Although “cannabis” and “hemp” are technically the same species of plant, in the botanical world, there are essentially two kinds of cannabis plants – industrial plants and medicinal plants.

We can think of “hemp” as the industrial plant and “cannabis” as the medicinal plant. Industrial plants include plants grown for fiber and seed oil. Medicinal plants include intoxicating THC-rich plants and non-intoxicating CBD-rich plants.

The main difference between hemp plants and cannabis plants is resin content. Industrial hemp plants are low-resin plants. Medicinal plants are high-resin plants. “Marijuana” (spelled with a ‘j’ or ‘h’) is the colloquial name for the flower tops of high resin cannabis.

Industrial hemp varieties are typically grown from pedigree seed, yielding as many as one hundred tall, skinny, bamboo-like plants (with skimpy foliage) per square meter. These plants are machine harvested and manufactured into many different products like paper, cloth, and edible oil.

Medicinal plants, by comparison, are typically grown from asexually reproduced clones, one to two bushy plants per square meter, and the flowers are hand-harvested, dried, trimmed and cured. The flowers are then consumed for their intoxicating and medicinal effects.

History of U.S. Cannabis Prohibition

U.S. federal law originally defined “marihuana” in terms of resin content. Resin was mentioned no less than three times in the two-sentence definition of “marihuana” encoded in the 1970 Controlled Substances Act (CSA), which was copied word-for-word from the 1937 Marihuana Tax Act, the legislation that made cannabis effectively illegal:

The term “marihuana” means all parts of the plant Cannabis sativa L. [sic], whether growing or not; the seeds thereof; the resin extracted from any part of such plant; and every compound, manufacture, salt, derivative, mixture, or preparation of such plant, its seeds or resin. Such term does not include the mature stalks of such plant, fiber produced from such stalks, oil or cake made from the seeds of such plant, any other compound, manufacture, salt, derivative, mixture, or preparation of such mature stalks (except the resin extracted therefrom), fiber, oil or cake, or the sterilized seed of such plant which is incapable of germination.

1937 Marihuana Tax Act

In essence, the CSA asserts that certain parts of the plant (“mature stalk” and “sterilized seed”) are exempt from the legal definition of marijuana. But the flowers, the leaves, and the sticky resin were not included in this exemption. The resin and its derivatives were explicitly forbidden wherever they are found on the plant.

The CSA was unequivocal on this point: the resin from any part of the cannabis plant, or any preparation made from the resin, is illegal.

Fiber produced from hemp stalk and oil pressed from unfertilized hempseed got a pass, but not the resin. But as far as medicinal and recreational cannabis goes, the resin is where the action is.

It’s all about the resin

Cannabis resin is contained within the heads of tiny, mushroom-shaped trichomes, found mainly on the plant’s female flowers (the buds) and to a lesser extent on the leaves. The sticky, gooey resin contains THC (tetrahydrocannabinol) and CBD (cannabidiol), along with hundreds of other secondary plant metabolites (primarily other cannabinoids and terpenes) that augment human brain chemistry and ease physiological and psychological distress.

Hemp seed oil, it should be noted, is not the same as CBD-rich oil extracted from the flowers and leaves of the plant. 

Oil pressed from hemp seed contains no CBD, no THC, no plant cannabinoids to speak of, but it’s excellent for making varnish, paint, soap, protein-enriched food supplements, and much more.

A tiny amount of THC makes it “cannabis”

Right from the start, the Feds understood that resin content is the key factor that distinguishes marijuana from industrial hemp.

Today, however, federal law includes a recently added caveat that officially characterizes industrial hemp as having no more than 0.3 percent THC by dry weight. Products containing such a tiny amount of THC should not have an intoxicating  effect.

Where did the 0.3 percent THC figure come from? 

It stems from a 1976 taxonomic report by Canadian plant scientists Ernest Small and Arthur Cronquist., who never intended for 0.3 percent THC to function as a legal demarcation between hemp and other forms of cannabis.

But that’s exactly what happened.

According to current federal law, cannabis is considered hemp – not marijuana – as long as no part of the plant (including the leaves and flowers) exceeds a THC concentration of “more than 0.3 percent on a dry weight basis.” Any plant that tops 0.3 percent THC is considered marijuana and is therefore federally illegal to grow, according to Uncle Sam.

The passage of the Agricultural Act of 2014 (otherwise known as the Farm Bill) defined “industrial hemp” for the first time in U.S. history and distinguished it legally from marijuana.

The “0.3 percent THC or less” qualification for hemp was enshrined in Section 7606 of the Agricultural Act and renewed when Congress approved the 2018 Farm Bill.

There was no mention of resin in the 2018 Farm Bill, which a cynic might refer to as the “Keep Marijuana Illegal Bill.”

To put it bluntly, the 0.3 percent THC legal limit is an arbitrary, impractical, euphoria-phobic relic of reefer madness. Although it lacks a scientific basis, it has become the latest lynchpin of cannabis prohibition, a dishonest policy that impedes medical discovery and blocks patient access to valuable therapeutic options, including herbal extracts with various combinations of CBD and THC.

