Light Deprivation Greenhouses: The Best Solution for Unwanted Pollination

hand holds cannabis plant inside light deprivation greenhouse

A real sense of concern is brewing among outdoor cannabis and hemp growers about stray pollination ruining their crops.

That's why concerned outdoor growers have started to look into newer and better greenhouses to protect their crops from the elements, pests, and the risk of hermaphroditic pollen. The most serious growers will turn to light deprivation greenhouses because they allow you to produce multiple yields per year.

Marijuana vs Hemp

While marijuana and hemp are grown differently and used for different purposes, they share the same botanical genus and species, Cannabis sativa. Because they are both technically 'cannabis plants,' for the sake of clarity, the variant grown for medicinal and recreational consumption will be referred to as marijuana and the variant grown for fiber, seed, and oil, with .3 percent or less THC, as hemp.

Hemp has been used for thousands of years for fiber, clothing, food, and oil.  George Washington grew hemp, the first American flag was made out of hemp, and hemp was a strategic military resource for the U.S. Army as late as World War II.

It was this botanical similarity that caused hemp to be outlawed along with its psychoactive-cousin in 1937. But, recently, hemp and marijuana have been legalized in many states allowing farmers in states like Oregon to grow hemp for fiber and oil.

Grow for the Oil, Good for the Soil

Farmers in states with legalized cannabis sometimes prefer to grow industrial hemp because they don't need new machinery to farm it and if used as a rotation crop, hemp will not deplete the topsoil.

The Oregon Department of Agriculture issues licenses for hemp growers as the industry is veering away from industrial uses and toward the more lucrative market of medical marijuana products.

ODA director of Market Access & Certification, Lindsay Eng said "There's a lot of interest in CBD extraction with hemp," and, "It's allowed. It just has to be .3 percent THC or lower. Given Western Oregon's good climate and the high price of land, it's probably the most marketable [in contrast to industrial hemp]. There's absolutely a huge difference in profitability."

It is precisely this .3 percent THC limit that has growers of both hemp and marijuana worried about cross-pollination.

 Cross-Pollination Risks to Marijuana

The risks associated with cross-pollination are well known in the hemp and marijuana growing industries. In the last four years, the Oregon court system has been littered with nuisance pollination cases.

Southern Oregon has a dense population of pot growers, and they have a well-founded fear of cross-pollination by hemp grows. If cross-pollination happens, it would degrade the THC content and the marijuana would lose most of its value.

Pollen from a male hemp plant can cause the plants to produce seeds instead of buds ruining a female-only, sinsemilla cannabis crop.

Risks to Hemp

Of course, hemp farmers can face cross-pollination too, as a recent court case in Polk county Oregon demonstrates. In this case, where both the plaintiff and the defendant are hemp farmers, the plaintiff asserts that:

"Cross-pollination is a significant risk in the hemp growing industry. There are two specific risks. First, male plants that contain higher THC levels can pollinate female hemp plants that originally contain low THC levels. The resulting seeds produce plants with highest levels than the original female plant, which means the resulting plants also have lower amounts of CBD and CBG. Second, pollinated female plants may produce both male and female seeds. Female seeds are more desirable because female plants are grown to full maturity and harvested at the end of the season, whereas male plants die off shortly after pollination."

Don't Expect the State's Help

As for cross-pollination fears between hemp and marijuana, Lindsey Eng from the Oregon Department of Agriculture says, "There's nothing in our rules or statute about that. We don't have the authority to regulate it. We think they should co-exist. ... Landowners will figure it out on their own. It's a civil matter."

Although some states have contemplated instituting distinct zones for marijuana and hemp to assuage fears of cross-pollination, as of now, no state has adopted a zoning policy.

Cannabis growers need to take an active role in protecting their crops from damaging pollen. Right now, new technology in light deprivation greenhouses promises the best protection from pollen and the potential for multiple yields.

 What is a Light Deprivation Greenhouse?

Light deprivation, sometimes called 'light-depo' or 'light-dep,' is a growing technique that simulates different seasonal changes by adjusting the amount of light (and darkness) that the plants receive.  Light deprivation greenhouses cover the plants in a blackout material to mimic the autumn season and trick the cannabis plants into initiating the flowering stage.

Having this control over the flowering stage allows cannabis growers to enjoy multiple harvests per year and reduces the time needed for maturity.

Why Are They Superior?

Well, to be honest, not all light deprivation greenhouses are created equally. Most low-tech greenhouses are not fully sealed or filtered, meaning they only offer a modicum of protection from wayward pollen. They may rely on simple temperature probes to power fans, and analog timers for blackout systems.

Whereas, the best systems using the latest technology, let growers run sealed light deprivation greenhouses (that cover an entire acre) using HEPA filtration, UVC flashers, and Air ionizers to prevent pollen from entering the greenhouse. The technology also kills mold spores before they have a chance to spread.

Either way, using any light deprivation greenhouse will offer marijuana and hemp growers protection from damaging pollen and spores while giving them the potential to pull three turns a year without crazy equipment. That, my friends, sounds like a win-win-win.