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Hemp (from Old English hænep) is a commonly used term for high-growing varieties of the Cannabis plant and its products, which include fiber, oil, and seed. Hemp is refined into products such as hemp seed foods, hemp oil, wax, resin, rope, cloth, pulp, paper, and fuel.
Other variants of the herb Cannabis sativa are widely used as a drug, commonly known as marijuana. These variants are typically low-growing and have higher content of tetrahydrocannabinol (THC). The legality of Cannabis varies widely from country to country, and from state to state in the United States. In many countries regulatory limits for concentrations of psychoactive drug compounds, particularly THC, in hemp require the use of strains of the plant which are bred for low content.
Hemp is used for many varieties of products including the manufacture of cordage of varying tensile strength, durable clothing and nutritional products. The bast fibers can be used in 100% hemp products, but are commonly blended with other organic fibers such as flax, cotton or silk, for apparel and furnishings, most commonly at a 55%/45% hemp/cotton blend. The inner two fibers of hemp are more woody and are more often used in non-woven items and other industrial applications, such as mulch, animal bedding and litter. The oil from the fruits ("seeds") oxidizes (commonly, though inaccurately, called "drying") to become solid on exposure to air, similar to linseed oil, and is sometimes used in the manufacture of oil-based paints, in creams as a moisturizing agent, for cooking, and in plastics. Hemp seeds have been used in bird seed mix as well. A survey in 2003 showed that more than 95% of hemp seed sold in the EU was used in animal and bird feed.
In modern times hemp is used for industrial purposes including paper, textiles, clothing, biodegradable plastics, construction (as with Hempcrete and insulation), body products, health food and bio-fuel.
In a new development hemp is being processed relatively inexpensively into electrodes possibly even more efficient than graphene for use in supercapacitors.
Hemp seeds can be eaten raw, ground into a meal, sprouted, made into hemp milk (akin to soy milk), prepared as tea, and used in baking. The fresh leaves can also be consumed in salads. Products include cereals, frozen waffles, hemp milk ice cream, hemp tofu, and nut butters. A few companies produce value added hemp seed items that include the seed oils, whole hemp grain (which is sterilized by law in the United States, where they import it from China and Canada), dehulled hemp seed (the whole seed without the mineral rich outer shell), hemp flour, hemp cake (a by-product of pressing the seed for oil) and hemp protein powder.
Within the UK, the Department for Environment, Food and Rural Affairs (Defra) has treated hemp as purely a non-food crop. Seed appears on the UK market as a legal food product, and cultivation licenses are available for this purpose. In North America, hemp seed food products are sold, typically in health food stores or through mail order. The United States Department of Agriculture has concluded that "the market potential for hemp seed as a food ingredient is unknown. However, it probably will remain a small market, like those for sesame and poppy seeds." Since 2007 the commercial success of hemp food products has grown considerably.
|Typical nutritional analysis|
of hulled hemp seeds
|Calories/100 g||567 kcal|
|Oleic 18:1 (Omega-9)||5.8|
|Linoleic 18:2 (Omega-6)||27.6|
|Linolenic 18:3 (Omega-3)||8.7|
|Gamma-Linolenic 18:3 (Omega-6)||0.8|
|Vitamin A (B-Carotene)||4.0 IU/100g|
|Thiamine (Vit B1)||1.4 mg|
|Riboflavin (Vit B2)||0.3 mg|
|Pyridoxine (Vit B6)||0.1 mg|
|Vitamin C||1.0 mg|
|Vitamin E||9.0 IU/100g|
Approximately 44% of the weight of hempseed is edible oils, containing about 80% essential fatty acids (EFAs); e.g., linoleic acid, omega-6 (LA, 55%), alpha-linolenic acid, omega-3 (ALA, 22%), in addition to gamma-linolenic acid, omega-6 (GLA, 1–4%) and stearidonic acid, omega-3 (SDA, 0–2%). Proteins (including edestin) are the other major component (33%). Hempseed's amino acid profile is comparable to other sources of protein such as meat, milk, eggs and soy.
