Common Name: Hemp

General Information

Cannabis sativa is a variable, erect, usually branched, annual plant that can grow 2.5 metres tall, but is often smaller.
The plant is commonly cultivated for its fibre, edible seed and oil in many areas of the world, it is also a socially acceptable drug in areas of Asia and the Middle East[]. However, the plant is illegal to grow in Britain and many other western countries (plus Australia and New Zealand) because it contains certain narcotic principles and is a commonly used narcotic drug[, , ].

Known Hazards

The plant is a narcotic[, ]. Its action is almost entirely on the higher nerve centres, it can produce an exhilarating intoxication with hallucinations and is a widely used street drug[]. It has also been widely used in the past by mystics and sages wanting to communicate with the higher forces of nature. The nature of its effect does depend much on the temperament of the individual[]. The use of cannabis is considered to be less harmful than alcohol or tobacco by many people, nevertheless its use has been banned in many countries of the world including most western countries, New Zealand and Australia.

Botanical References

,

Range

W. Asia - Iran to India. A casual in Britain[].

Habitat

Fluvial deposits on crags and stony slopes[]. It is occasionally found as a casual on waste ground in Britain[]. It is especially found as a weed of nitrogen-rich soils near human habitations[]

Properties

Edibility Rating
Medicinal Rating
Other Uses Rating
Habit	Annual
Height	1.50 m
Pollinators	Wind
Self-fertile	No
Cultivation Status	Cultivated, Wild

Cultivation Details

Cannabis is reported to tolerate an annual precipitation range of 300 - 4,000mm, an average annual temperature range of 6 - 27°c and a pH in the range of 4.5 to 8.2[]. When grown for fibre, it requires a mild temperate climate with at least 670mm annual rainfall, with abundant rain whilst the seeds are germinating and until young plants become established[].
Cannabis is very adaptable to soil and climatic conditions[]. It prefers a rich loamy soil with plenty of humus[] but it succeeds in ordinary garden soil[] and also in calcareous soils[]. Cannabis thrives on rich, fertile, neutral to slightly alkaline, well-drained silt or clay loams with moisture retentive subsoils, it does not grow well on acid, sandy soils[]. Of the many types of hemp, some are adapted to most vegetated terrains and climates[].
Plants require little cultivation, except for weeding during early stages of growth. Hemp grows rapidly and soon crowds out weeds[]. After the plants are 20 cm tall, weeding is abandoned. Hemp tends to exhaust the soil of nutrients, though some nutrients are returned to the soil after plants are harvested[].
Cannabis sativa has a long history of cultivation dating back to at least 2,500 BCE. In that time many different varieties and cultivars have been developed for specific purposes such as fibre production (these forms are typically low in medicinally active compounds), oil-rich seeds, and medicinal/drug use. Selections grown for their mecicinally active compounds grow better and are more productive in tropical and subtropical regionss, whilst oil and fibre producing plants thrive better in the temperate and subtropical areas. Many of the cultivars and varieties have been named as to the locality where it is grown mainly. However, all so called varieties freely interbreed and produce various combinations of the characters. The form of the plant and the yield of fibre from it vary according to climate and particular variety.
Varieties cultivated particularly for their fibres have long stalks, branch very little, and yield only small quantities of seed and active compounds.
Varieties which are grown for the oil from their seed are short in height, mature early, produce large quantities of seed and varying quantities of active compounds.
Varieties grown for the active compounds are generally shorter, much-branched with smaller dark-green leaves.
Between these three main types of plants are numerous varieties which differ from the main one in height, extent of branching and other characteristics[].
At least one variety has been selected for its virtually insignificant content of the narcotic principles[]. This form is monoecious whereas most other forms are dioecious[]. There is also said to be a tall Chinese form that has no narcotic effect[]. However as of 1999 even these varieties are illegal to grow in most countries without a special licence. Certain varieties do not form many side-shoots and these are the forms most commonly grown for their fibre[].
Plants grown in warmer climates tend to be best for medicinal use, whilst those grown in more northerly latitudes produce the better fibre[].
The seed is very attractive to birds and is often included in bird seed mixtures[].

Edible Uses

Seed - raw or cooked. It can be parched and eaten as a condiment or made into cakes and fried[, , , ]. The seed is quite tasty, but it is very difficult to separate from the husk. We have tried grinding the seed, husk and all, and eating it this way, but it does then have a very gritty texture[]. The seed contains about 27.1% protein, 25.6% fat, 7.4% carbohydrate, 6.1% ash[]. A nutritional analysis is available calculated on a zero moisture basis[].

