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Editor's note: The following article is the last of a three-part series featuring the marketing and agronomic considerations involved in growing hemp for cannabidiol – CBD – production. 

Pollen drift is a significant risk factor in production of hemp for cannabidiol. Farmers plant feminized seed and cull male plants because cannabidiol content plummets when a female plant is pollinated. A reasonable expectation for cannabidiol content as a percentage of dry weight is more than 8 percent.

When female flowers are pollinated cannabidiol can decline by 4 percent. Beyond reducing saleable product, growers would be unlikely to find a buyer for hemp biomass with just 4 percent cannabidiol content.

Pollen can travel as much as 10 miles. Susan Candee, a farmer from southern Wisconsin, said she drove a radius of 20 miles around her farm to see what other farmers were growing. Hemp was once grown in Wisconsin and large populations of the plant remain. Before deciding to grow hemp for cannabidiol growers should look for wild-hemp populations and other forms of hemp production in their areas. If risks are too great, they may need to grow hemp inside a greenhouse or find other solutions to prevent pollen drift.

Testing for tetrahydrocannabinol is required for every variety of hemp from every field. The test costs $250 for each variety. A farmer also must notify his or her state 30 days before harvest. The crop must be destroyed if it contains more than 0.3 percent tetrahydrocannabinol.

Choosing proper seed genetics is the first way to keep plants from “going hot.” The second step is to provide ideal growing conditions. That’s because hemp produces tetrahydrocannabinol in response to stress. Overfeeding phosphorus and potassium will put plants at greater risk of crossing the tetrahydrocannabinol threshold. Every variety will eventually pass the threshold if it’s left in the field too long.

While the state of Wisconsin requires just a single pre-harvest test, Candee said she wanted to test tetrahydrocannabinol levels to mitigate risk. Crop insurance will be available in 2020 for hemp growers. But the U.S. Department of Agriculture has stated that hemp with tetrahydrocannabinol exceeding the compliance level won’t constitute an insurable cause of loss.

Harvest critical to production

Harvest is one of the most important aspects of hemp production. If it's harvested and dried incorrectly the crop can be destroyed. Left to grow a hemp plant will produce just one flower. Cannabidiol is produced in the trichomes – or glandular hairs – on the surface of female flowers. By continually topping plants a grower can induce bushing to produce more flowers.

Flowers are ready to harvest when trichomes change from clear white to a milkier-white color, Leah Sandler says. She's the education director and a research agronomist at Michael Fields Agricultural Institute. She’s evaluating which cultivars work best in Wisconsin. Harvest times will differ by variety, planting date and day length. But harvest will generally be conducted from mid-September to mid-October in the Upper Midwest.

Growers can harvest the entire plant, just the flowers or trimmed flowers. Cannabidiol content as a percentage of biomass will be least with harvest of the entire plant and most with trimmed flowers. Growers should talk with buyers about cannabidiol-percentage requirements or requirements for what form harvest must take. Some buyers require a minimum of 8 percent cannabidiol.

Cannabidiol flowers are usually harvested by hand. Cannabidiol content can be drastically reduced if there isn’t enough labor to harvest hemp in a timely fashion. Poor harvest timing also increases the risk of surpassing the tetrahydrocannabinol threshold. Large-scale growers can invest in tractor attachments for harvesting and removing flowers from stalks.

Harvested hemp should be dried as quickly as possible. Ventilation and humidity control are important. Heat can degrade cannabidiol so fans are recommended. Ideal conditions for drying hemp are between 60 degrees and 70 degrees Fahrenheit and 60 percent humidity. If there’s too much moisture the crop can quickly mold.

Hemp should be dried under a roof and away from direct sunlight. Drying facilities must be clean and free of animals, birds and insects. Hemp-drying machines can aid in the process.

Certified-organic cannabidiol products must be derived from a certified-organic crop that’s processed at a certified-organic facility. It may be difficult to find certified-organic processors to extract cannabidiol. But several are now in the process of certification.

Because certifiers regulate federal law they can’t certify products allowed in some states but not allowed federally. They may be wary of certifying cannabidiol products because of their murky federal legal status. Some won’t certify cannabidiol as a food product or food ingredient. But some will certify it as long as the label isn’t making a health claim or has a disclaimer noting the product hasn’t been evaluated by the U.S. Food and Drug Administration.

Seed treatments can be an issue in organic production. Kristen Adams, certification-team lead at the Midwest Organic Services Association, said there are two commonly used substances that can be applied to hemp to produce feminized seed. The first is colloidal silver. It’s allowed if it can be verified as natural. The second is gibberellic acid, which is allowed in organic production.

Growers would spray with either substance when plants start to flower. Spraying stops production of the male chromosome and results in feminized seed. Seed isn’t considered treated for certification purposes because the plant is treated before it produces seed. As long as harvested seed isn’t treated with other prohibited substances, organic growers can plant the feminized seed produced with either substance.

To produce certified-organic feminized seed a grower would need to use feminized pollen from a gibberellic-acid treatment to pollinate a certified-organic mother plant. Organic growers also would need to conduct an organic-seed search to show it wasn’t available as organic.

There are more questions than answers about growing and marketing hemp for cannabidiol production. The Midwest may be best suited to hemp-fiber production because it may be too humid for growing other kinds of hemp. Or pollen from wild hemp may make it impossible to grow hemp for cannabidiol outdoors. The market for cannabidiol products could be a fad and price could plummet as demand declines. Or it could be the next major cash crop for Midwestern farmers.

There are many challenges and a lot is left to learn. But if growers can successfully grow hemp and participate in equitable supply chains, hemp for cannabidiol could transform rural communities.

The preceding article was originally published by the Midwest Organic and Sustainable Education Service's "Organic Broadcaster."

Visit mosesorganic.org or michaelfields.org for more information.

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Chuck Anderas is an organic specialist working with the Midwest Organic and Sustainable Education Service. Call 888-906-6737 for more information.