Protein Digestibility Corrected Amino Acid Score values, which measure the degree to which a food for humans is a "complete protein", were 0.49-0.53% for whole hemp seed, 0.46-0.51% for hemp seed meal, and 0.63-0.66% for dehulled hemp seed. Hemp proteins thus have a PDCAAS equal to or greater than certain grains, nuts, and some legumes. Soy protein, by comparison, has a PDCAAS value of 1.0.
Hemp oil, like any food oil rich in essential fatty acids, will spontaneously oxidize and turn rancid within a short period of time if not stored properly; Its shelf life is extended when stored in a dark airtight container and refrigerated.
Hemp fiber has been used extensively throughout history, with production climaxing soon after being introduced to the New World. Items ranging from rope, to fabrics, to industrial materials were made from hemp fiber. Hemp was often used to make sail canvas, and the word canvas derives from cannabis. Today, a modest hemp fabric industry exists, and hemp fibers can be used in clothing. Pure hemp has a texture similar to linen.
Concrete-like blocks made with hemp and lime have been used as an insulating material for construction. Such blocks are not strong enough to be used for structural elements; they must be supported by a brick, wood, or steel frame. However hemp fibres are extremely strong and durable and have been shown to be used in replacement of wood for many jobs including creating very durable and breathable homes.
The first example of the use of hempcrete was in 1986 in France with the renovation of the Maison de la Turque in Nogent-sur-Seine by the innovator Charles Rasetti. In the UK hemp lime was first used in 2000 for the construction of two test dwellings in Haverhill. Designed by Modece Architects, who pioneered hemp's use in UK construction, the hemp houses were monitored in comparison with other standard dwellings by BRE. Completed in 2009, The Renewable House is one of the most technologically advanced made from hemp-based materials. The first US home made of hemp-based materials was completed in August 2010 in Asheville, North Carolina.
A panellized system of hemp-lime panels for use in building construction is currently under test in a European Union funded research collaboration lead by the University of Bath. The panels are being designed to assure high quality construction, rapid on-site erection, optimal hygrothermal performance from day one and energy and resource efficient buildings. The 36 month long work programme aims to refine product and manufacturing protocols, produce data for certification and marketing, warranty, insurance cover and availability of finance. It also includes the development of markets in Britain, France and Spain.
Hemp is used as an internal plaster and is a mixture of hemp hurd (shive) mixed with larger proportions of a lime based binder. Hemp plaster has insulative qualities.
Concrete block made with hemp in France
A mixture of fibreglass, hemp fiber, kenaf, and flax has been used since 2002 to make composite panels for automobiles. The choice of which bast fiber to use is primarily based on cost and availability. Various car makers are beginning to use hemp in their cars, including Audi, BMW, Ford, GM, Chrysler, Honda, Iveco, Lotus, Mercedes, Mitsubishi, Porsche, Saturn, Volkswagen and Volvo. For example, the Lotus Eco Elise and the Mercedes C-Class both contain hemp (up to 20 kg in each car in the case of the latter).
The first identified coarse paper, made from hemp, dates to the early Western Han Dynasty, two hundred years before the nominal invention of papermaking by Cai Lun, who improved and standardized paper production using a range of inexpensive materials, including hemp ends, approximately 2000 years ago. Recycled hemp clothing, rags and fishing nets were used as inputs for paper production.
The Saint Petersburg, Russia paper mill of Goznak opened in 1818. It used hemp as its main input material. Paper from the mill was used in the printing of "bank notes, stamped paper, credit bills, postal stamps, bonds, stocks, and other watermarked paper."
