What Is Hemp?

Hemp is Cannabis sativa L. with no more than 0.3% delta-9-tetrahydrocannabinol (delta-9-THC) by dry weight at harvest. It has been federally legal in the United States since the 2018 Farm Bill removed it from the Controlled Substances Act. Hemp is the legal source of every hemp-derived cannabinoid sold in the U.S. market, including CBD, delta-8, and the high-THCA flower that dominates the smokable hemp category.

“Hemp” sounds like a different plant from “marijuana,” and walking the aisle of any health food store you would be forgiven for thinking it is. The hemp seeds in your granola bowl, the rope in your hardware aisle, and the high-potency THCA flower sold online are all the exact same species — Cannabis sativa L. The only thing distinguishing them is one number written into one paragraph of one law. This article explains that number, why it matters, and what hemp actually contains.

The legal definition (2018 Farm Bill)

Hemp’s modern legal identity in the United States dates to December 20, 2018, when President Trump signed the Agriculture Improvement Act of 2018 — better known as the 2018 Farm Bill, Public Law 115-334. Section 10113 of that act amended the Agricultural Marketing Act of 1946 to define hemp this way:

The term “hemp” means the plant Cannabis sativa L. and any part of that plant, including the seeds thereof and all derivatives, extracts, cannabinoids, isomers, acids, salts, and salts of isomers, whether growing or not, with a delta-9 tetrahydrocannabinol concentration of not more than 0.3 percent on a dry weight basis.

Three load-bearing pieces of that definition matter for everything that follows:

• The 0.3% threshold is on delta-9-THC specifically — not “total THC,” not THCA, not cannabinoids in aggregate. Delta-9.
• The measurement is on a dry weight basis — i.e. after the plant has been dried and trimmed for testing.
• “All derivatives, extracts, cannabinoids, isomers, acids, salts, and salts of isomers” — meaning the legal carve-out extends beyond the raw plant to anything made from compliant hemp, which is the legal foundation for hemp-derived CBD, delta-8, THCP, and THCA flower.

The same act removed hemp from Schedule I of the Controlled Substances Act, where it had sat since the Marihuana Tax Act framework migrated into the CSA in 1970. The USDA was tasked with implementing a federal hemp production framework, which it did in 7 CFR Part 990, the USDA Hemp Production Program rule. Every legal hemp grower in the United States operates under either that federal rule or a USDA-approved state plan with equivalent terms.

Hemp vs marijuana: same plant, different threshold

Botanically, “hemp” and “marijuana” are not different species. Genetic sequencing work — including the often-cited Sawler et al. (2015) PLOS ONE study on the structure of Cannabis genetic variation — finds that drug-type and fiber/grain-type cannabis are differentiated populations within a single species, not separate species. The older taxonomic argument over sativa vs indica vs ruderalis is essentially historical at this point; modern taxonomy treats them all as Cannabis sativa L., following Small & Cronquist (1976).

What separates hemp from marijuana legally — and only legally — is that 0.3% delta-9-THC line.

Notice what is not in the legal definition: there is no THCA limit, no total-cannabinoid limit, and no requirement that the plant be incapable of producing intoxication. A hemp plant testing 25% THCA and 0.25% delta-9-THC at harvest is, by federal law, hemp. Once that flower is dried, packaged, and lit, it converts THCA to delta-9-THC and produces a recognizably standard cannabis high. This is not a loophole that exists by accident — it is the direct, predictable consequence of measuring delta-9 at harvest rather than total potential THC after decarboxylation.

Industrial hemp categories

The 2018 Farm Bill does not subdivide “hemp” by intended use, but the industry does. Four broad categories cover the meaningful crops grown today.

Fiber

Long-stalk varieties grown for the bast fiber (long, strong fibers used in textiles, paper, rope, insulation, and biocomposites) and the hurd (the woody inner core, used in hempcrete and animal bedding). Fiber hemp is grown densely, harvested before flowering, and produces no commercially relevant cannabinoids.

Grain

Hemp seed varieties grown for human food (hemp hearts, hemp protein, hemp seed oil) and animal feed. Hemp seed is rich in essential fatty acids (alpha-linolenic acid in particular) and complete protein. The seeds themselves contain effectively no cannabinoids — cannabinoids accumulate in the resin glands of the flower, not the seed.

CBD and cannabinoid

Varieties bred for high cannabinoid content in the female flower. The same agronomy supports CBD-dominant cultivars, CBG-dominant varieties, and high-THCA cultivars. This is the modern dominant value-creating category — the difference between selling fiber at $0.05/lb and selling smokable flower at $200/lb. Almost every product sold on a hemp directory like ours falls into this category. See our THCA flower buying guide for the dominant subcategory.

Floriculture / smokable hemp

Subcategory of the above: cannabinoid-rich flower harvested, dried, cured, and trimmed for smoking rather than extraction. Smokable hemp is what most consumers experience as “hemp flower.” High-THCA cultivars — Donny Burger, White Runtz, Candy Gas, and dozens of others — are the standard products.

The THCA category, plain language

The THCA category exists because of the harvest-time delta-9 measurement required by federal law and most state laws.

Living cannabis plants produce essentially zero delta-9-THC. They produce THCA — the carboxylated, non-psychoactive precursor. Delta-9-THC only appears as the plant ages, dries, and is exposed to heat or UV light, which slowly decarboxylates the THCA into THC. At the moment of harvest — when the federal compliance test is taken — a high-THCA hemp plant can show 25% THCA and 0.25% delta-9, comfortably under the 0.3% line.

