre is produced in the phloem tissue of the stem. Consequently, the plants are grown close to each other so that branching is limited and long slender stems are produced (Fairbairn, 1976). The properties of hemp fibre, its harvesting and processing have been described by Judt (1995) and Clarke (1981: p. 150). Two types of fibres are present in cannabis stems—bark or bast fibres (23-28% by weight) and core fibres (75-70%). The two vary in their physical characteristics and chemical composition (Judt, 1995). Bark fibres are 20-22mm long and contain nearly 70% cellulose and small amounts of hemicellulose (10%) and lignin (5%). Compared to these, core fibres are considerably smaller in length (0.55mm) and have a lower proportion of cellulose (35%) and greater amounts of hemicellulose and lignin (20% of each).
Cannabis stalks are harvested at a point in the plant's growth (usually a prefloral stage) most appropriate to the best yield of fibre, before extensive lignification sets in (Clarke, 1981: p. 150). This is often a critical matter of a few days (Judt, 1995). A portion of the crop may be left to develop mature seed which can be used the following year. The harvested stalks are stripped of leaves, dried and stored in bales before further processing. Whole stalks may be pulped by chemical or mechanical means to obtain a heterogenous mix of fibres, whilst bast fibres may be separated by a process known as retting—partial rotting of the stems in water to destroy the other parts of the plant (Clarke, 1981: p. 150). Natural retting takes from a week to a month. The fibres are then dried, wrapped in bundles and stored in a cool, dry area.
Hemp fibre is relatively expensive to produce; in a study carried out in 1994 (Judt, 1995) to determine the viability of using hemp in the paper industry, the suggested prices of whole hemp stalks and the more valuable bast fibre were US $200 and US $630 respectively per air-dry ton as compared with US $78-199 for hard-wood pulp.
When the seeds are required as the commercial product, plants are cut only after seed maturation. Seeds fall easily from the floral clusters when mature and may be collected by hand or machine. The remainder of the plant may be used as pulp material (Clarke, 1981: p. 150).
Cultivation of Cannabis for Narcotic Use in India and Surrounding Areas
In Asia, cannabis grows wild throughout the Himalayas from Kashmir to Eastern Assam, up to altitudes of 10,000ft (Chopra et al., 1958). It extends down into parts of Pakistan, Bangladesh and India (Punjab, Bengal, Uttar Pradesh and Bihar) but in many of these areas, it is possible that wild growth of cannabis is supplemented by human factors arising from local use of the herb (Chopra et al., 1958; Evans, 1989). There are a few licensed growers of cannabis in Madhya Pradesh and Orissa (Anon., 1992), but illicit cultivation of cannabis is widespread not just in India, but throughout the tropical and sub-tropical areas of the world.
Due to its long historical association with the medicinal and narcotic use of cannabis, cultivation and harvesting practice in India is well documented (Chopra et al., 1958; Anon. 1992). Seed is sown in rows about 1.3m apart in rich, well-manured, weed-free soils; light or loamy soils are preferred (Evans, 1989; Chopra et al., 1958). Sowing takes place in June or July and harvesting in December or January. When the plants reach a height of about 20cm, they are thinned out and the lower branches removed to stimulate growth of the flowering branches. The narcotic components of cannabis (mainly THC) are found in a resin secreted by glandular trichomes on the leaves and flower bracts, particularly on pistillate flowers (Clarke, 1981).
In some areas, the tradition is that, as soon as flowering begins, the male plants are identified and systematically removed by the roots (Bloomquist, 1971). A common belief that the male plants are pharmacologically inactive is not true since similar amounts of cannabinoids may be produced in plants of either sex (Chiesa et al., 1973; Valle et al., 1968). However, male plants often yield less plant material, and the staminate bracts have fewer glandular trichomes than the pistillate ones (Clarke, 1981). It has further been shown that buds from unfertilized flowering tops of female plants are more potent (i.e. contain higher THC levels) than fertilised buds, and may even exceed some resin samples in cannabinoid content (El Sohly et al., 1984). When unpollinated, the pistillate plants start to produce more capitate glandular (resin producing) trichomes probably as a protection for the unfertilised ovule (Clarke, 1981). The product consisting of unfertilised flowering tops is referred to as "sinsemilla", derived from the Spanish words "sin" (without) and "semilla" (seed) (Rosenthal, 1984). It is highly valued not only for its greater potency, but also for its more intense aroma and enhanced appearance (Rosenthal, 1984).
To obtain sinsemilla, it is imperative that the male plants are removed meticulously before any large flower clusters appear, since even a single male flower is capable of yielding sufficient pollen to fertilise a large number of females. Male flowers growing in plant internodes can be used to to distinguish them from females at an early stage of their development (Rosenthal, 1984; Clarke, 1981). However, this practice requires much care and attention and the removal of male plants to produce sinsemilla buds is generally carried out only in small cultivation sites (El Sohly et al., 1984). Consequently seeds are commonly encountered in many of the commercial cannabis products (Baker et al., 1980b).