In 1916, U.S. Department of Agriculture chief scientists Lyster Hoxie Dewey and Jason L. Merrill created paper made from hemp pulp and concluded that paper from hemp hurds was "favorable in comparison with those used with pulp wood." Modern research has not confirmed the positive finding about hemp hurds. They are only 32% and 38% cellulose. On the other hand, hemp contains only 4-10% lignin against the 18-30% found in wood. This lignin must be removed chemically and wood requires more use of chemicals in the process. The actual production of hemp fiber in the U.S continued to decline until 1933 to around 500 tons/year. Between 1934-35, the cultivation of hemp began to increase but still at a very low level and with no significant increase of paper from hemp.
Hemp has never been used for commercial high-volume paper production due to its relatively high processing cost. Currently there is a small niche market for hemp pulp, for example as cigarette paper. Hemp fiber is mixed with fiber from other sources than hemp. In 1994 there was no significant production of 100% true hemp paper. World hemp pulp production was believed to be around 120,000 tons per year in 1991 which was about 0.05% of the world's annual pulp production volume. The total world production of hemp fiber had in 2003 declined to about 60,000 from 80,000 tons. This can be compared to a typical pulp mill for wood fiber, which is never smaller than 250,000 tons per annum. The cost of hemp pulp is approximately six times that of wood pulp, mostly because of the small size and outdated equipment of the few hemp processing plants in the Western world, and because hemp is harvested once a year (during August) and needs to be stored to feed the mill the whole year through. This storage requires a lot of (mostly manual) handling of the bulky stalk bundles. Another issue is that the entire hemp plant cannot be economically prepared for paper production. While the wood products industry uses nearly 100% of the fiber from harvested trees, only about 25% of the dried hemp stem — the bark, called bast — contains the long, strong fibers desirable for paper production. All this accounts for a high raw material cost. Hemp pulp is bleached with hydrogen peroxide, a process today also commonly used for wood pulp.
Around the year 2000, the production quantity of flax and hemp pulp total 25000-30000 tons per year, having been produced from approximately 37000-45000 tonnes fibers. Up to 80% of the produced pulp is used for specialty papers (including 95% of cigarette paper). Only about 20% hemp fiber input goes into the standard pulp area and are here mostly in lower quality (untreated oakum high shive content added) wood pulps. With hemp pulp alone, the proportion of specialty papers probably at about 99%. The market is considered saturated with little or no growth in this area.
Hemp jewelry is the product of knotting hemp twine through the practice of macramé. Hemp jewelry includes bracelets, necklaces, anklets, rings, watches and other adornments. Some jewelry features beads made from glass, stone, wood and bones. The hemp twine varies in thickness and comes in a variety of colors. There are many different stitches used to create hemp jewelry, however, the half knot and full knot stitches are most common.
Hemp rope was used in the age of sailing ships, though the rope had to be protected by tarring, since hemp rope has a propensity for breaking from rot, as the capillary effect of the rope-woven fibers tended to hold liquid at the interior, while seeming dry from the outside. Tarring was a labor-intensive process, and earned sailors the nickname "Jack Tar". Hemp rope was phased out when Manila, which does not require tarring, became widely available. Manila is sometimes referred to as Manila hemp, but is not related to hemp; it is abacá, a species of banana.
Hemp shives are the core of the stem, hemp hurds are broken parts of the core. In the EU, they are used for animal bedding (horses, for instance), or for horticultural mulch. Industrial hemp is much more profitable if both fibers and shives (or even seeds) can be used.
Hemp can be used as a "mop crop" to clear impurities out of wastewater, such as sewage effluent, excessive phosphorus from chicken litter, or other unwanted substances or chemicals. Eco-technologist Dr. Keith Bolton from Southern Cross University in Lismore, New South Wales, Australia, is a leading researcher in this area. Hemp is being used to clean contaminants at the Chernobyl nuclear disaster site. This is known as phytoremediation - the process of clearing radioisotopes as well as a variety of other toxins from the soil, water, and air.
