RE: Seeds16 Jan 2020 16:01
....'Cannabis is what’s known as a dioecious species, meaning that male and female flowers are borne on separate plants. There are some monoecious varieties of cannabis with male and female flowers on the same plant, and stress can also induce the production of male flowers on female plants, but these are exceptions to the plant’s normally dioecious nature. Flowering is induced when day and night lengths become equal. Male cannabis plants flower for a period of two to four weeks, and a single male flower can produce 350,000 pollen grains. Pollen is carried to female plants on the wind and can travel great distances when conditions are favorable. Bees will collect cannabis pollen but are generally not attracted to the female flowers to contribute to pollination.
In the 1970s, marijuana growers found that preventing pollination by rogueing out male plants or producing only females (through clonal propagation or sowing of feminized seed) could greatly increase the yield and potency of their crop. This works because cannabis is one of the few plant species that can actively increase the number and size of its female sex organs in response to prolonged virginity, according to Small and Naraine, 2016. The longer female plants go unpollinated, the more flowers are produced and the larger they get.
Cannabinoids, including the valuable end products THC and CBD, are concentrated in the female flower tissue. A study by Meier and Mediavilla, 1998, found that pollination decreased the yield of essential oils in cannabis flowers by 56%. Today, most marijuana is sinsemilla (Spanish for “without seeds”) and seeded crops are considered inferior, commanding a lower price in the marketplace. The same strategy is now also being applied by industrial hemp growers producing CBD.
Industrial hemp grown for grain or fiber is a different story. Male plants and pollen are required to create hemp grain used for food, feed and oil. Fiber hemp does not require pollination, but the prohibitive cost of planting feminized seed or female clones means that fiber fields will usually include male plants. As a result, the recent introduction of hemp grown for grain and fiber in Michigan increases the risk of pollination for marijuana and CBD hemp growers. I say that industrial hemp increases rather than creates this risk because cannabis pollen has been blowing across the Midwest long before 2019'
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