When grown for narcotic or medicinal use in India, the main parts of the cannabis plant harvested are the leaves, female flowering tops or the resin itself. Different harvesting and processing methods are used depending on the final product required
(Chopra et al., 1958; Anon., 1992). Bhang consists of larger leaves and twigs of the plant and is prepared by simply cutting the plants (wild or cultivated), drying them and beating them against a hard surface to separate the leaves. Both male and female plants may be used (Evans, 1989) and flowering parts are frequently present. Ganja or gunja consists of the dried flowering and fruiting tops of the female plant from which the resin has not been removed. Harvesting for ganja begins when the lower leaves begin to turn yellow. Spikes bearing the inflorescences are cut off and taken to the manufacturer's yard. For Bombay ganja, the plant material is piled into ridges and furrows and the material subjected to repeated treading by foot, turning over, drying and retreading. This results in the formation of compact sheaves which are made into piles and kept under pressure for a few days. The heaps are turned over, spread again and the treading repeated. The material is sifted to separate out dust, stones, seeds and leaves and then packed into a flat cake. For Bengal ganja, the withered flowering tops are not trampled on, but rolled by hand or foot to form rounded or sausage shaped masses.
According to Clarke (1981: p. 152), flowering tops or floral clusters are best dried by hanging the plants or clusters upside down, a method practised by some growers. This has the effect of allowing the leaves to hang next to the clusters and protect them from mechanical damage which may cause loss of the resin. The method also serves to enhance the appearance of the clusters when dry, since they appear larger than if they are compressed by laying flat to dry. During the drying process, the characteristics of the leaves and flowers change in that the unpleasant "green" taste of the cannabis is gradually lost in a process known as "curing". This does not happen if drying occurs too rapidly. However, too slow or incomplete drying may lead to deterioration of the plant material by the agency of micro-organisms (Clarke, 1981: p. 153). Removal of the outer leaves from the dried floral clusters known as "manicuring". Manicuring before drying may result in loss of resin potency due to greater breakdown of THC (Clarke, 1981: p. 153).
Another Indian product charas (or churrus) is the actual resin, in crude form, from the leaves and flowering tops. Men dressed in leather suits, jackets or aprons walk through the fields rubbing and crushing against the plants in the morning shortly after sunrise. The resin exuding from the leaf and flower trichomes sticks to the leather and can be scraped off (Samuelsson, 1992). Other methods include rubbing the flowering tops with the hands, from which resin is later scraped off, beating the flowering tops over a piece of cloth on which the resin collects as a greyish powder, or thrashing the tops against smooth concrete walls and collecting the powder and resin that stick to the wall (Samuelsson, 1992; Chopra et al., 1958).
Bhang, ganja and charas have been in use for many centuries in India. The dried and crushed flower heads and small leaves (ganja) from any geographical source, are commonly referred to as marijuana and the resin (charas) is referred to as hashish. Other names encountered for the different types of cannabis products described above are discussed further on in this chapter. Relatively recently, a further product of cannabis has entered the illicit market and is a concentrated liquid extract or oil produced by hot-solvent extraction or distillation of the resin (Brenneisen, 1983), or occasionally similar treatment of the herb or flowering tops (Baker et al., 1980b). Three to six kilograms of resin are needed to produce one kilogram of oil (Stamler et al., 1985), which may subsequently be dissolved in a vegetable oil (Anon., 1992).
The product contains high levels of THC and is commonly referred to as hash oil. This is not to be confused with cannabis seed oil which is a fixed oil devoid of narcotic properties.
Worldwide Cultivation Sites of Narcotic Cannabis
The international trafficking of cannabis products is mainly supplied from a few major source countries in tropical or sub-tropical areas of the world. Products originating in India or Pakistan are often seized by Customs officials, but other equally important producers are Colombia, Mexico, Jamaica, Morocco, Lebanon and Thailand (Bruneton, 1995; Stamler et al., 1985; Brenneisen and El Sohly, 1988). However, since this illicit trade is a lucrative one, smaller seizures of cannabis products originating from diverse parts of the world are encountered. These include other South American and Caribbean countries, Southern parts of North America, Egypt, Turkey and Nepal as well as various non-Mediterranean African countries viz. Ghana, Nigeria, Sierra Leone, Kenya, Zaire, Malawi, Zambia, Zimbabwe and South Africa (Baker et al., 1980a, b; 1982). Different strains of cannabis are grown in these locations, and consequently, the gross phenotype of the cannabis plants can vary from the short, broad strains of the Hindu Kush to tall meandering varieties found in Thailand (Clarke, 1981; pp. 102-118). Chemical characteristics of plants from different geographical origins are also known to vary (see Chapter 3).
Indoor Cultivation of Cannabis
As well as large scale cultivation in the aforementioned tropical or sub-tropical regions, a proportion of the cannabis used for hedonistic purposes is cultivated by individuals in temperate end-user countries either for personal use or supply. Indoor or greenhouse cultivation, which has been described extensively by Rosenthal (1984), reduces the problem of poor resin potency due to low outdoor temperatures and minimises the risk of detection by law-enforcement agencies (Stamler et al., 1985). Photoperiod can be controlled with the use of, for example, blackout screens in order to force flowering (Clarke, 1981, p. 148). Growth from seed can be successful, but in many of these illicit operations, vegetative propagation is carried out from stem cuttings of female plants, firstly in order to speed up propagation and secondly to ensure the sex of the plant. The cuttings may be grown either in soil or hydroponically, often without roots (Rosenthal, 1984). Hydroponic propagation of stem cuttings has the legal advantage, in the United States of America for instance, that the cutting is not classed as a "plant" if it lacks roots (Taylor et al., 1994). This assumes significance where the severity of sentencing is based on the total count of "plants" in the defendant's possession. As well as indoor cultivation of cannabis plants, clandestine small scale operations in Canada for producing hash oil have also been reported (Stamler et al., 1985).
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