Hemp, because of its height, dense foliage and its high planting density as a crop, is a very effective and long used method of killing tough weeds in farming by minimizing the pool of weed seeds of the soil. Using hemp this way can help farmers avoid the use of herbicides, to help gain organic certification and to gain the benefits of crop rotation per se. Due to its rapid, dense growth characteristics, in some jurisdictions hemp is considered a prohibited noxious weed, much like Scotch Broom. It has been used extensively to kill weeds in agriculture.
Biofuels, such as biodiesel and alcohol fuel, can be made from the oils in hemp seeds and stalks, and the fermentation of the plant as a whole, respectively. Biodiesel produced from hemp is sometimes known as "hempoline".
Filtered hemp oil can be used directly to only power diesel engines. In 1892, Rudolf Diesel invented the diesel engine, which he intended to fuel "by a variety of fuels, especially vegetable and seed oils, which earlier were used for oil lamps, i.e. the Argand lamp."
Production of vehicle fuel from hemp is very small. Commercial biodiesel and biogas is typically produced from cereals, coconuts, palmseeds and cheaper raw materials like garbage, wastewater, dead plant and animal material, animal feces and kitchen waste.
Hemp is usually planted between March and May in the northern hemisphere, between September and November in the southern hemisphere. It matures in about three to four months.
Millennia of selective breeding have resulted in varieties that look quite different. Also, breeding since circa 1930 has focused quite specifically on producing strains which would perform very poorly as sources of drug material. Hemp grown for fiber is planted closely, resulting in tall, slender plants with long fibers. "Until the early 1900s industrial hemp was a valuable crop used all over the world for its strong fibers and oil seeds. Today, however, the common perception of the industrial hemp plant is generally negative and associated with the drug marijuana. This perception is the legacy of a century of powerful influences constructing hemp as a dangerous drug, even though it is not a drug and it has the potential to be a profitable alternative crop. In the United States, the public's perception of hemp as marijuana has blocked hemp from becoming a useful crop and product," in spite of its vital importance prior to World War II. Ideally, according to Britain's Department for Environment, Food and Rural Affairs, the herb should be desiccated and harvested towards the end of flowering. This early cropping reduces the seed yield but improves the fiber yield and quality. In these strains of industrial hemp the tetrahydrocannabinol (THC) content would have been very low.
The seeds are sown from mid April to mid May with grain drills to 4–6 cm sowing depth. Hemp needs less fertilizer than corn does. A total of 60–150 kg of nitrogen, 40–140 kg phosphorus (P2O5) and 75–200 kg of potassium  per acre for hemp fiber made before sowing and again later, maybe three to four weeks. When practiced, especially in France double use of fiber and seed fertilization with nitrogen doses up to 100 kg / ha rather low. Organic fertilizers such as manure can utilize industrial hemp well. Neither weeds nor crop protection measures are necessary.
A total of 46 varieties of hemp with low levels of tetrahydrocannabinol (THC) are certified by the European Union (EU). They have, unlike other types, a very high fiber content of 30-40%. In contrast to cannabis for medical use, varieties grown for fiber and seed have less than 0.2% THC and they are unsuitable for producing hashish and marijuana. The most important cannabinoid in industrial hemp is cannabidiol (CBD) with a proportion of 1 to 5%.
Cannabis sativa L. subsp. sativa var. sativa is the variety grown for industrial use, while C. sativa subsp. indica generally has poor fiber quality and is primarily used for recreational and medicinal purposes. The major difference between the two types of plants is the appearance and the amount of Δ9-tetrahydrocannabinol (THC) secreted in a resinous mixture by epidermal hairs called glandular trichomes, although they can also be distinguished genetically. Oilseed and fiber varieties of Cannabis approved for industrial hemp production produce only minute amounts of this psychoactive drug, not enough for any physical or psychological effects. Typically, hemp contains below 0.3% THC, while cultivars of Cannabis grown for recreational use can contain anywhere from 2% to over 20%.
Smallholder plots are usually harvested by hand. The plants are cut at 2 to 3 cm above the soil and left on the ground to dry. Mechanical harvesting is now common, using specially adapted cutter-binders or simpler cutters.