CBD’s Increased Availability

Despite its shortcomings, the Farm Bill is a momentous leap forward. It is now legal for American farmers to cultivate hemp as a commercial crop on domestic soil – a long overdue development catalyzed by the huge public demand for CBD.

On the day it became law (December 20, 2018), the Farm Bill removed hemp, but not cannabis, from the list of controlled substances.

The Farm Bill also explicitly removed hemp products, including hemp-derived CBD, from the purview of CSA – but not from the purview of the Food and Drug Administration (FDA), which maintains that hemp-derived CBD is neither a legitimate food supplement nor a medication approved for off-label use.

Meanwhile, CBD oil derived from any cannabis plant with over 0.3 percent THC remains a Schedule 1 substance under federal law.

It’s unclear how regulators will tell the difference between illegal cannabis-derived CBD oil and seemingly not-illegal, hemp-derived CBD oil given that the actual CBD molecule is the same.

Identifying the best CBD products

The best source of CBD oil is organically grown, high-resin, CBD-rich cannabis not low-resin industrial hemp. Why? Because the more resin in the plant, the more CBD there is to extract.

Low-resin industrial hemp grown for fiber or seed oil is not an optimal source of CBD for several reasons:

  • Industrial hemp typically contains far less cannabidiol than high-resin CBD-rich cannabis, so a large amount of industrial hemp is required to extract a small amount of CBD. This raises the risk of contaminants as hemp is a “bio-accumulator”— meaning the plant naturally draws toxins from the soil. That’s wonderful for phyto-remedial purposes, but it’s not so great for making ingestible medicinal oil products. Oil extracted from hemp and cannabis will concentrate the toxins as well as the good stuff
  • CBD oil is often a co-product or byproduct of industrial hemp grown primarily for another purpose. Farmers can make additional money if they sell their unused hemp biomass to a business that wants to extract CBD from the leftovers. This dual-use practice is widespread and barely regulated, if at all, and the hemp biomass is often tainted with residues of pesticides and toxic solvents that are used to extract the CBD.
  • Heavily refined CBD paste or CBD-isolate derived from industrial hemp is poor starter material requiring dilution for formulating CBD-rich oil products.
  • Compared to high-resin cannabis, low-resin hemp is more vulnerable to pest and mold infestation because the resin contains terpenes as well as cannabinoids that repel predators, attract beneficial insects, and protect plants from blight.
  • Industrial hemp is less chemically diverse than high resin cannabis, lacking the robust mix of medicinal terpenes and secondary cannabinoids commonly found in high resin cannabis. These compounds interact with CBD and THC to enhance their therapeutic benefits.

Beyond Cannabis vs Hemp

Prior to the 2018 Farm Bill, most of the CBD products available in the United States were derived from low-resin industrial hemp grown in Europe and China. Now that cultivating hemp is legal again in the United States, it should be easier to obtain better quality CBD products made from hemp grown in Colorado, Kentucky, Oregon, Montana, Vermont and other states.

The most prodigious source of cannabidiol are high-resin CBD-rich cannabis plants that tip the scales at 20 percent CBD by dry weight and around one percent THC.

Unfortunately, under the current legal regime that’s too much THC to qualify as hemp, even though anyone who smoked the resinous flower tops wouldn’t get high because CBD is not intoxicating like THC. It can, however, do a person a world of good if they are struggling with pain or anxiety or depression.

Cannabis is a highly adaptable botanical; it can thrive in various environments, legal and ecological. It responds well to the human hand, which has stretched the genetic capabilities of the plant in unprecedented ways.

Growing hemp for CBD extraction

Cultivating hemp for CBD extraction is an artifact of marijuana prohibition. The distinction between low resin industrial hemp and high resin psychoactive cannabis (“marijuana”) has always been problematic with respect to CBD.

According to a genomics study by the University of Minnesota and Sunrise Genetics (a hemp breeding company), most high CBD hemp – or “hemp wink wink,” as we like to say at Project CBD – actually gets 90 percent of its genetics from high resin marijuana, not low resin hemp.

In the botanical world, what makes one plant marijuana and another hemp has more to do with the richness of resin content than the amount of allowable THC, as arbitrarily defined by prohibitionist lawmakers.


Against a shifting regulatory landscape, the distinction between hemp and other forms of cannabis is fast becoming moot.

American horticulturists are successfully breeding high-resin cannabis varietals that satisfy the Farm Bill’s criteria for hemp – with THC measuring below 0.3 percent and double-digit CBD levels by dry weight.

In other words, farmers are now growing high resin cannabis (“marijuana”) with less than 0.3 percent THC. If that sounds a bit confusing, that’s because it is a bit confusing.

But this much is clear: if grown, extracted and processed well, these CBD-rich plants qualify as good starter material for manufacturing CBD oil for medicinal and personal use.

Martin A. Lee is the director of Project CBD. He’s authored and edited several books, including Smoke SignalsAcid Dreams, and The Essential Guide to CBD. © Copyright, Project CBD. May not be reprinted without permission.