Each industrial hemp variety has its own set of characteristics: small or large seed; higher or lower oil content; different oil composition, etc. Varieties grown for fiber may contain from 15%-25% of bast fibres. As markets develop, contracts to grow industrial hemp may specify the exact varieties that will be grown to meet specific market needs.
Industrial hemp varieties tested in Ontario to date have all been of European origin, with the exception of new Ontario-bred varieties such as Anka and Carmen. They come in 2 types: Dioecious, which have male and female flower parts on separate plants (e.g., Kompolti and Unico B), and Monoecious, which have male and female flower parts on the same plant (e.g., Ferimon and Futura). A third type of cultivar, known as Female Predominant, is a dioecious type that has 85%-90% female plants. It is believed this type can produce a higher yield of grain. Most French varieties are hybrid populations of predominantly female types.
Only varieties of industrial hemp that are named in the List of Approved Cultivars, published by Health Canada, are approved for planting in Canada. These varieties are known to produce plants containing less than 0.3% THC under normal conditions. The THC level may vary with stage of growth and increase under environmental stress conditions. They mature to fibre in 60-90 days and to grain in 110-150 days. Using home grown or “common” seed is illegal.
Dual Purpose Cultivars
Most of the French and Romanian cultivars are suitable for both grain and fibre production. These tall cultivars present some challenges for harvesting. Growers need also to consider that weather conditions after grain harvest (late August or September) may not be suitable for retting and drying of the stalks. The FIN 314 variety, which will grow to a maximum height of 0.9 m (36 in.), and other short stalked grain types (1-1.5 m) are not suitable for dual production. Industry trends seem to be moving toward specific grain or fibre varieties.