Once that plant is dried, cured, packaged, and ignited at 350 °C in a joint or a vape coil, the THCA decarboxylates into delta-9-THC. The user inhales delta-9-THC at full strength. Pharmacologically, the experience is indistinguishable from cannabis purchased at a state-licensed marijuana dispensary.

This is not a regulatory mistake — it is a structural feature of how the 2018 Farm Bill defined hemp. For the chemistry side of the same story, see our primer on what THCA is and the contrast in THCA vs THC. We track active congressional efforts to close the carve-out (notably the Mary Miller amendment and Senate “total THC” proposals) in the federal hemp bill tracker.

Hemp’s legal status state by state

Federal legalization in 2018 did not preempt state law. States retain authority to regulate hemp and hemp-derived products within their borders, and dozens of states have enacted hemp rules diverging from the federal baseline.

Three patterns dominate:

• States that follow the federal “delta-9 only” rule. Texas (HB 1325), North Carolina, and roughly 20 others measure compliance against delta-9 alone and treat high-THCA hemp flower as a legal product.
• States with a “total THC” definition. Florida, California, Tennessee, Oregon, and a growing number of others have either passed or pending legislation that adds THCA × 0.877 to delta-9 in the compliance calculation, effectively banning high-THCA flower.
• States that ban smokable hemp outright. Idaho, Hawaii, Utah, and a handful of others restrict or ban the smokable-flower category specifically, regardless of the cannabinoid math.

We maintain a 50-state directory updated as legislation moves. Always check before ordering.

International status

Hemp legality outside the United States is patchier. A short tour of the major markets:

• Canada. Industrial hemp is legal under the Cannabis Act (S.C. 2018, c. 16), but the Canadian framework does not have a “hemp-derived cannabinoid flower” category equivalent to the U.S. THCA carve-out. Cannabis flower of any potency is sold through the licensed cannabis market, not through hemp.
• European Union. The EU permits industrial hemp cultivation. The THC threshold rose from 0.2% to 0.3% effective 2023 under Common Agricultural Policy revisions. Member states regulate finished product sale individually, with most treating any noticeably psychoactive flower as a controlled substance regardless of source.
• United Kingdom. Hemp cultivation requires a Home Office license. Finished products containing more than 1 mg total THC per container are not lawfully sold to consumers, which effectively excludes high-THCA flower.
• Germany. Following the 2024 ban on HHC and the broader 2024 partial cannabis legalization, hemp-derived novel cannabinoids occupy uncertain ground. THCA-specific rules have not been fully codified as of this writing.

These categories shift frequently. If you are sourcing internationally, work with a customs broker and confirm current rules with the destination country’s regulator.

What’s actually in a hemp plant

Beyond the legal framework, it is worth knowing what the plant itself produces.

• Cannabinoids. Currently 100+ identified, dominated by CBDA in CBD cultivars, THCA in modern hemp drug cultivars, and CBGA as the upstream “mother cannabinoid.” Trace cannabinoids include CBN, CBC, CBDV, and the much-discussed THCP.
• Terpenes. The aromatic compounds responsible for the smell and much of the felt character of a strain. Caryophyllene, myrcene, limonene, linalool, pinene, terpinolene, and humulene dominate the cannabis terpene panel.
• Flavonoids. Cannflavin A and B and other polyphenols. Trace contributors to the experience.
• Bast fiber and hurd. Structural plant material that drives the industrial hemp side of the business — paper, textiles, hempcrete, biocomposites.

Cultivation 101

A short walk-through of how modern hemp is grown.

• Indoor versus outdoor. High-THCA cannabinoid hemp is overwhelmingly grown indoors or in light-deprivation greenhouses to maximize trichome production and to control the harvest window for compliance testing. Outdoor hemp tends to push higher THCA later in flower, which raises compliance risk.
• Pheno hunting. Breeders run hundreds or thousands of seedlings, identify the rare phenotypes that maximize THCA accumulation while keeping delta-9 under 0.3%, and clone those mothers for production runs.
• Compliant testing windows. USDA rules require sampling within 30 days before harvest, with retesting required if the original lot fails. A grower whose plants drift over 0.3% at the testing window may have to remediate (extract usable cannabinoids) or destroy the crop.

Common myths

A few persistent misunderstandings worth correcting.

• “Hemp can’t get you high.” False. High-THCA hemp flower, smoked, will produce the same effects as regulated-market cannabis. The legal status of the raw plant has nothing to do with the pharmacology of the smoke.
• “Hemp is just rope.” Outdated by at least a decade. The dominant economic value in modern hemp comes from cannabinoids, not fiber.
• “Hemp is a different plant from marijuana.” False. Same species. The distinction is regulatory — defined entirely by harvest-time delta-9 measurement.
• “All hemp is non-psychoactive.” Partly true (raw hemp is non-psychoactive) and partly misleading (heated high-THCA hemp absolutely is psychoactive).

Related reading

• What is THCA? — the cannabinoid most hemp flower is sold for
• THCA vs THC — the chemistry of the precursor
• Federal hemp bill tracker — what could change in the next Farm Bill
• 50-state hemp legality — state-by-state status
• How to read a Certificate of Analysis — verifying compliant hemp
• What is delta-8? — another major hemp-derived cannabinoid
• THCP vs THCA — the rarest hemp-derived cannabinoid
• THCA flower buying guide
• Verified hemp brands

Last reviewed 2026-04-28 by THCAmap Editorial. Not legal or medical advice. Adults 21+. Hemp law changes frequently; verify your state’s current status before purchasing or shipping.