The cut hemp is laid in swathes to dry for up to four days. This was traditionally followed by retting, either water retting (the bundled hemp floats in water) or dew retting (the hemp remains on the ground and is affected by the moisture in dew, and by molds and bacterial action). Modern processes use steam and machinery to separate the fiber, a process known as thermomechanical pulping.
For profitable hemp farming, particularly deep, humus-rich, nutrient-rich soil with controlled water flow is preferable. Water logged acidic, compressed or extremely light (sandy) soils primarily affect the early development of plants. Steep slopes and high altitudes of more than 400 m above sea level are best avoided. Hemp is relatively insensitive to cold temperatures and can withstand frost down to -5 degrees C. Seeds can germinate down to 1-3 degrees. Hemp needs a lot of heat, so earlier varieties come to maturation. The water requirement is 300-500 l / kg dry matter. Up to 3 feet growing roots into the soil can also use water supplies from deeper soil layers. Worth noting is that the water requirement of hemp is at least 14 times lower than that of cotton which takes between 7 000-29 000 l/kg, according to WWF.
Hemp benefits crops grown after it. For this reason it is generally grown before winter cereals. Advantageous changes are high weed suppression, soil loosening by the large hemp root system and the positive effect on soil tilth. Since hemp is very self-compatible, it can also be grown several years in a row in the same fields (monoculture).
Hemp plants can be vulnerable to various pathogens, including bacteria, fungi, nematodes, viruses and other miscellaneous pathogens. Such diseases often lead to reduced fiber quality, stunted growth, and death of the plant. These diseases rarely affect the yield of a hemp field, so hemp production is not traditionally dependent on the use of pesticides.
Hemp is considered by a 1998 study in Environmental Economics to be environmentally friendly due to a decrease of land use and other environmental impacts, indicating a possible decrease of ecological footprint in a US context compared to typical benchmarks. A 2010 study, however, that compared the production of paper specifically from hemp and eucalyptus concluded that "industrial hemp presents higher environmental impacts than eucalyptus paper"; however, the article also highlights that "there is scope for improving industrial hemp paper production". Hemp is also claimed to require few pesticides and no herbicides, and it has been called a carbon negative raw material. Results indicate that high yield of hemp may require high total nutrient levels (field plus fertilizer nutrients) similar to a high yielding wheat crop.
The world-leading producer of hemp is China, with smaller production in Europe, Chile and North Korea. Over thirty countries produce industrial hemp, including Australia, Austria, Canada, Chile, China, Denmark, Egypt, Finland, France, Germany, Great Britain, Hungary, India, Italy, Japan, Korea, Netherlands, New Zealand, Poland, Portugal, Romania, Russia, Slovenia, Spain, Sweden, Switzerland, Thailand, Turkey and Ukraine.
The United Kingdom and Germany resumed commercial production in the 1990s. British production is mostly used as bedding for horses; other uses are under development. Companies in Canada, the UK, the United States and Germany, among many others, process hemp seed into a growing range of food products and cosmetics; many traditional growing countries still continue to produce textile-grade fibre.
Air dry stem yields in Ontario have from 1998 and onward ranged from 2.6-14.0 tonnes of dry, retted stalks per hectare (1-5.5 t/ac) at 12% moisture. Yields in Kent County, have averaged 8.75 t/ha (3.5 t/ac). Northern Ontario crops averaged 6.1 t/ha (2.5 t/ac) in 1998. Statistic for the European Union for 2008 to 2010 say that the average yield of hemp straw has varied between 6.3 and 7.3 ton per ha. Only a part of that is bast fiber. Approximately one tonne of bast fiber and 2-3 tonnes of core material can be decorticated from 3-4 tonnes of good quality, dry retted straw. For an annual yield of this level is it in Ontario recommended to add nitrogen (N):70–110 kg/ha, phosphate (P2O5): up to 80 kg/ha and potash (K2O): 40–90 kg/ha. The average yield of dry hemp stalks in Europe was 6 ton/ha (2.4 ton/ac) in 2001 and 2002.
