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Species: Cannabis sativa L.
French: Chanvre; English: Hemp; Spanish: Cáñamo; German: Hanf.
Origin and diffusion
Hemp (Cannabis sativa L.) is a textile fiber plant (from vegetative organs) native to the northern and southern regions of the Himalayas. Its use dates back to the Neolithic period and China is the country where it has been cultivated for the longest time. Its introduction in Europe probably dates back to the second millennium BC. In Italy it is reported in the first century BC, but it is only in the Middle Ages that it finds a certain diffusion, especially in the Po Valley. In the twentieth century, after having recorded a progressive increase in the cultivated area up to the 1930s, its surface has gradually decreased. Today it is grown on a few hectares. Worldwide it is mainly grown in Asia (China and India), Eastern Europe and Russia.
Indian Canana (Cannabis indica) (originally from Kafiristan, south of Hindukush) provides very mediocre fiber. In the East it is cultivated for the extraction of some drugs: lhascisc is extracted from the flowered ends, while the dry leaves form the bhang. This species is of short stature, with vinous shades, leaves tending to be alternate, very narrow and long leaf segments, very small and dark seeds. The whole plant has a contracted, leafy appearance and a very intense green color (from Herbaceous crops by Franco Angelini - SO.GRA.RO. - Roman Graphic Society of Rome).
Hemp in Padula (SA)
Hemp seeds (photo website)
Hemp is an annual species, with taproot root and erect stem, more or less branched, robust, at first full then hollow, up to 4 meters high. The leaves are mainly opposite, petiolate, palmatosette, with 3-9 lanceolate, sharp, serrated, pubescent segments. It is generally a dioecious species, presenting male and female inflorescences on different plants. The male flowers are gathered to form inflorescences, called panicles, placed in the axillary position, while the female ones are paired, always in the axillary position, but in correspondence with the two stipules, small, sharp and deciduous. The fruit is an achene, commonly called hemp seed or hemp. The shape is commonly ovoid, but sometimes almost spherical. The color is not uniform, but it is more or less speckled, thanks to a network of vascular bundles located under the skin of the pericarp. Brown predominates, sometimes olive or reddish, but there are lighter, whitish and greenish fruits. It contains a single seed, enclosed in a thin pericarp with a horny, indehiscent, bivalve consistency (weight 1.000 seeds equal to 20-22 grams).
Hemp manages to adapt to the most varied environments, even if the best production results are obtained in humid areas and with temperatures of 20-25 ° C throughout the cycle and in clayey and fertile soils.
The genetic improvement (done in the past also in Italy) has led to the creation of varieties with a high percentage of fiber.
As a renewal crop, it requires deep plowing and subsequent refinement of the soil shortly before sowing. The sowing, late April-early May, is done in rows 15-18 cm apart, in order to obtain, at harvest, an investment of 100-200 plants per square meter, which can be reached using about 60 kg / ha of seed. From a nutritional point of view, hemp is very sensitive to nitrogen fertilization: the lack of this element leads to a significant reduction in the development of the plant. To obtain a good production it is necessary to add 150 kg / ha of nitrogen, 150 kg / ha of phosphorus and 100 kg / ha of potassium. Normally, irrigation is unnecessary in the North. As far as weeds are concerned, hemp, once the emergency phase is over, does not present any problems because it has a very rapid development and shows a high competitiveness.
Collection and use
If the collection only concerns the rod, it is carried out in correspondence with the female flowering (first half of August); if the production of achenes is also to be obtained, it is postponed to the end of September. At one time the harvest was done by hand; today it is mechanized, also due to the fact that hemp is now used for products other than those of the past. In fact, for the preparation of special papers, the green rod is used, which undergoes the scouring process to separate the wooden part, or canapulo, from the fiber. A good production of green rod is equal to 120-150 quintals per hectare. The fiber obtained (12-15 quintals) is used for the manufacture of fabrics, filters and thermo-acoustic insulators. From female plants the seed (up to 15 quintals per hectare) can also be used, used for the extraction of oil used for the production of colors and paints. The material that remains from the sculling can be used as bedding, while the extraction panels are used in zootechnical feeding.
Adversity and pests
The wind is a fearsome enemy of hemp because, especially if strong, it can damage the bark following mutual rubbing of the stems or, in extreme cases, break them; if the plants are still in the early stages, they can be subject to lodging phenomena.
Rain, if violent, can cause the plant to break or lie in its early stages of development.
Hailstones, if light, can open wounds and predispose to fungal diseases; if violent, they often cause deep lacerations, with consequent depreciation of the fiber, or even the breaking of the stems.
Late frost can easily damage young seedlings.
Drought affects the production and quality of the product.
These include a parasitic phanerogam, their banks (Orobanche ramosa L.), the most harmful parasite of hemp, and some fungi, such as Peronoplasmopara cannabina (Ott.) Peglion., Agent of downy mildew, Dendrophoma marconii Cav., Agent of the powdery mildew, and Sclerotinia libertiana Fuck, agent of the disease of the sclerotia.
Malicious insects include crickets (Gryllulus desertus Pall. And Gryllulus chinensis Webb.), Beetle (Melolontha melolontha L.), hemp laphid (Phorodon cannabis Pass.) And alticica (Psylliodes attenuata Koch.).