3 Ways to Prevent Your Hemp Harvest From Growing Hot

Features - Hot Hemp

The best way to prevent ‘hot hemp’ is to choose cultivars that will test below the federal threshold of 0.3% THC. But keeping the heat off requires so much more, experts say.

July 10, 2020

Illustrations by Britt Spencer

The Agriculture Improvement Act of 2018 (the 2018 Farm Bill) might have legalized hemp nationwide, but the law had an ulterior motive. One of Congress’ motivations was to help farmers across the United States cash in on the skyrocketing global demand for cannabidiol, or CBD—one of the naturally occurring chemical compounds that can be extracted from the tall, fibrous hemp crop.

Hemp is a variety of the Cannabis sativa L. plant that has been used for thousands of years to produce everything from clothing to building materials. While hemp can still be a viable cash crop for all these purposes, the real money-maker for many U.S. farmers today is CBD.

CBD is reported to offer many of the same natural health benefits as the tetrahydrocannabinol (THC) found in cannabis, just without the mind-altering effects. (In other words: THC gets you high; CBD doesn’t.) Because of this, products that contain CBD are popping up everywhere—in oils, lotions, bath salts, beverages, pet food and more. Restaurants are now even selling meals prepared with CBD.

But the law, while decidedly pro-CBD, does not make profiting from CBD an easy proposition. If the U.S. Department of Agriculture’s interim final rule implementing the 2018 Farm Bill goes into effect as drafted, farmers with hemp that contains more than 0.3% THC in state-administered tests must pay to destroy their crops in addition to losing the potential commercial value of the plants.

Unfortunately for the nascent U.S. hemp industry, failed tests are fast becoming the norm. From Florida to Washington state, farmers who had intended to grow hemp with high concentrations of CBD are actually inadvertently growing what the federal government classifies as illegal marijuana (plants containing more than 0.3% THC)—or, to the hemp industry, “hot hemp.”

In Hawaii, the Honolulu Star-Advertiser reported in August 2019 that 18 crops—more than half of the hemp crops cultivated for the state’s pilot program—were unusable due to high THC levels.

In the here and now, crops are testing hot—and the rush to grow CBD-rich hemp may be causing the problem.

Meanwhile, the Wisconsin Department of Agriculture, Trade and Consumer Protection (DATCP) said about 12% of hemp field tests came back hot for the 2019 growing season. The percentage of hot hemp didn’t change from 2018 to 2019 even though the number of registered growers increased tenfold. The regional newspaper Isthmus also reported that two Wisconsin growers anticipated a complete loss of about $40,000 on a crop of 70 hemp plants that tested at 0.5% THC content.

All told, Vote Hemp estimates that only about 50% to 60% of the hemp planted in 2019 will be harvested because of “crop failure, non-compliant crops and other factors.”

Why is this happening?

For one thing, scientific research methods, seed-certification processes and regional farming know-how are all still developing. In time, a hot crop will likely be a statistical outlier as the industry figures out how to perfect the low THC/high CBD balance, experts tell Hemp Grower. But in the here and now, crops are testing hot—and the rush to grow CBD-rich hemp may be causing the problem.

“The biggest factor contributing to the issue of hot hemp is probably the genetics that growers are sourcing,” says Bob Pearce, Ph.D., a professor of agronomy at the University of Kentucky who helps lead the school’s hemp research program. “Cultivars that produce predominantly CBD also produce small amounts of THC, typically in a pretty consistent ratio for that cultivar. So, as CBD increases, so does THC. Then you throw in environmental stress and management on top of a marginally compliant cultivar, and you start to see problems with hot hemp.”

Hemp experts have offered their top three recommendations for growers looking to seize the CBD future while preventing their crops from running hot.

“A lot of growers are going to struggle to reach 10% or higher CBD and 0.3% THC if they continue with current strains and practices.” — Jeanine Davis, professor, Department of Horticultural Science, North Carolina State University

1. Choose Known Cultivars.

Hemp growers should select known cultivars that have consistently tested well below 0.3% THC in their local areas, Pearce says. In most cases, the reason hemp tests hot is because of bad genetics. Farmers in Kentucky, for instance, might be using seeds bred for West Coast soil and climate when what they really need are cultivars developed specifically for Kentucky.

However, choosing a proven low-THC cultivar has its drawbacks. Pearce says some cultivars that have tested below 0.3% THC also produce less CBD—roughly 2% to 5% by his estimates. Most growers are aiming for 10% CBD. Pearce acknowledges the trade-off but says it’s better to have a legal plant with less CBD than a destroyed crop.

The most important thing, he stresses, is to obtain seeds and plants from reputable sources so growers have “some assurance they are getting what was advertised.” One problem, though, Pearce warns, is that seed and plant certification programs for hemp are currently in their “infancy at best and non-existent at worst.”