In the Australian states of Tasmania, Victoria, Queensland and, most recently, New South Wales, the state governments have issued licences to grow hemp for industrial use. The state of Tasmania pioneered the licensing of hemp in 1990. The state of Victoria was an early adopter in 1998, and has reissued the regulation in 2008.
Hemp production in tonnes 2003–2004
|China||23000||79 %||24000||79 %|
|France||4300||15 %||4300||14 %|
|Chile||1250||4 %||1250||4 %|
|Russia||200||1 %||300||1 %|
|Turkey||150||1 %||150||< 1%|
|Ukraine||150||1 %||150||< 1%|
|Romania||100||< 1 %||100||< 1%|
|Hungary||40||< 1 %||40||< 1%|
|Poland||15||< 1 %||15||< 1%|
|Spain||8||< 1 %||8||< 1%|
|Serbia||2||< 1 %||2||< 1%|
|Total||29215||100 %||30315||100 %|
Queensland has allowed industrial production under licence since 2002, where the issuance is controlled under the Drugs Misuse Act 1986. Most recently, New South Wales now issues licences under a law, the Hemp Industry Regulations Act 2008 (No 58), that came into effect as of 6 November 2008.
Commercial production (including cultivation) of industrial hemp has been permitted in Canada since 1998 under licenses and authorization issued by Health Canada (9,725 ha in 2004, 5450 ha in 2009). It is expected that hemp will contribute $100 million to Canada's economy.
France is Europe's biggest producer with 8,000 hectares cultivated. 70-80% of the hemp fibre produced in Europe in 2003 was used for specialty pulp for cigarette papers and technical applications. About 15% is used in the automotive sector and 5-6% were used for insulation mats. Approximately 95% of hurds were used as animal bedding, while almost 5% were used in the building sector. In 2010/2011, a total of 11 000 ha was cultivated with hemp in the EU, a decline compared with previous year.
|This section requires expansion. (August 2012)|
Some Russian speaking people have created a web site on topics related to growing cannabis.
In the United Kingdom, cultivation licences are issued by the Home Office under the Misuse of Drugs Act 1971. When grown for non-drug purposes, hemp is referred to as industrial hemp, and a common product is fibre for use in a wide variety of products, as well as the seed for nutritional aspects and for the oil. Feral hemp or ditch weed is usually a naturalized fibre or oilseed strain of Cannabis that has escaped from cultivation and is self-seeding.
Hemp is not legal to grow in the U.S. under Federal law because of its relation to marijuana, and any imported hemp products must meet a zero tolerance level. It is considered a controlled substance under the Controlled Substances Act (P.L. 91-513; 21 U.S.C. 801 et seq.). Some states have made the cultivation of industrial hemp legal, but farmers in North Dakota, Hawaii, Kentucky, Maine, Maryland, Oregon, California, Montana, West Virginia and Vermont have not yet begun to grow it because of resistance from the federal Drug Enforcement Administration. In 2013, after the legalization of marijuana in the state, several farmers in Colorado planted and harvested several acres of hemp, bringing in the first hemp crop in the United States in over half a century. Colorado, Vermont, California, and North Dakota have passed laws enabling hemp licensure. All four states are waiting for permission to grow hemp from the DEA. Currently, North Dakota representatives are pursuing legal measures to force DEA approval. Oregon has licensed industrial hemp as of August 2009[update]. In February 2014, Congress passed an agriculture bill that eased restrictions on cultivation in 10 states.
