There is a bit of confusion as to what constitutes industrial hemp and what constitutes cannabis. Is it the same plant? Is it different? Opinions vary from the highest levels of government on down to the common citizen. Plainly and simply put: they are not the same thing. They are closely related, but industrial hemp is not marijuana and marijuana is not industrial hemp. If you come away with nothing else here, remember that.
Both plants are members of the same species, Cannabis sativa, but they are not the same thing. Many people, including some in academia, believe hemp is nothing more than just male cannabis plants. However, this is not true. They are genetically different. The primary difference between them is that hemp and marijuana have dramatically different levels of the psychoactive chemical delta-9-tetrahydrocannabinol (THC). In hemp, THC levels are generally less than one percent. Legally, hemp is generally required to be less than 0.3 percent THC as these levels are not thought to have any psychoactive effects. Marijuana plants, on the other hand, range in their respective levels of THC. On average, they have between three and twenty percent, though many cultivated species have levels of more than thirty percent.
Besides having different levels of THC, hemp and marijuana are grown differently for different market purposes. Some of the differences between the two are also semantical. “Marijuana” generally refers to the flowering tops and leaves of cannabis varieties that deliver some amount of body or head high to the user. “Hemp” often refers to the leaves, stalks, fibers, or seeds of the hemp plant grown for their industrial or commercial use.
Botanically, most biologists consider hemp and marijuana to be varieties of the same species (Cannabis sativa). So, how can two plants that are almost genetically identical be so different in function and form? Think of the differences in dogs. All dogs are classified as Canis familiaris, but we have all seen the great variation in their sizes, colors, and temperaments. Though they are closely related and genetically similar enough to cross breed, nobody is going to confuse a Great Dane with a Chihuahua. Industrial hemp and marijuana are no different; they are of the same genus and species but have different characteristics.
Hemp leaves tend to be skinnier than marijuana’s wider leaves. Hemp also tends to be a taller and skinner plant, while marijuana grows fuller, fatter, and shorter. Not to add even more confusion, but there are similar physical differences between the different marijuana types of sativa, indica, and ruderalis. As noted above, the primary difference between marijuana and hemp is in their chemical compositions. Hemp, having little to no THC, tends to have high levels of cannabidiol (CBD). The level of CBD, of course, is not the main defining factor as sativa, indica, and ruderalis marijuana strains can have varying degrees of CBD in tandem with varying degrees of THC.
There is a wide gap between the cultivation methodologies for hemp and weed. Hemp crops can tolerate a wide range of temperatures and are grown in many parts of the world, whereas marijuana plants are usually restricted to warmer climates. The typical growing season for hemp crops is between 100 and 120 days. Marijuana’s range is generally more like 60-90 days.
Industrial hemp plants are grown as close together as four inches, often in large plots, with up to 50 plants per square foot. This dense planting reduces branching and flowering, meaning industrial hemp plants are typically grown as a single main stalk with a few leaves and branches. Hemp growers that wish to realize high yields grow their plants tall. They can be towering, with some species reaching heights of up to 15 feet. Hemp is grown primarily for its two types of fiber, bast and hurd. Bast is the outer portion of the hemp stem and hurd is the pith or interior fiber.
When cannabis is grown for marijuana, it is almost always done with the intent to produce and harvest the female flowers (and often the leaves). The female flowers are short, clustered, and full of THC. So, unlike hemp cultivation, marijuana is cultivated to encourage the plant to become bushy with wide branches and heavily foliated to promote flowers and buds. This requires that plants be well-spaced, generally six to 10 feet apart, with no more than two plants per square yard. That’s more than 200 times more space than a single hemp plant is afforded.
It should be noted that growers that produce both hemp and marijuana (or produce one crop near a grower who produces the other) do so at their own risk. Cannabis plants are open-, wind-, and insect-pollinated, and hemp and marijuana are related closely enough to cross breed (again, think of dog species). Cross-pollination between the two crops would spell disaster for the quality and intent of either. It could reduce the desired psychoactive effects of marijuana or render a hemp crop illegal due to increased THC levels. Even the cross-pollination of a hemp crop with inferior hemp plants (or a marijuana crop with inferior weed plants) is not desirable. Some fiber and seed crops are valued based on their purity and any dilution of that could make a crop less marketable.
All these differences do not cover the full spectrum of variations between industrial hemp and marijuana, of which there are thousands. This does not even consider the scores of differences in legal opinion, laws, ordinances, and other governance pertaining to the differences between the two crops, regardless of the intended use and if based in science or popular opinion. The bottom line is: they are very closely related, but are not the same plant.