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Growing Hemp for CBD: How it Affects THC Production

If you’re looking to get your fields into the hemp game, there is always the question of what type of hemp crop you want to produce. Those chasing the most lucrative crops will quickly find themselves sorting through the essentials for growing hemp for CBD.

With China having sewn up the hemp-fiber market and the rest of Asia throwing in to dominate the grain market, CBD is the primary focus for many American hemp farmers.

Unfortunately, CBD crops are more fickle, legally precarious, and demanding than fiber or grain production fields. A large part of this is due to the relationship between Cannabidiol (CBD) and Tetrahydrocannabinol (THC).

Most states define hemp as a variety of cannabis with a THC concentration of 0.3 percent or less taken from any part of the plant, usually on a dry weight basis.

The road was paved for US farmers to bank in on this distinction when language was put into the 2018 Farm Bill that effectively legalized the cultivation of industrial hemp.

With the bill came permission to transfer hemp-derived products across state lines for commercial or other purposes and does not put restrictions on the sale, transport, or possession of hemp-derived products, so long as those items are produced in a manner in accordance with the law.

And, the balance between THC and CBD is at the heart of most of those legal requirements and deeply seated in the biology of cannabis.

Understanding Cannabis Plants

Cannabis is a dioecious plant, which means that male and female reproductive organs are in separate plants. It’s important that farmers who want to grow hemp for CBD know that CBD is mostly stored in the trichomes, which are abundant in un-pollinated female cannabis flowers.

Male plants produce no commercially viable source of CBD. What’s worse is that pollen from male cannabis plants can significantly impact the CBD production of female plants, dropping their output by as much as 50%.

The reason for this drop is that energy used to create flowers, and thus CBD, is diverted by fertilized females to seed production.

What to Plant for CBD Production

When considering the planting seeds there are some very important considerations to take into account. At the top of the list is whether you will be planting feminized seeds or regular seeds. As you may have guessed, regular seed is significantly less expensive to purchase as an input, often sold between $1,000 and $10,000 per pound. The disadvantage to planting regular seeds for CBD is that about half the plants that germinate will end up being males. These male plants are liabilities to CBD farmers because they can pollinate flowers on the surrounding female plants. This pollination results in heavy seeding which will dramatically reduce CBD production per acre. In order to prevent the issues that male plants cause farmers can manually search out and pull males plants from the field. This is not an easy task and it must be performed during the magic window of time between the moment plants reveal their sex and when they first begin casting pollen into the breeze. Planting regular seeds significantly reduces your chances for a high-yield CBD harvest. Feminized seeds on the other hand are produced to germinate almost entirely as female seedlings. Feminized seeds are sold in a wide price range that often exceeds $1/seed. Farmers planting feminized seeds will save on the headaches caused by regular hemp seeds.

When purchasing feminized seeds it is very important to be diligent in confirming that the seeds have been tested and verified to meet or exceed the claims associated with them.

Many hemp farmers plant their fields with high-quality female clones, ensuring every plant is pulling its weight when it comes time to harvest. This is the most costly method up front, but it is also the method that ensures you have a living field of female plants ready for the growing season.

The best clones are from hand-selected mother plants that possess the most desirable characteristics, including vigorous growth, strong plant structure, abundant flowering potential and powerful CBD-to-THC ratios.

THC vs CBD production

Two, tightly linked genes are what separate hemp and marijuana. Both of these genes convert precursor cannabinoid, CBGa. One turns it into the acidic form of THC and the other turns it into the acidic form of CBD.

When the genes to produce THC are turned on, the one to produce CBD is turned off, allowing for the production of recreational and medical marijuana. When both genes are turned on, the plants produce a less psychoactive combination, as CBD potentially lessens the effects of THC.

Of course, for those growing hemp for CBD, the goal is to have the CBD production genes turned on and the THC genes turned off, yielding legal, high-quality CBD oil.

Various growing conditions and additional factors can impact the levels of CBD and THC. In cases were a hemp farmer’s crops end up testing above 0.3% THC by weight, the crop is considered failed — or “hot.”

A farmer is required by law to destroy their hot crops, which can be financially detrimental.

One of the best ways to avoid ending up with a hot crop is by using seed varieties that have passed statewide THC validation and observation trials. Another option is to plant clones where the mother plants were grown in local conditions, as these will pose the least risk.

Growing Indoors or Outdoors

The primary advantage to the cultivation of hemp for CBD outdoors is that it has substantially lower starting costs. This is particularly the case if you already have the necessary farming equipment, such as a transplanter.

The primary disadvantage — outside of potential issues with CBD levels in the plants — is the labor necessary to harvest the crop. The key to making outdoor harvesting of CBD crops as efficient as possible is by planting 4’ x 4’ rows with about 6’ to 8’ between rows.

For an outdoor operation, you should expect to have about 1,000 to 1,600 plants grown per acre, each of which will need to be tended to individually — hence the labor-intensive aspect of growing hemp for CBD.

With indoor cultivation, you have total control over the environment, which means substantially reduced risks of contamination. However, the artificial lighting required means a hefty upfront cost.

Final Thoughts — Growing Hemp for CBD: How it Affects THC Production

For farmers chasing the most lucrative of hemp crops, there is no way to go but by targeting CBD. However, the integral relationship between CBD and THC production makes it the most legally precarious of the potential hemp products to grow.

Rarely do you read about grain or fiber crops being labeled “hot” and being destroyed by law. CBD crops, on the other hand, walk the line as farmers push to keep the CBD production gene turned on and THC gene turned off.

The best solution for farmers wanting to focus on CBD is to take advantage of the various benefits of certified and tested female clones. These clones will give you the best idea of the exact plant you’re growing — daughter like mother — and will give you an all-female crop, preventing you from dealing with the lower yield caused by unproductive male plants pollinating flowers and diverting resources away from CBD production.

Fallon Hanley

View posts by Fallon Hanley
Fallon boasts 15 years of experience in growing and breeding cannabis and hemp, and managing grows.