You will sometimes hear the words “hemp”,  “marijuana” and “cannabis” used interchangeably, although each term is very specific.  While hemp and marijuana are regularly referred to as species or strains of Cannabis, this is not correct.  “Hemp” and “marijuana” are simply broad terms our culture has adopted mainly for legal purposes, however they are not legitimate nomenclature for the plant.

Hemp Definition:

In the United States, when we say “hemp” or “industrial hemp”, we are referring usually to specific cultivars of the Cannabis sativa plant that have a THC (the psychoactive component Tetrahydracannabinol) content of .3% or less.  These cultivars are used primarily in the production of cannabinoids like CBD (if the plants are allowed to flower unfertilized) and in the case of fertilized plants, they are used for hemp seed and fiber production.

Marijuana Definition:

When we are referring to “marijuana”, we are referring to Cannabis sativa or indica cultivars that are relatively high in THC (legally above .3%) and are grown primarily for their recreational psychoactive properties or their medicinal properties.

How to Tell them Apart:

There are no discernable external differences between a “marijuana” plant and a “hemp” plant.  From a botanist’s perspective, they could look identical.  Lab tests would have to be performed to determine what the THC content of each plant is in order to classify it as either “hemp” or “marijuana”.  The .3% limit for THC for industrial hemp in the US appears to be a random low percentage first proposed by scientists in a book published in 1979 as a way to differentiate the plants into useful categories.  However, the authors of the book later insisted that their original .3% limit on THC is arbitrary and should be changed. 

So, basically the difference between “hemp” and “marijuana” comes down to different cultivars, kind of like how we distinguish types of tomatoes.  Some tomato plants are cultivars that produce cherry tomatoes, some are cultivars that produce beefsteak tomatoes.  They’re all tomatoes, but they serve different purposes.  Same goes for hemp and marijuana – both are of the Cannabis genus of plants, but hemp plants are grown for industrial uses and cannabinoid production, while marijuana plants are grown for psychoactive benefits.