There’s a lot of misinformation and confusion surrounding hemp vs marijuana, which has led to both terms being used interchangeably. While they both derive from the Cannabaceae family, each plant serves an entirely different purpose.
Marijuana is primarily used for medical and recreational applications and has high levels of THC (the psychoactive cannabinoid that gets you “high”). Hemp (also known as industrial hemp) has extremely low levels of THC (less than 0.3%) and is primarily used to create a variety of products such as textiles, ropes, fabrics, foods, and beverages.
Although, before we dive into the key differences, it’s important to understand why they are similar and where a lot of the confusion lies.
Cannabis refers to a genus of plants within the Cannabaceae family. The Cannabis genus has three distinct species (or subspecies depending on what you read) including Cannabis sativa, Cannabis indica, and Cannabis ruderalis. These three species/subspecies once had distinct physical appearances that were suggestive of their chemical profile and thus effects (e.gTHC-dominant or CBD-dominant). However, due to the extensive inter-breeding and hybridization of cannabis, these physical distinctions now provide little indication of each cannabis strain’s chemotype. 
Nevertheless, it is generally accepted that marijuana is grown from either of these three species, while hemp is only grown from the Cannabis sativa, which actually means “cultivated cannabis”.  This distinction is exceptionally important as new laws within most US states classify Cannabis sativa L. and subspecies as the only legal cultivars allowed.
Cannabis sativa L. species (discovered by Linnaeus 1753)
Cannabis indica Lam. subspecies (discovered by Lamarck 1783)
Cannabis ruderalis Janisch. subspecies (discovered by Janisch 1975)
So, what exactly are the key differences between hemp and marijuana?
Key Differences Between Hemp vs Marijuana
1. Physical Appearance
Due to its industrial purposes, hemp plants are cultivated to look distinctly different from marijuana plants. Typically tall and skinny with very few flowering buds, industrial hemp plants are grown to utilize both the stalks or seeds (or a hybrid of both). They have few branches, skinnier leaves, and look almost like a wild weed.
Marijuana plants, on the other hand, are short and bushy with broader leaves, making them stand out when placed next to hemp plants. If you saw both plants side by side, you would assume they were a separate species, just like many of our early botanists!
2. Tetrahydrocannabinol (THC) Content
Although, the biggest differentiating factor between hemp and marijuana is each plant’s tetrahydrocannabinol (THC) content. Tetrahydrocannabinol (THC) is responsible for the psychological effects of cannabis. In addition to several other effects, THC stimulates brain cells to release dopamine, resulting in marijuana's well-known “high.” Marijuana is specifically bred to contain high levels of THC for both recreational and medicinal purposes, typically around 5-35% (depending on the strain). This is the crucial reason marijuana is classified as an illegal Schedule I drug in the United States under federal law.
Hemp, on the other hand, has a substantially lower THC concentration of less than 0.3% per dry weight and produces much higher levels of cannabinoid (CBD) than marijuana. Research has shown that CBD actually counteracts the psychotropic effects of THC, and its chemical profile effectively means it’s impossible to experience any intoxicating side-effects with hemp. 
Hemp is selectively bred for consumer and industrial purposes. Heavily regulated by federal law, hemp can’t contain a concentration of more than 0.3% THC, as it would then be considered marijuana and, therefore, illegal.
3. Cultivation of the Plant
Hemp and marijuana are grown and harvested in completely different ways due to their application. Marijuana plants can be both male or female, or even hermaphrodite; although, female plants are preferred as they produce buds essential for achieving maximum levels of THC.
Marijuana typically has a 60-90 day growth cycle and needs to be planted with ample space between each to cultivate properly (approximately 6 feet apart). It needs to grow in a carefully controlled environment with lots of attention to maintain appropriate light, temperature, humidity, oxygen levels, and much more.
A lot less care is needed for hemp. It can be grown outdoors and close together (up to 4 inches apart) in large fields designed to maximize yield. Most cultivated hemp varieties are dioecious (separate male and female plants), with different plant parts harvested for different purposes (fiber, seed, flowers, leaves). However, some there are also monoecious varieties (male and female flowers on the same plant).  Hemp is also much more versatile, similar to a weed, and can flourish in a variety of climates, with a growth cycle of approximately 108-120 days.
4. Legal Status
There’s been a lot of controversy over the legality of cannabis, particularly regarding the presence of THC. Hemp was listed as a Schedule I drug under the Controlled Substances Act of 1970 and made illegal in the United States. While this brought on the decline of the hemp industry, it also increased misconceptions about the plant and its association with marijuana and getting “high.”
However, President Trump recently signed the Farm Bill (Agriculture Improvement Act of 2018), legalizing industrial hemp throughout the country and making it, once again, a normal agricultural commodity (you still need permits to grow hemp commercially). 
The lines are a little more blurry when it comes to marijuana. Because of the high THC content, marijuana is still illegal under federal law (Schedule I substance). And to make it even more confusing, the rules vary significantly state-by-state. For example, there are now 10 states (plus Washington DC), which have legalized recreational marijuana (users over 21 years of age), and 33 states (including DC) which have legalized medical marijuana.
Deciphering the Difference Between Hemp and Marijuana
Hopefully this article has helped clarify the distinction. Hemp doesn’t contain any THC and is used to create a wide variety of products (clothing, textiles, food and dietary, CBD oil,etc.). Marijuana is carefully cultivated to achieve higher levels of THC for both medicinal and recreational purposes.
While they share some similarities and both come from the same family, hemp and marijuana are distinctively different in their physical appearance, chemical makeup, and cultivation.