While many states have approved lists of hemp seeds, these are far from sure bets—at least not yet. Leeann Duwe, a spokeswoman for the Wisconsin DATCP, says the state of Wisconsin precertifies hemp seeds through a lab analysis of the variety. The DATCP looks for the total THC or the ability to calculate the total THC. If the THC is below 0.3%, then the variety is approved. However, the state’s approval of a seed variety does not guarantee a plant will pass a preharvest test for THC levels, Duwe tells Hemp Grower.

In Canada, where the industrial hemp market is more established (since legalization under the Cannabis Act in 1998), the Industrial Hemp Licensing Unit of Health Canada publishes a list of approved cultivars for each growing season. (At press time, the 2020 list was not available, but the 2019 list can be found here: http://bit.ly/Canada-approved-cultivars.)

Jeanine Davis, Ph.D., associate professor in the Department of Horticultural Science at North Carolina State University, says she expects to see more self-testing take place over the next year as a result of the Farm Bill and hot tests. Farmers want to do what they can to make sure they avoid a hot test.

“A lot of growers are going to struggle to reach 10% or higher CBD and 0.3% THC if they continue with current strains and practices,” she says. “What I saw in the western part of North Carolina in 2018 and 2019 is growers selecting strains that would produce the highest CBD possible and that would test at 0.3% total THC for the official test. If THC went above 0.3% at harvest, they weren’t too concerned because ... they had buyers.” Even though they had buyers, however, possession of hemp that exceeds the 0.3% threshold at any point is considered illegal. (For more on CBD to THC ratios, read "Cornell University Breaks Ground on Hemp Research.")

The new proposed federal rules push the time for official testing at a lab registered by the Drug Enforcement Administration (DEA) 15 days prior to anticipated harvest time, which makes a big difference in THC levels. “So same rules, just new time frame for when the official testing needs to take place,” Davis says.

“With the publishing of the interim federal hemp rule, we will see a big change in the strains growers choose to grow,” Davis says. “Many of the strains produced now will not test out at 0.3%15 days before harvest.”

The good news is that the hot hemp problem is spurring research and development in new cultivars. In one example, the Spanish company Hemp Trading and the Spanish university UPV claim they have developed the first entirely THC-free hemp variety with high cannabigerol (CBG), a cannabinoid that can be extracted from both cannabis and hemp plants for medical use. (CBG can be found early during a hemp plant’s growth and is later converted into different chemical structures. CBD and THC start as CBG.)

This is promising, to be sure, but there are multiple variables during the growing process that can impact THC levels—even if you choose the right seeds.

All told, Vote Hemp estimates that only about 50% to 60% of the hemp planted in 2019 will be harvested because of “crop failure, non-compliant crops and other factors.”

2. Pay Attention to the Soil.

Preventing hot hemp is not only about selecting the right plant and the botany of that plant; it’s also about the biology of the soil and the enzymes converting the CBG to CBD, says Michael Goodenough, a managing partner of D&G Agtek, the parent company of sweetheal.com, a hemp and CBD producer in Connecticut.

“When the cannabis plant has been grown naturally in healthy living soils without stress, the CBG converts to CBD,” Goodenough says. “Living soils...naturally convert the sand, silt, clay and organic matter into nutrients that the plant can control and uptake as it desires. By allowing the plant to control this process, we see increases in all the sought-after cannabinoids and terpenes, including the minor ones we have yet to fully understand. This also helps prevent the undesired production of THC, increases the plant’s own natural defenses, creates less work for the farmer and, in turn, makes it less risky to grow.”

Goodenough notes that hemp in the U.S. is often grown on land that used to grow other crops, and the soil may have been neglected for years, especially if the farm went bankrupt.

Through his work, Goodenough has helped develop remediation processes that he says could take hemp with high THC content and then convert it into other cannabinoids like CBD.

3. Harvest Early.

In addition to paying attention to the soil, Goodenough says growers should also rethink taking their plants to full term. Cannabinoids increase with time in the plant, which is why growers should consider employing an in-house testing protocol and be prepared to harvest before the THC levels exceed 0.3%, even though harvesting early results in lower CBD levels as well.

“One thing farmers need to start thinking about is the ideal harvest time to maximize what they’re growing for but also to minimize risk,” says Kyle Sosebee, J.D., a hemp and cannabis lawyer based in Massachusetts. “We know that THC spikes at the very end of the growing season along with a lot of the other cannabinoids. What we may end up seeing is farmers harvesting earlier than they otherwise would just so they have a bigger safety margin and avoid that end-of-the-season spike in THC.

"That may become part of the growing strategy for farmers: They’re going to short themselves on CBD, but it’s going to be better than a total crop loss if your entire crop goes hot.”

Paul Barbagallo is a Boston-based writer and a former senior editor for Bloomberg News and beat reporter for Bloomberg BNA.