Hemp is one of the earliest domesticated plants known. It has been cultivated by many civilizations for over 12,000 years. Hemp use archaeologically dates back to the Neolithic Age in China, with hemp fiber imprints found on Yangshao culture pottery dating from the 5th millennium BC. The Chinese later used hemp to make clothes, shoes, ropes, and an early form of paper. The classical Greek historian Herodotus (ca. 480 BC) reported that the inhabitants of Scythia would often inhale the vapors of hemp-seed smoke, both as ritual and for their own pleasurable recreation.
Textile expert Elizabeth Wayland Barber summarizes the historical evidence that Cannabis sativa, "grew and was known in the Neolithic period all across the northern latitudes, from Europe (Germany, Switzerland, Austria, Romania, Ukraine) to East Asia (Tibet and China)," but, "textile use of Cannabis sativa does not surface for certain in the West until relatively late, namely the Iron Age." "I strongly suspect, however, that what catapulted hemp to sudden fame and fortune as a cultigen and caused it to spread rapidly westwards in the first millennium B.C. was the spread of the habit of pot-smoking from somewhere in south-central Asia, where the drug-bearing variety of the plant originally occurred. The linguistic evidence strongly supports this theory, both as to time and direction of spread and as to cause."
Jews living in Palestine in the 2nd century were familiar with the cultivation of hemp, as witnessed by a reference to it in the Mishna (Kil'ayim 2:5) as a variety of plant, along with Arum, that sometimes takes as many as three years to grow from a seedling. In late medieval Germany and Italy, hemp was employed in cooked dishes, as filling in pies and tortes, or boiled in a soup. Hemp in later Europe was mainly cultivated for its fibers, and was used for ropes on many ships, including those of Christopher Columbus. The use of hemp as a cloth was centered largely in the countryside, with higher quality textiles being available in the towns.
The Spaniards brought hemp to the Western Hemisphere and cultivated it in Chile starting about 1545. However, in May 1607, "hempe" was among the crops Gabriel Archer observed being cultivated by the natives at the main Powhatan village, where Richmond, Virginia is now situated; and in 1613, Samuell Argall reported wild hemp "better than that in England" growing along the shores of the upper Potomac. As early as 1619, the first Virginia House of Burgesses passed an Act requiring all planters in Virginia to sow "both English and Indian" hemp on their plantations. The Puritans are first known to have cultivated hemp in New England in 1645.
George Washington pushed for the growth of hemp and even grew hemp himself, as it was a cash crop commonly used to make rope and fabric. In May 1765 he noted in his diary about the sowing of seeds each day until mid-April. Then he recounts the harvest in October which he grew 27 bushels that year.
There is some speculation that George Washington smoked the flower of the cannabis plant in order to achieve a recreational high, but there is no evidence in any of his writings that he grew hemp for anything other than industrial purposes. It is sometimes supposed that an excerpt from Washington's diary, which reads "Began to seperate [sic] the Male from the Female hemp at Do.&—rather too late" is evidence that he was trying to grow female plants for the THC found in the flowers. However, the editorial remark accompanying the diary states that "This may arise from their [the male] being coarser, and the stalks larger"  In subsequent days, he describes soaking the hemp (to make the fibers usable) and harvesting the seeds, suggesting that he was growing hemp for industrial purposes, not recreational.
George Washington also imported the Indian Hemp plant from Asia, which was used for fiber and, by some growers, for intoxicating resin production. In a letter to William Pearce who managed the plants for him Washington says, "What was done with the Indian Hemp plant from last summer? It ought, all of it, to be sown again; that not only a stock of seed sufficient for my own purposes might have been raised, but to have disseminated seed to others; as it is more valuable than common hemp."
In 1937, the Marihuana Tax Act of 1937 was passed in the United States. It levied a tax on anyone who dealt commercially in cannabis, hemp, or marijuana. The reasons that hemp was also included in this law are disputed—several scholars have claimed that the Act was passed in order to destroy the US hemp industry, with the primary involvement of businessmen Andrew Mellon, Randolph Hearst, and the Du Pont family.
