State legislatures have taken action to promote industrial hemp as an agricultural commodity in recent years. A wide range of products, including fibers, textiles, paper, construction and insulation materials, cosmetic products, animal feed, food, and beverages all may use hemp. The plant is estimated to be used in more than 25,000 products spanning nine markets: agriculture, textiles, recycling, automotive, furniture, food/nutrition/beverages, paper, construction materials and personal care.
One of the reasons hemp fiber has been valued is because of its length. The primary bast fibers in the bark are 5–40 mm long, and are amalgamated in fiber bundles which can be 1–5 m long (secondary bast fibers are about 2 mm long). The woody core fibers are short—about 0.55 mm—and like hardwood fibers are cemented together with considerable lignin. The core fibers are generally considered too short for high grade paper applications (a length of 3 mm is considered ideal), and too much lignin is present. While the long bast fibers have been used to make paper almost for 2 millennia, the woody core fibers have rarely been so used. Nevertheless it has been suggested that the core fibers could be used for paper making, providing appropriate technology was developed (de Groot et al. 1998). In any event, the core fibers, have found a variety of uses, as detailed below. The long, lignin-poor bast fibers also have considerable potential to be used in many non-paper, non-textile applications, as noted below.
In the UK, the Department for Environment, Food and Rural Affairs treats hemp as a purely non-food crop, but with proper licensing and proof of less than 0.2% THC concentration, hemp seeds can be imported for sowing or for sale as a food or food ingredient. In the U.S., imported hemp can be used legally in food products and, as of 2000, was typically sold in health food stores or through mail order.
Hemp is grown in temperate zones as an annual cultivated from seed and can reach a height of up to 5 metres (16 feet). Crops grow best in sandy loam with good drainage and require average monthly rainfall of at least 65 mm (2.5 inches) throughout the growing season. Crops cultivated for fibre are densely sowed and produce plants averaging 2–3 metres (6–10 feet) tall with almost no branching. Plants grown for oilseed are planted farther apart and are shorter and many-branched. The slender stalks are hollow except at the tip and base. The leaves are compound with palmate shape, and the flowers are small and greenish yellow. Seed-producing flowers form elongate, spikelike clusters growing on the pistillate, or female, plants. Pollen-producing flowers form many-branched clusters on staminate, or male, plants. Maximum yield and quality are obtained by harvesting soon after the plants reach maturity, indicated by the full blossoms and freely shedding pollen of the male plants. Although sometimes pulled up by hand, plants are more often cut off about 2.5 cm (1 inch) above the ground.