Practical
Plants

Cannabis sativa

Hemp

an annual member of the Cannabis genus in the family Cannabidaceae.

No photo available

Taxonomy and growth

Life cycle
annual
Height
2.5 m
Spread
0.8 m
Fertility
self sterile
Flower type
dioecious
Pollinators
Wind

Uses

Toxicity

Toxicity warning. The historical record reports a hazard for this plant. Do not use it to decide which parts are safe to eat or use medicinally.

The plant is a narcotic[15][34]. 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[28]. 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[28]. 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.

Edible uses

Seed - raw or cooked. It can be parched and eaten as a condiment or made into cakes and fried[17][35][9][13]. 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[K]. The seed contains about 27.1% protein, 25.6% fat, 7.4% carbohydrate, 6.1% ash[11]. A nutritional analysis is available calculated on a zero moisture basis[22]. A highly nutritious edible oil, rich in essential fatty acids, is obtained from the seed[2][13]. Leaves. Used in soups[27]. The leaves contain 0.215% carotene[11].

Plant part
Leaves
Product or use
Oil
Plant part
Seed

Medicinal uses

Historical medicinal uses. These records describe reported uses. They do not establish safety or effectiveness. Ask a qualified health professional before using any plant medicinally.

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[28]. The leaves and the resin that exudes from them are the parts mainly used, though all parts of the plant contain the active ingredients[28]. 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[28]. 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[28][32][21][29][5][8][10][16][24][26]. 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[K]. It has also been found of use in the treatment of glaucoma[19][23][24] 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[24]. 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[22][24]. 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, uteral prolapse, and whooping cough[27]. The seed is anodyne, anthelmintic, demulcent, diuretic, emollient, emmenagogue, febrifuge, laxative, narcotic and tonic[22]. It is used to treat constipation caused by debility or fluid retention[24]. 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[25]. It has bactericidal effects on gram-positive micro-organisms, in some cases up to a dilution of 1:150,000[25].

Product or use
Analgesic
Product or use
Anodyne
Product or use
Anthelmintic
Product or use
Antibacterial
Product or use
Antiperiodic
Product or use
Antispasmodic
Product or use
Cancer
Product or use
Cholagogue
Product or use
Demulcent
Product or use
Diuretic
Product or use
Emmenagogue
Product or use
Emollient
Product or use
Febrifuge
Product or use
Hypnotic
Product or use
Laxative
Product or use
Narcotic
Product or use
Ophthalmic
Product or use
Sedative
Product or use
Tonic

Material uses

A drying oil is obtained from the seed. It is used for lighting, soap making, paints, varnish etc[28][32][21][29][30][7]. In the temperate zone, oil is produced from females which have been left to stand after the fibre-producing males have been harvested[27]. A varnish is made from the pressed seeds[27]. 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[27]. A fibre is obtained from the stem. It is strong and very durable[7] and is used in making coarse fabrics, rope etc[1][32][21][29][30][31]. Male plants produce the best fibres and they are harvested when the plants turn brown and the flowers begin to open[3][7][27]. 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[14]. A good companion plant for cabbages and other brassicas, it repels the cabbage white butterfly[28][12][18][20] and also secretes a volatile essence from its roots that inhibits pathogenic micro-organisms in the soil[20].

Product or use
Fibre
Product or use
Paper
Product or use
Repellent

Environment

Range
W. Asia - Iran to India. A casual in Britain[6].
Habitat
Fluvial deposits on crags and stony slopes[33]. It is occasionally found as a casual on waste ground in Britain[6]. It is especially found as a weed of nitrogen-rich soils near human habitations[24]
Light
full sun
Shade tolerance
no shade
Water
moderate
Hardiness
Zone 9+
Soil textures
sandy, loamy, clay
Soil pH
very acid, acid, neutral, alkaline, very alkaline
Tolerates Nutritionally Poor Soil
No
Drought
intolerant

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[27]. The seed can also be sown outdoors in situ in mid spring.

Cultivation

Cannabis is very adaptable to soil and climatic conditions[27]. It prefers a rich loamy soil with plenty of humus[7] but it succeeds in ordinary garden soil[1] and also in calcareous soils[7]. When grown for fibre, it requires a mild temperate climate with at least 67cm annual rainfall, with abundant rain whilst the seeds are germinating and until young plants become established[27]. 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[27]. Of the many types of hemp, some are adapted to most vegetated terrains and climates[27]. Cannabis is reported to tolerate an annual precipitation range of 30 to 400cm, an average annual temperature range of 6 to 27°C and a pH in the range of 4.5 to 8.2[27]. Plants require little cultivation, except for weeding during early stages of growth. Hemp grows rapidly and soon crowds out weeds[27]. 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[27]. Hemp 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[24]. However, it 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[18][3][24]. As Cannabis sativa has been cultivated for over 4,500 years for different purposes, many varieties and cultivars have been selected for specific purposes, as fibre, oil or narcotics. Drug-producing selections grow better and produce more drug in the tropics; 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. Varieties which are grown for the oil from their seed are short in height, mature early and produce large quantities of seed. Varieties grown for the drugs are short, 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[27]. At least one variety has been selected for its virtually insignificant content of the narcotic principles[4]. This form is monoecious whereas most other forms are dioecious[4]. There is also said to be a tall Chinese form that has no narcotic effect[11]. However in 1999 even these varieties are illegal to grow in Britain without a special licence. Certain varieties do not form many side-shoots and these are the forms most commonly grown for their fibre[3]. Plants grown in warmer climates tend to be best for medicinal use, whilst those grown in more northerly latitudes produce the better fibre[28]. The seed is very attractive to birds and is often included in bird seed mixtures[32].

