Indian Hemp

Cannabis sativa L.

Synonyms - Cannabis indica, Cannabis ruderalis

Family: Cannabaceae

Names:

Cannabis is from the Greek name for hemp - kannabis.
Sativa is Latin for sown or planted referring to it as the cultivated form.
Indian Hemp refers to the smaller variety grown in India for its high drug content.
Marijuana is from the Mexican Spanish name of the plant - marihuana or mariguana

Other Names:

Bang
Dacha (South Africa)
Grass
Hashish
Hemp
Industrial Hemp
Makdagga (South Africa)
Marijuana
Pot
Redroot
Russian Hemp

Summary:

An erect annual sub shrub, usually 1-2 metres tall with 5-9 finger like leaflets arranged like fingers on a hand. The edges of the leaflets have forward pointing teeth. The stems are hollow, tough and angular. There are separate male and female plants. The females have leafy heads containing the small green flowers and seeds. It is often cultivated in secluded places for its illicit drug content.

Description:

Cotyledons:

Two. Oval. Tip round. Edges smooth, rounded. Base tapered. Short petiole. Hairless.

First leaves:

Opposite. Oval to spear shaped. Tip pointed. Edges lobed or toothed. Prominent parallel veins. Hairy.

Leaves:

Opposite near the base, alternate near the top.
Stipules -
Petiole - 40-50 mm long. Shorter than blade. Hairy.
Blade - Dark green on top paler underneath, palm like with 5-11 spear shaped leaflets with forward pointing teeth and prominent veins. Leaflets 50-100 mm long x 10-20 mm wide. Prominent veins running obliquely from the midrib to the tip of each tooth. Sparsely hairy on the upper surface with short, stiff, globose hairs usually with a short projecting point. More densely hairy underneath with longer, less swollen hairs similar to those on the stem, petiole and flowers.

Stems:

Erect, bushy, hollow, slightly grooved or angular, rough, slightly woody, 2000-7000 mm tall x 12-25 mm diameter. Single stem or sparsely branched. Inconspicuously hairy, with long or short hairs that have a slightly swollen base. Hairs on the upper stem exude a sticky resin with a characteristic odour. Aromatic.

Flower head:

Male and female plants (dioecious).
Male flowers on narrow, loose or open panicles arising from the upper leaf axils or at the ends of branches. Each flower has a small bract or leaf underneath.
Female flowers are in erect, leafy spikes arising from upper leaf axils. Each flower has a leaf underneath and a thin sepal with sticky hairs wrapped around the ovary. Flowers are in pairs on the female plant.

Flowers:

Male and female types. Small and green.
Ovary -
Sepals - One with sticky hairs wrapped around the ovary
Petals - Small.
Stamens -
Anthers -

Fruit:

Egg shaped, yellow green to brown, mottled when ripe.

Seeds:

Globular. 2.5-4 mm diameter. Yellow to olive brown or grey, may be mottled when ripe. May be slightly flattened. Tip rounded. Edges smooth. Surface has prominent veins. Base has stalk remnant.

Roots:

Many branched taproot to depths of 300-1000 mm with a mass of laterals in the top 200 mm.

Key Characters:

Dioecious.
Palmate leaves with like with 5-11 spear shaped leaflets with forward pointing teeth and prominent veins

Biology:

Life cycle:

Annual. Seeds germinate in spring to summer and the plants take about 110 days to mature. Flowering starts in January and may continue until late autumn. Male plants turn yellow and die after shedding much pollen. Female plants grow until all seed has ripened or it is damaged by frost.

Physiology:

Frost sensitive. Tolerates a wide range of temperatures and is drought tolerant once established. It is not very competitive in crops.

Reproduction:

By seed only.

Flowering times:

January until late autumn.

Seed Biology and Germination:

Vegetative Propagules:

None.

Hybrids:

Some botanist split the genus into three species - Cannabis sativa, Cannabis indica and Cannabis ruderalis.

Allelopathy:

Population Dynamics and Dispersal:

Spread by the abundantly produced seed which may be moved by water flows or birds. The main method of spread is by intentional plantings.

