THC in Hemp

There have been many Colorado hemp farmers talking about the THC change in their fields year over year, especially because in our state of Colorado we have some of the highest UV concentrations in the entire country and drastic elevation changes between different farm locations, sometimes with a difference of up to a 5,000 feet!

At Feno we are testing many different hemp strains throughout the entire genome to determine a strains average THC levels as well as any spikes we may see due to certain growing conditions like high elevation and UV. Lots of hemp strains can change their THC and CBD levels drastically just in a couple of generations if not properly controlled, and as you can see this may end up being just as big of a problem for the hemp industry's future as the forecasted pollen contamination issue being currently debated.

Feno Hemp Field (2016)

Higher Elevations Equal Higher THC Production

The main problem most farmers are concerned about each year when growing hemp is the question of whether or not the THC of their hemp crop will be too high, in this case it is usually above 0.3% THC. If the farmer sources the right, stabilized, hemp strains they should not see a THC spike above 0.3%. Now, if they are growing a replanted strain each generation in the same field at higher altitudes and UV zones like that of Colorado, especially areas above 6k feet in elevation, then they will definitely see an increase in THC and all cannabinoids over time.

A good example of this was the 3-year test we did at Feno Seed Bank with our USA Hemp Landrace genome. We kept the seed in those specific high UV, high elevation regions, year after year, which led us to some very interesting results.

For our fields below 6,000 feet in elevation, THC stayed the same as the original USA hemp Landrace at about 0.14% THC where we witnessed some spikes near there 0.2%THC that was based on harsher growing conditions. As for the USA Hemp Landrace fields above 8,000 feet elevation, we noticed a significant change in just two full generations. The original crop in this higher elevation area was 0.18% THC and that was the original P1 landrace generation. The next year, the F1 generation in the same field tested at 0.28% THC and the last generation tested above the legal limit of 0.3%, testing all the way up to 0.4% THC making the crop not useable. We had to destroy the entire crop including seed, flower for CBD, and fiber for testing. All of this potential lost revenue happened because of 1/10th of 1% in THC! So you can see that THC increase can become a major problem if not properly controlled in higher elevation areas.

*Side Note: At this point in our testing, our fields tested that year at 0.24% and 0.28% THC when we had the 0.4% THC field test done by the Colorado Department of Agriculture. Unfortunately, their test results were different then ours at Feno and there was nothing we could do about it.Thankfully, this problem has been fixed, and we now test with over 7 different labs to get an accurate average of our THC levels in our hemp crops.

This was a hard lessoned learned and at a very hard time for us at Feno Seed Bank; however it taught us a very valuable lesson about the entire Hemp genome. To be able to control the legality of a Hemp crop’s THC, the farmer or grower must have a stabilized hemp genome that they replace yearly, or grow in lower elevations and/or lower UV regions. We know that some states will never have this generational increase in THC due to their lower elevations and UV, but those in Colorado and the rest of the South-Western United States, as well as Hawaii, will always have to watch out for this THC issue.

UV Increases THC

Another major factor that plays a roll in the increase of THC within a hemp plant is the Sun’s Ultraviolet Radiation (UV) and also the specialized UVB lights that have been proven to increase a plants THC and resin content. There are some areas around the South-Western United States and mainly in the equatorial zones, which have very large amount of UV from the Sun. This increase in the UV spectrum of light can cause the cannabis genome (both hemp and marijuana,) to increase their potential cannabinoid content and in some cases strictly increase its THC or THCV.

UV high environments in the United States like that of Hawaii and the South-Western United States might be able to cause a hemp variety to start producing higher amounts of THC year after year until its stabilizes above 0.3% THC.

This has become such a large fear that the Hawaiian Department of Agriculture created rules to regulate the genetics bread and supplied in Hawaii. The HDA has decided to start with a “Bahamian Landrace” that they think will be well suited for the Hawaiian climate. Only time and testing will tell if this is true, and Feno will make sure to keep a close eye on this situation as the Hawaiian hemp industry matures.

Cannabinoid Specialized Breeding of Hemp

Now knowing about the increase in THC due to higher elevation or increased UV, we can use this as an upside to our Hemp breeding projects by aiming for breeding higher CBD hemp strains under these unique conditions. With the rise of THC, there is also a rise of all other cannabinoids and can have the same doubling factor as I previously mentioned above. This makes Colorado an excellent state to breed hemp strains high in CBD as long as the THC can be controlled. The easiest way to do this is by starting with a hemp genome that is naturally very low in THC. Some of our genetic projects in this sector started with THC levels lower than 0.1% THC so that we had room to over triple a plants natural cannabinoid production without “testing hot” in THC here in Colorado. Another advantage to this breeding project was that we had the ability to select plants with the lowest THC each generation for 3 generations making the low THC phenotype a stabilized dominant trait within this special R&D breeding project. The long term goal for any hemp breeder should be a consistent THC level under 0.25% THC so that there will never be a possibility of a THC spike due to different phenotypic expressions within different grow environments.

With the chance of a multi-million dollar mistake due to THC problems of a hemp farm, there is a major need for stabilized hemp genetics that breed true to low THC levels well under 0.3% to insure a viable future for the hemp farm and our cannabis industry as a whole. The future of hemp is very bright, and I know this will be a key component in its destiny here in the United States.


A study was completed showing Cannabinoid (and terpene) increase at higher elevations. (

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