References

  1. F. Chittendon. RHS Dictionary of Plants plus Supplement. 1956 Oxford University Press 1951-00-00

    ↩1↩2

  2. Tanaka. T. Tanaka's Cyclopaedia of Edible Plants of the World. Keigaku Publishing 1976-00-00

    ↩

  3. ? Encyclopaedia Britannica. 15th edition.

    ↩1↩2↩3

  4. Carruthers. S. P. (Editor) Alternative Enterprises for Agriculture in the UK. Centre for Agricultural Strategy, Univ. of Reading 1986-00-00 ISBN 0704909820

    ↩1↩2

  5. ? A Barefoot Doctors Manual. Running Press ISBN 0-914294-92-X

    ↩

  6. Clapham, Tootin and Warburg. Flora of the British Isles. Cambridge University Press 1962-00-00

    ↩1↩2

  7. Hill. A. F. Economic Botany. The Maple Press 1952-00-00

    ↩1↩2↩3↩4↩5

  8. Yeung. Him-Che. Handbook of Chinese Herbs and Formulas. Institute of Chinese Medicine, Los Angeles 1985-00-00

    ↩

  9. Kunkel. G. Plants for Human Consumption. Koeltz Scientific Books 1984-00-00 ISBN 3874292169

    ↩

  10. Stuart. Rev. G. A. Chinese Materia Medica. Taipei. Southern Materials Centre

    ↩

  11. Reid. B. E. Famine Foods of the Chiu-Huang Pen-ts'ao. Taipei. Southern Materials Centre 1977-00-00

    ↩1↩2↩3

  12. Philbrick H. and Gregg R. B. Companion Plants. Watkins 1979-00-00

    ↩

  13. Facciola. S. Cornucopia - A Source Book of Edible Plants. Kampong Publications 1990-00-00 ISBN 0-9628087-0-9

    ↩1↩2

  14. Bell. L. A. Plant Fibres for Papermaking. Liliaceae Press 1988-00-00

    ↩

  15. Stary. F. Poisonous Plants. Hamlyn 1983-00-00 ISBN 0-600-35666-3

    ↩

  16. Emboden. W. Narcotic Plants Studio Vista 1979-00-00 ISBN 0-289-70864-8

    ↩

  17. Hedrick. U. P. Sturtevant's Edible Plants of the World. Dover Publications 1972-00-00 ISBN 0-486-20459-6

    ↩

  18. Riotte. L. Companion Planting for Successful Gardening. Garden Way, Vermont, USA. 1978-00-00 ISBN 0-88266-064-0

    ↩1↩2

  19. Huxley. A. The New RHS Dictionary of Gardening. 1992. MacMillan Press 1992-00-00 ISBN 0-333-47494-5

    ↩

  20. Allardice.P. A - Z of Companion Planting. Cassell Publishers Ltd. 1993-00-00 ISBN 0-304-34324-2

    ↩1↩2

  21. Lust. J. The Herb Book. Bantam books 1983-00-00 ISBN 0-553-23827-2

    ↩1↩2↩3

  22. Duke. J. A. and Ayensu. E. S. Medicinal Plants of China Reference Publications, Inc. 1985-00-00 ISBN 0-917256-20-4

    ↩1↩2↩3

  23. Foster. S. & Duke. J. A. A Field Guide to Medicinal Plants. Eastern and Central N. America. Houghton Mifflin Co. 1990-00-00 ISBN 0395467225

    ↩

  24. Bown. D. Encyclopaedia of Herbs and their Uses. Dorling Kindersley, London. 1995-00-00 ISBN 0-7513-020-31

    ↩1↩2↩3↩4↩5↩6↩7↩8

  25. Chopra. R. N., Nayar. S. L. and Chopra. I. C. Glossary of Indian Medicinal Plants (Including the Supplement). Council of Scientific and Industrial Research, New Delhi. 1986-00-00

    ↩1↩2

  26. Medicinal Plants of Nepal Dept. of Medicinal Plants. Nepal. 1993-00-00

    ↩

  27. Duke. J. Handbook of Energy Crops - 1983-00-00

    ↩1↩2↩3↩4↩5↩6↩7↩8↩9↩10↩11↩12↩13↩14↩15

  28. Grieve. A Modern Herbal. Penguin 1984-00-00 ISBN 0-14-046-440-9

    ↩1↩2↩3↩4↩5↩6↩7↩8↩9

  29. Uphof. J. C. Th. Dictionary of Economic Plants. Weinheim 1959-00-00

    ↩1↩2↩3

  30. Schery. R. W. Plants for Man.

    ↩1↩2

  31. Usher. G. A Dictionary of Plants Used by Man. Constable 1974-00-00 ISBN 0094579202

    ↩

  32. Chiej. R. Encyclopaedia of Medicinal Plants. MacDonald 1984-00-00 ISBN 0-356-10541-5

    ↩1↩2↩3↩4

  33. Komarov. V. L. Flora of the USSR. Israel Program for Scientific Translation 1968-00-00

    ↩

  34. Cooper. M. and Johnson. A. Poisonous Plants in Britain and their Effects on Animals and Man. HMSO 1984-00-00 ISBN 0112425291

    ↩

  35. Harrington. H. D. Edible Native Plants of the Rocky Mountains. University of New Mexico Press 1967-00-00 ISBN 0-8623-0343-9

    ↩

  36. J.M. Walker, S.M. Huang Cannabinoid analgesia Pharmacology & Therapeutics vol. 95 (2), p127?135 (2002/08/01)

  37. Robert Gable Comparison of acute lethal toxicity of commonly abused psychoactive substances Addiction vol. 99 (6), p686-696 (2004/02/12)

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