Hemp

Family

Cannabaceae

Habit

annual

Height

2.5 m

Spread

0.8 m

Growth

very fast

Lifespan

1 year

First yield

after 1 year

Yield per plant

up to 0 kg

Yield in cultivation

up to 1 t/ha

Energy yield

250 kcal per m² a year

Hardiness

zone 3–10

Shade tolerance

full sun

Soil

Sand, Silt, Loam

Soil moisture

semi-dry – very wet

pH

6 – 7.5

Synonyms

Cannabis

Times apply to the northern hemisphere in a temperate climate and shift with altitude and cultivar.

Edible: The plant's seed is edible raw or cooked, can be roasted as a spice, or made into fried cakes. Although tasty, it's challenging to separate from the shell. Grinding the seed with the shell can lead to a grainy texture. The seed has approximately 27.1% protein, 25.6% fat, 7.4% carbohydrates, and 6.1% ash. Extracting a highly nutritious oil rich in essential fatty acids from the seeds is possible. Plant leaves are utilized in soups and have 0.215% carotene.

Medicinal: Cannabis has been available on prescription in Germany since 2017 and is used for chronic pain, for spasticity in multiple sclerosis, and against nausea and loss of appetite under chemotherapy; the active constituents are above all the cannabinoids THC and CBD from the flower heads of female plants. It is dispensed solely through pharmacies and on medical prescription. Strictly to be distinguished from the medicinal varieties is industrial hemp with less than 0.3 percent THC, grown for fibre and seed, which does not produce this effect. The recorded use is far older: hemp has been listed in Indian and Chinese medicine for millennia, and in European folk medicine poultices of the leaves were held to relieve joint pain — neither with modern evidence of efficacy.

Other uses: A drying oil is obtained from the seeds of the plant for various purposes like lighting, soap production, paints, and varnishes. In regions with moderate climates, the oil is extracted from female plants once the male plants used for fiber production have been collected. Harvesting the seeds from female plants involves shaking the plants to gather the mature seeds, preferably in the early morning when the fruits are plump and the environment is damp to avoid seed loss. The stems are trimmed, and the seeds are either shaken onto tarps or beaten with sticks to extract them. Furthermore, the plant yields a sturdy fiber suitable for making rough fabric, ropes, and other goods. The highest quality fiber is obtained from male plants when they become brown and their flowers bloom. To produce paper, the stems are gathered in autumn, treated by roasting or steaming to eliminate the fibers, then boiled in lye and beaten. The resulting paper has a cream hue. Additionally, the plant acts as a beneficial companion to cabbage and other brassicas by deterring the cabbage white butterfly and emitting a volatile essence that hinders harmful soil microorganisms.

Site: The legal position comes before any question of site. In Germany industrial hemp is permitted only from certified seed of a variety listed in the EU catalogue and below 0.3 percent THC, and the planting must be notified to the federal agricultural authority. The spot must be in full sun and deep-soiled; in partial shade the plants grow spindly. Hemp is dioecious and wind-pollinated and its pollen travels far, so cross-pollination must be expected near flowering stands. In a stand it reaches head height to five metres and shades everything beneath it completely: useful as a summer screen, a problem for neighbouring beds. Its value in rotation is high — the deep taproot loosens compacted soil and the dense canopy suppresses weeds without any herbicide. Care: Sow shallowly from mid-April into May, once the soil reaches about ten degrees; germination follows in three to seven days. Sow densely for fibre and widely for seed — closely spaced plants stay unbranched and slender. Hemp is a heavy feeder and answers generous nitrogen with growth; when growing for seed, ease off towards the end. Water regularly while young, later the deep root carries the plant. No pruning is needed and pests and diseases play little part. Fibre harvest falls in the male flowering, seed harvest in late summer; cut early in the morning in damp air, otherwise the seed shatters.

Sow seeds in the greenhouse during spring. Once seedlings reach sufficient size, transfer them to separate pots and relocate them to their permanent spot in early summer. Seeds germinate effectively at low temperatures, with a minimum threshold of 1°C. Alternatively, seeds can be directly sown outdoors in spring.

Hemp is wind-pollinated and yields no nectar, so as a forage plant in the narrow sense it does not count. Its value lies in pollen and above all in timing: the male plants shed in late summer, when little else is flowering in the farmed landscape, and honeybees and bumblebees then work them deliberately. The US Department of Agriculture pollination report accordingly lists hemp as a pollen source for honeybees and bumblebees, with no nectar value and no pollination requirement of its own. No specialist wild bees are known, and it is not a larval food plant for Central European butterflies or moths. The value of the seed, by contrast, is plain: hemp seed has always been winter food for finches, buntings and tits, and standing crops are stripped by birds in autumn. Structure adds to this — a dense hemp stand is summer cover for ground-nesting birds and small mammals.

Special features: Hemp is likely the oldest cultivated plant, with hemp protein and fat being easily absorbed by humans. Bangladesh translates to hemp-human land, symbolizing its cultural foundation. Various hemp varieties cater to fiber/paper, medicine, and fodder, all depicted on a single map.

Central Asia: probably Kazakhstan and the northern foreland of the Altai. Hemp spread across much of Asia as early as the late Pleistocene and was then carried along by people as one of the oldest crop plants of all — into East Asia and India, into the Near East, and via Scythians and Romans into Europe. Today it grows almost worldwide across temperate and tropical zones, partly in cultivation and partly escaped. No original wild populations remain in Central Europe; what turns up here are cultivated stands and short-lived escapes from birdseed and field crops, mostly on nitrogen-rich ruderal ground. European fibre growing is concentrated in France, which by far holds the largest area, followed by Romania, the Netherlands and Germany.

Hemp is an annual pioneer of open, nutrient-rich ground and behaves ecologically as a strong nitrogen indicator. In its home range it colonises river gravels, alluvial sediments and stony slopes; everywhere else it takes the over-fertilised spots near settlements — rubble sites, manure heaps, track edges, railway land. It needs deep, well-aerated, evenly moist soil without waterlogging and roots down to about 140 centimetres. Light must be unrestricted from the start; in shade the plants stay thin and run up. Growth is unusually plastic: depending on site and stand density the same species stays twenty centimetres low or reaches five metres. Flowering is triggered not by warmth but by night length, and begins only once the dark period exceeds ten to twelve hours.