Selection for fiber has resulted in strains that have much more bark fiber tissues and much less woody core than encountered in narcotic strains, oilseed strains, and wild plants (Fig. 12). In non-fiber strains of Cannabis, bark can be less than one quarter of the stem tissues (i.e. more than three quarters can be woody core). By contrast, in fiber strains half of the stem tissues can be bark, and more than half of this can be the desirable long primary fibers (de Meijer 1995). Non-fiber strains rarely have as much as 15% fiber in the bark.
Low concentrations of CBD aren’t the only concern, either. Cannabis plants are hardy and tough, and their thick stalks possess a special property: bioremediation. When grown in contaminated soil, hemp plants absorb heavy metals and other chemical waste, effectively cleansing the terrain. While all plants absorb some chemicals from the soil, the structure, size, and genetic makeup of hemp make it especially adept at this task. Cannabis is so effective that crops of industrial hemp were planted in the aftermath of the 1986 Chernobyl disaster to help purify heavily irradiated soil. When hemp stalks are used for fiber, paper, and other nonconsumptive industrial purposes, the contaminants absorbed into the plants pose no threat to humans.
Cannabis plants produce a unique family of terpeno-phenolic compounds called cannabinoids, some of which produce the "high" which may be experienced from consuming marijuana. There are 483 identifiable chemical constituents known to exist in the cannabis plant, and at least 85 different cannabinoids have been isolated from the plant. The two cannabinoids usually produced in greatest abundance are cannabidiol (CBD) and/or Δ9-tetrahydrocannabinol (THC), but only THC is psychoactive. Since the early 1970s, Cannabis plants have been categorized by their chemical phenotype or "chemotype", based on the overall amount of THC produced, and on the ratio of THC to CBD. Although overall cannabinoid production is influenced by environmental factors, the THC/CBD ratio is genetically determined and remains fixed throughout the life of a plant. Non-drug plants produce relatively low levels of THC and high levels of CBD, while drug plants produce high levels of THC and low levels of CBD. When plants of these two chemotypes cross-pollinate, the plants in the first filial (F1) generation have an intermediate chemotype and produce intermedite amounts of CBD and THC. Female plants of this chemotype may produce enough THC to be utilized for drug production.
"The data supporting efficacy and dosing are specific to one product: Epidiolex," Bonn-Miller says. "That's not necessarily translatable to 'Joe Bob's CBD Blend.'" A CBD extract you buy online or in a dispensary will almost certainly have less CBD in it, he explains, and will contain other cannabinoids—meaning that it will work differently and will need to be dosed differently. "This is not to say that 'Joe Bob's CBD Blend' definitely isn't going to be effective for pediatric epilepsy, but it means that we need to study it before we know."
Though use of marijuana among Washington state youth has remained relatively stable over the last several years (see Healthy Youth Survey), youth perception of harm from use of marijuana has been steadily decreasing (meaning: fewer adolescents believe marijuana use is harmful). Marijuana is the second most-commonly used substance among 12th graders (alcohol is the first), with 27% of high school seniors reporting current (past 30-day) use.
Hemp does best on a loose, well-aerated loam soil with high fertility and abundant organic matter. Well-drained clay soils can be used, but poorly-drained clay soils are very inappropriate because of their susceptibility to compaction, which is not tolerated. Young plants are sensitive to wet or flooded soils, so that hemp must have porous, friable, well-drained soils. Sandy soils will grow good hemp, provided that adequate irrigation and fertilization are provided, but doing so generally makes production uneconomical. Seedbed preparation requires considerable effort. Fall plowing is recommended, followed by careful preparation of a seedbed in the spring. The seedbed should be fine, level, and firm. Seed is best planted at 2–3 cm (twice as deep will be tolerated). Although the seedlings will germinate and survive at temperatures just above freezing, soil temperatures of 8°–10°C are preferable. Generally hemp should be planted after danger of hard freezes, and slightly before the planting date of maize. Good soil moisture is necessary for seed germination, and plenty of rainfall is needed for good growth, especially during the first 6 weeks. Seeding rate is specific to each variety, and this information should be sought from the supplier. Fiber strains are typically sown at a minimum rate of 250 seeds per m2 (approximately 45 kg/ha), and up to three times this density is sometimes recommended. In western Europe, seeding rates range from 60–70 kg/ha for fiber cultivars. Recommendations for seeding rates for grain production vary widely, from 10–45 kg/ha. Densities for seed production for tall, European, dual-purpose cultivars are less than for short oilseed cultivars. Low plant densities, as commonly found in growing tall European cultivars for seed, may not suppress weed growth adequately, and under these circumstances resort to herbicides may pose a problem for those wishing to grow hempseed organically. Hemp requires about the same fertility as a high-yielding crop of wheat. Industrial hemp grows well in areas that corn produces high yields. Growing hemp may require addition of up to 110 kg/ha of nitrogen, and 40–90 kg/ha of potash. Hemp particularly requires good nitrogen fertilization, more so for seed production than fiber. Adding nitrogen when it is not necessary is deleterious to fiber production, so that knowledge of the fertility of soils being used is very important. Organic matter is preferably over 3.5%, phosphorus should be medium to high (>40 ppm), potassium should be medium to high (>250 ppm), sulfur good (>5,000 ppm), and calcium not in excess (<6,000 ppm).