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What’s the difference between hemp and marijuana? By legal definition in the U.S., it really boils down to THC content. The distinction being whether the cannabis crop has more or less than 0.3% THC by dry weight. In most of Europe, the limit is even lower at 0.2%. But where did these legal limits even come from?

Blame Canada. Or, at least, blame Canadian Scientist Dr. Ernest Small, who is credited with being the originator of the 0.3% figure. 

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Let’s Talk Total THC

We’ve heard the allowable 0.3% THC figure, but what exactly does this mean? 

“Total THC” in the cannabis plant refers to the amount of both THCA (raw THC, which converts into THC when heated) and THC present. So when we’re talking about total THC content, we’re including both THCA and THC when calculating the percentage in the crop. 

To further clarify the definition, “by dry weight,” simply means that the percentage of THC present is calculated in relation to the total plant weight when harvested and dried. 

So, now that we’re savvy about the THC, let’s talk about that 0.3%.

The Magic Number

It is widely recognized that this 0.3% THC cutoff for hemp is fairly arbitrary. Like Cinderella’s carriage turning back into a pumpkin at the stroke of midnight, hemp magically turns into “marijuana” by classification once it exceeds this limit. 

The 0.3% dry weight figure originated from a scientific research paper entitled Small, E., and Cronquist, A. 1976. A practical and natural taxonomy for Cannabis. Taxon 25: 405-435.

In that paper, Cannabis sativa was defined with “Δ9-THC comprising less than 0.3% (dry weight) of upper, younger leaves, and usually less than half of cannabinoids of resin,” and Cannabis indica as “with Δ9-THC comprising more than  0.3% (dry weight) of upper, younger leaves, and frequently more than half of cannabinoids of resin.” 

While the definition found in this paper did also make mention of Cannabis sativa having limited intoxicant ability with Cannabis indica having a higher propensity to produce intoxicating effects, this division between sativa and indica cannabis varieties was not intended to be a prescriptive measure of the plant’s capacity to get users high. Read: this distinction between hemp and marijuana based on THC limit is not necessarily a factor that can indicate whether a strain will or will not get users high. 

Dr. Small explains further on the Cornell University FAQ page. Straight from the horse’s mouth:

“Over the years, I have had many inquiries regarding whether the 0.3% criterion was based on potential for abuse – i.e. the possibility of using hemp to get high.

“No, it was not – the criterion was based on the pattern of variation in the real world: it happens that for thousands of years people have selected plants for fiber (subsp. sativa; low-intoxicant plants) and for marijuana (subsp. indica; high-intoxicant plants), and my studies simply revealed this pattern.”

Despite this, as well as the fact that most cannabis material must contain at least 1% THC to even approach producing psychoactive effects, the Canadian government moved forward using Small’s distinction as the basis for legislation. And, following Canada’s lead, the U.S. moved forward following this same guideline when it started changing regulations around cannabis.

Hemp Going Forward

Dr. Small did also note the challenges the current legal landscape provides for the CBD industry, particularly as hemp with up to 1% THC still offers a world of possible benefits if it is permitted to be produced. Specifically, with regards to CBD production, this 0.3% THC cut-off is particularly limiting as there are few strains that produce high levels of CBD without also producing an amount of THC that exceeds the legal limit. 

Because of this, many hemp and CBD companies are hoping to push for an alteration to this limit going forward - but, as long as the U.S.’s limit is higher than European nations and we can remain competitive, that may be a difficult needle to shift. 

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