In 1938, the Popular Mechanics Magazine referred Hemp as the “new million-dollar crop” as its plant parts can be used in manufacturing a range of products from cellophane to dynamite. Hemp is cultivated for its fiber, seeds, and resin. The plant was first domesticated for fiber. In recent years, hemp seed is used for extracting oil – used in cooking and cosmetics. Resin from the plant is used in medicines and in insect repellants.
Hemp is an annual, dioecious (male and female flowers are produced on the different plants), dimorphic (male and female plants have differences), and is a highly cross-pollinated crop. There are some cultivars of hemp that are monoecious. Its laterally branched tap root system extracts nutrients and water from deep inside the soil profile. Hence, the plant is known to be grown in most climates and requires minimal care. It is currently grown in China, Europe, Russia, Canada and some parts of the U.S. Hemp plants can grow up to 1-5 meters depending upon the growing conditions and their genetic makeup. Its stems are erect, usually branched with woody interiors and hollow internodes. However, for fiber, relatively unbranched stems with long internodes are preferred. Whereas for oil, short plants with low to no branching, and early maturity cultivars are preferred. The density of planting can determine branching, plant height, seed formation, and other cultivation practices in hemp plants.
Hemp, scientifically known as Cannabis sativa, belongs to the same family of marijuana. Hemp plants have cannabinoids in various parts of the plant in varying concentrations. Of the 120 different types of cannabinoids, few are psychoactive as Delta-9 Tetrahydrocannabinol (THC), but others are non-psychoactive such as cannabidiol (CBD), and cannabinol (CBN). Hemp belongs to those group of cannabis genus that contains less than 0.03% THC a level determined to distinguish between marijuana and Hemp. However, CBD, a non-psychotic cannabinoid is in higher concentrations in Hemp and is reported to have medicinal value. The cannabinoids are synthesized in special epidermal glands that are found in various parts of the plant but particularly abundant in female reproductive organs, the flowers, making the flower the most economical part of the plant for medicinal value.
Cultivation of cannabis plants, including Hemp, was banned under the Marijuana Tax Act of 1938 in the U.S. As a result, there are negligible genetic resources of Hemp in the US to assist with the growing modern uses. The traits of interest are fiber length, fiber quality, cannabinoid profile and content, day length sensitivity, and pest and disease resistance. Moreover, hemp being a highly cross-pollinated crop, controlling male plant flowering to maintain elite traits with controlled pollination is one of the growing research needs. Research programs at some universities are focusing on evaluating current hemp varieties for fiber yield, quality, and cannabinoid content. According to the 2018 Farm Bill, Industrial Hemp is now an agricultural crop which opens opportunities for states across the U.S. to pursue research in this long-forgotten crop.