A highly nutritious edible oil, rich in essential fatty acids, is obtained from the seed[, ].

Leaves. Used in soups[]. The leaves contain 0.215% carotene[].

Medicinal

Hemp, or more appropriately cannabis since the form grown for fibre contains much less of the medicinally active compounds, has a very long history of medicinal use, though it is illegal to grow in many countries since the leaves and other parts of the plant are widely used as a narcotic drug[]. The leaves and the resin that exudes from them are the parts mainly used, though all parts of the plant contain the active ingredients[]. Cannabis contains a wide range of active ingredients, perhaps the most important of which is THC. The principal uses of the plant are as a pain-killer, sleep-inducer and reliever of the nausea caused by chemotherapy, whilst it also has a soothing influence in nervous disorders[]. Although cannabis does not effect a cure for many of the problems it is prescribed to treat, it is a very safe and effective medicine for helping to reduce the symptoms of many serious diseases. For example, it relieves the MS sufferer of the distressing desire to urinate, even when the bladder is empty. As long as it is used regularly, it also greatly reduces the pressure in the eye to relieve the symptoms of glaucoma.

The whole plant is anodyne, anthelmintic, antiemetic, anti-inflammatory, antiperiodic, antispasmodic, cholagogue, diuretic, emollient, hypnotic, hypotensive, laxative, narcotic, ophthalmic and sedative[, , , , , , , , , ]. It is used to relieve some of the unpleasant side effects suffered by people undergoing chemotherapy for cancer - in particular it is very effective in removing the feelings of nausea and indeed helps to create an appetite and positive attitude of mind which is so important to people undergoing this treatment[]. It has also been found of use in the treatment of glaucoma[, , ] and relieves the distressing constant desire to urinate that is suffered by many people with multiple sclerosis. Given to patients suffering from AIDS, it helps them to put on weight[]. Since it strongly increases the desire for food it has been found of benefit in treating anorexia nervosa. It is used externally as a poultice for corns, sores, varicose veins, gout and rheumatism[, ].

Few plants have a greater array of folk medicine uses. Cannabis has been used in the treatment of a wide range of conditions including alcohol withdrawal, anthrax, asthma, blood poisoning, bronchitis, burns, catarrh, childbirth, convulsions, coughs, cystitis, delirium, depression, diarrhoea, dysentery, dysmenorrhoea, epilepsy, fever, gonorrhoea, gout, inflammation, insomnia, jaundice, lockjaw, malaria, mania, menorrhagia, migraine, morphine withdrawal, neuralgia, palsy, rheumatism, scalds, snakebite, swellings, tetanus, toothache, uterine prolapse, and whooping cough[].

The seed is anodyne, anthelmintic, demulcent, diuretic, emollient, emmenagogue, febrifuge, laxative, narcotic and tonic[]. It is used to treat constipation caused by debility or fluid retention[]. The seed is an important source of essential fatty acids and can be very helpful in the treatment of many nervous diseases.

A high content of very active antibacterial and analgesic substances has been found in the plant[]. It has bactericidal effects on gram-positive micro-organisms, in some cases up to a dilution of 1:150,000[].

Agroforestry Uses:

A good companion plant for cabbages and other brassicas, it repels the cabbage white butterfly[, , , ] and also secretes a volatile essence from its roots that inhibits pathogenic micro-organisms in the soil[].

Other Uses

A drying oil is obtained from the seed. It is used for lighting, soap making, paints, varnish etc[, , , , , ]. In the temperate zone, oil is produced from females which have been left to stand after the fibre-producing males have been harvested[]. A varnish is made from the pressed seeds[]. Seed is harvested from the female plants when most of it falls off when the plant is shaken. Best time of day to harvest seed is in early morning when fruits are turgid and conditions damp. As fruits dry out by mid-day, seed loss increases due to shattering. Usually stems are cut and the seeds shaken out over canvas sheets or beaten with sticks to extract the seeds[].

A fibre is obtained from the stem. It is strong and very durable[] and is used in making coarse fabrics, rope etc[, , , , , ]. Male plants produce the best fibres and they are harvested when the plants turn brown and the flowers begin to open[, , ]. When used for making paper the stems are harvested in the autumn and either retted or steamed until the fibres can be removed. The fibre is cooked for 2 hours or more with lye and then beaten in a ball mill or Hollander beater. The paper is off-white in colour[].

Propagation

Seed - sow in early spring in the greenhouse. When they are large enough to handle, prick the seedlings out into individual pots and plant them out into their permanent positions in early summer. Seeds germinate well at low temperatures, but not below 1°C[].
The seed can also be sown outdoors in situ in mid spring.