Industrial hemp and marijuana are both plants of the species Cannabis sativa. Cannabis sativa has multiple uses, from fiber production to food production to medicinal and psychoactive uses. Delta-9 tetrahydrocannabinol (Δ-9-THC) is the primary psychoactive compound in cannabis and is responsible for the mood-altering “high.” Within Cannabis sativa there are several varieties, each grown for a different primary use. In genetics there are always trade-offs. For a variety to specialize in one trait, it must sacrifice gains in other traits. A very long time ago, farmers who wanted to use Cannabis sativa for fiber production selected seed from plants that grew very tall with a large fiber content. Within a plant’s nutrient budget, growing tall and producing flowers with a high THC content are both very expensive. For a cannabis plant to grow taller than normal, it has to take nutrients away from THC production. Thus, plants that were selected for high performance in fiber operations over time grew bigger while also producing less and less THC. It is these varieties that industrial hemp comes from.
Industrial hemp varieties differ from THC varieties because, over thousands of years, farmers bred these varieties to excel at increasing biomass for fiber production, producing more seeds for seed production, or increasing oil production for culinary purposes. Since the plants only have so much energy to work with, they divert energy away from THC production and instead use it to perform the function the farmers bred them to perform.
While a history of selective breeding and natural mutation got us to the present day with a large number of varieties of Cannabis sativa, the modern definition of industrial hemp in the United States is a legal one. By law, industrial hemp is defined as the plant Cannabis sativa L. that has a total Δ-9-THC concentration that does not exceed 0.3% on a dry-weight basis (FDACS 2020). If a Cannabis sativa plant’s THC concentration becomes greater than 0.3%, it exceeds the legal limit for industrial hemp, and then may be defined as marijuana, an illegal Schedule 1 drug. By contrast, the average THC content of recreational marijuana in 2018 was 16.16% (DEA, 2019). For this reason, the State of Florida tightly monitors farmers who grow industrial hemp and require that samples of the crop be tested before harvest to ensure that THC levels remain below the 0.3% THC threshold.
FDACS. 2020. “Florida Administrative Code Rule 5B-57.014 – State Hemp Program.” Accessed on May 13, 2021. https://www.fdacs.gov/content/download/91558/file/rule-5b-57.014.pdf
DEA. 2019. 2019 Drug Enforcement Administration National Drug Threat Assessment. https://www.dea.gov/sites/default/files/2020-02/DIR-007-20%202019%20National%20Drug%20Threat%20Assessment%20-%20low%20res210.pdf