Origin and History:

Native to Central Asia.
It has been grown in China for at least 6000 years. The seed was extracted from the very toxic fruit and used as a food grain but has been superseded by millet, barley, rice and soybean. Oil extracted from the seed was used for frying and as a linseed oil alternative. Therapeutics and hallucinogens were obtained from the leaves, fruits and roots. The most active principle is THC (tetrahydrocannabinol) a cannabinol.
In Europe it has been cultivated for rope and clothing made from its fibre. It was important for sailing ships when 100 tonnes of hemp fibre was required to fully rig a ship. It was introduced to South America in the 1500's and North America in the 1600's and was an important crop until the civil war. It is still grown in the Soviet Union, Poland, Italy and Spain for cordage.
In NSW it was grown as an experimental crop in 1892 along the Hunter River and naturalised populations occur near Singleton and other areas. It has also naturalised in SA probably escaping from illicit plantings. It is has a high potential for spread and naturalisation in all southern states.
Various cultivars have been selected over the past 4000 years for either fibre or THC production. Fibre cultivars grow to 6-7 metres and have a strongly lignified stem and low THC contents. The high THC varieties are much smaller and often referred to as Cannabis indica. Ingestion or inhalation of the smoke leads to euphoria which is followed by depression. Habitual use or high dosages leads to physical debility, cancers and claims of genetic disorders. Use is often associated with schizophrenia but it is unclear whether it is causal. The hallucinogenic properties and long term negative effects have been recorded in Chinese herbals from the first or second century.

Distribution:

ACT, NSW, QLD, SA, TAS, VIC, WA.

Courtesy Australia's Virtual Herbarium.

Habitats:

Prefers full sun and warm temperatures.

Climate:

Sub humid to humid temperate and tropical.

Soil:

Prefers well drained fertile soils.

Plant Associations:

Significance:

Beneficial:

Oils, medicinal, food. Fibre for rope, string, bags, nets and paper.

Detrimental:

Weed of streams, open and disturbed areas, roadsides and fence lines.
Illicit drug made from the dried leaves and smoked or a more refined form from the female heads and their resins.

Toxicity:

Toxic. Mules and horses have been poisoned in Greece.

Symptoms:

Excitation, trembling, sweating, salivation, difficult breathing and death within 15-30 minutes of symptoms showing.

Treatment:

Legislation:

Cultivation and possession is prohibited under drug laws.
Noxious weed of ACT. NSW and Victoria.

Management and Control:

Establishing competitive pastures and grazing usually eliminates Indian Hemp. Hand pulling, mowing and cultivation also provide effective control but require repeating to contain subsequent seedlings.
Many herbicides provide effective control. In non crop areas, away from trees bromacil and tebuthiuron provide good control and residual action to control seedlings for a year or two. Triazines provide good pre emergent control in triazine tolerant crops. Clopyralid (Lontrel®) provides good control of plants less than 600 mm tall in Eucalypt based bushland. Paraquat is often used for a quick knockdown of illicit crops but may cause toxicity if the sprayed crop is subsequently smoked.

Thresholds:

Eradication strategies:

Initial treatment with herbicides followed by hand pulling for a few years is usually effective.

Herbicide resistance:

None reported.

Biological Control:

The Hemp Moth (Cydia sinana) is a potential biocontrol agent for naturalised infestations.

Related plants:

Hops (Humilis lupulus)

Plants of similar appearance:

Kangaroo Apple (Solanum laciniatum and Solanum aviculare) don't have teeth on the leaf margins and have purple flowers with succulent berry fruit.

References:

Auld, B.A. and Medd R.W. (1992). Weeds. An illustrated botanical guide to the weeds of Australia. (Inkata Press, Melbourne). P142. Photo.

Bodkin, F. (1986). Encyclopaedia Botanica. (Angus and Robertson, Australia).

Cunningham, G.M., Mulham, W.E., Milthorpe, P.L. and Leigh, J.H. (1992). Plants of Western New South Wales. (Inkata Press, Melbourne). P209. Photo.

Everist, S.L. (1974). Poisonous Plants of Australia. (Angus and Robertson, Sydney).

Harden, Gwen J. (1991). Flora of NSW. (Royal Botanic Gardens, Sydney). Volume . P. Diagram.

Hussey, B.M.J., Keighery, G.J., Cousens, R.D., Dodd, J. and Lloyd, S.G. (1997). Western Weeds. A guide to the weeds of Western Australia. (Plant Protection Society of Western Australia, Perth, Western Australia). P126.

Lamp, C. and Collet, F. (1990). A Field Guide to Weeds in Australia. (Inkata Press, Melbourne).

Lazarides, M. and Cowley, K. and Hohnen, P. (1997). CSIRO handbook of Australian Weeds. (CSIRO, Melbourne). #193.1.

Moerkerk, M.R. and Barnett, A.G. (1998). More Crop Weeds. R.G. and F.J. Richardson, Melbourne. P75. Diagrams. Photos.

Parsons, W.T. and Cuthbertson, E.G. (1992) Noxious weeds of Australia. (Inkata Press, Melbourne). P369-372. Diagrams, Photos.

Acknowledgments:

Collated by HerbiGuide. Phone 08 98444064 or www.herbiguide.com.au for more information for more information.