Cannabis sativa Seeds | Hemp
LATIN NAME: Cannabis sativa
COMMON NAME: Hemp
Plant Profile
Cannabis sativa is an annual with a long history and a complicated legal status, and the plant grown for fibre is not the plant grown for resin. Fibre and grain varieties are tall, thin and fast, reaching three metres in a season with a hollow stem and long internodes. Drug varieties are short, bushy and slow, with dense flower clusters and a heavy coating of resin glands.
The species is wind-pollinated and dioecious, with separate male and female plants, though monoecious varieties exist and are used in fibre crops for uniform maturity. The leaves are palmate with five to nine narrow leaflets, and the stem fibre, the bast, runs in a ring under the bark. Hemp has been grown for rope, sailcloth and paper for at least three thousand years.
Science & Biotechnology
The plant produces more than a hundred cannabinoids, of which delta-9-tetrahydrocannabinol and cannabidiol are the best known. THC is the psychoactive compound and CBD is not, and the two are produced in the same glands as acids that decarboxylate with heat. The ratio between them is genetic, and it is the basis of the legal distinction between hemp and drug cannabis in most jurisdictions, usually drawn at 0.3 per cent THC by dry weight.
Fibre quality depends on harvesting before the stem lignifies. The bast fibres are long, strong and stiff, and they are separated from the woody core, the hurd, by retting, a controlled bacterial decay that dissolves the pectin holding the fibres together. Over-retting weakens the fibre and under-retting leaves it stuck to the hurd, so the timing of the cut and the weather during retting decide the value of the crop.
Uses & Benefits
The fibre goes into rope, canvas, insulation, composites and paper, and the hurd is used for animal bedding, for hempcrete and as a absorbent. The seed is a food, sold shelled as hemp hearts and pressed for an oil rich in linoleic and alpha-linolenic acids, and the pressed cake is a protein feed.
CBD extracts are sold for anxiety, for pain and for sleep, and the evidence is mixed: some trials show a reduction in seizures in specific epilepsy syndromes, while the evidence for anxiety and for chronic pain is weaker and the products are poorly standardised. THC remains a controlled substance in most countries, and the rules on growing, transporting and selling any cannabis material differ sharply between jurisdictions.
Growing from Seed
Sow when the soil has warmed to about 10 degrees, one centimetre deep, and thin to the spacing the crop needs: close for fibre, wide for seed or for flowers. The seed germinates in three to seven days, and the seedling grows fast enough to outcompete most weeds within a month.
The crop wants full sun, moisture and nitrogen, and it responds to density: tight planting produces tall unbranched stems and better fibre. Harvest fibre at flowering, before the seed sets, and grain after the seed is ripe. Check the law before sowing anything, since the permitted THC level, the licence required and the legality of the crop vary by country and by state.
Our Take
An ancient fibre and grain crop with a modern legal tangle around it. Grow it for fibre or for seed only where the crop and the cultivar are permitted.
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