One claim is that Hearst believed that his extensive timber holdings were threatened by the invention of the decorticator, which he feared would allow hemp to become a very cheap substitute for the paper pulp that was used in the newspaper industry. Modern science suggests that this fear would have been unfounded. Improvements of the decorticators in the 1930s, machines that separate the fibers from the hemp stem, could not make hemp fiber a very cheap substitute for fibers from other sources due to the fact that the long strong fibers are only found in the bast, the outer part of the stem. Only about 1/3 of the stem are long and strong fibers.
Another claim is that Mellon, Secretary of the Treasury and the wealthiest man in America at that time, had invested heavily in DuPont's new synthetic fiber, nylon, and believed that the replacement of the traditional resource, hemp, was integral to the new product's success.
The Marihuana Tax Act of 1937 was ruled unconstitutional by the Supreme Court in a unanimous verdict decided in Leary v. United States, and ultimately superseded by the Controlled Substances Act of 1970.
Hemp was used extensively by the United States during World War II. Uniforms, canvas, and rope were among the main textiles created from the hemp plant at this time. Much of the hemp used was cultivated in Kentucky and the Midwest. During World War II, the U.S. produced a short 1942 film, Hemp for Victory, promoting hemp as a necessary crop to win the war.
Hemp has been grown for millennia in Asia and the Middle East for its fibre. Commercial production of hemp in the West took off in the eighteenth century, but was grown in the sixteenth century in eastern England. Because of colonial and naval expansion of the era, economies needed large quantities of hemp for rope and oakum. Other important producing countries were China, North Korea, Hungary, the former Yugoslavia, Romania, Poland, France and Italy.
In Western Europe, the cultivation of hemp was not legally banned by the 1930s, but the commercial cultivation stopped by then, due to decreased demand compared to increasingly popular artificial fibres. Theories about the potential for commercial cultivation of hemp in very large quantities have been strongly criticized by European experts on Hemp such as Dr. Hayo M.G. van der Werf and Dr. Ivan Bûcsa. From their perspective hemp was, outside the U.S, simply out-competed by other fibers in most applications.
From the 1950s to the 1980s, the Soviet Union was the world's largest producer (3,000 km² in 1970). The main production areas were in Ukraine, the Kursk and Orel regions of Russia, and near the Polish border. Since its inception in 1931, the Hemp Breeding Department at the Institute of Bast Crops in Hlukhiv (Glukhov), Ukraine, has been one of the world's largest centers for developing new hemp varieties, focusing on improving fiber quality, per-hectare yields, and low THC content.
In Japan, hemp was historically used as paper and a fiber crop. There is archaeological evidence cannabis was used for clothing and the seeds were eaten in Japan back to the Jōmon period (10,000 to 300 BCE). Many Kimono designs portray hemp, or asa (Japanese: 麻), as a beautiful plant. In 1948, marijuana was restricted as a narcotic drug. The ban on marijuana imposed by the United States authorities was alien to Japanese culture, as the drug had never been widely used in Japan before. Though these laws against marijuana are some of the world's strictest, allowing five years imprisonment for possession of the drug, they exempt hemp growers, whose crop is used to make robes for Buddhist monks and loincloths for Sumo wrestlers. Because marijuana use in Japan has doubled in the past decade, these exemptions have recently been called into question.
The cultivation of hemp in Portuguese lands began around the fourteenth century onwards, it was raw material for the preparation of rope and plugs for the Portuguese ships. Colonies for factories for the production of flax hemp, such as the Royal Flax Hemp Factory in Brazil.
After the Restoration of Independence in 1640, in order to recover the ailing Portuguese naval fleet, were encouraged its cultivation as the Royal Decree of D. John IV in 1656. At that time its cultivation was carried out in Trás-os-Montes, Zone Tower Moncorvo, more precisely in Vilariça Valley, fertile land for any crop irrigation, and a very large area, flat and very fertile culture still wide until the last century grew up tobacco, a plant that needs a large space to expand and grow, the area lies in the valley of Serra de Bornes.
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