What is THCa Flower?

THCa flower refers to cannabis buds marketed as hemp. These buds are intended for smoking or vaping. They contain high concentrations of tetrahydrocannabinolic acid (THCa) and low concentrations of D9. Specifically, their D9 levels do not exceed 0.3% by dry weight. For example, I recently viewed a certificate of analysis (COA) of THCa flower that showed 25% THCa and 0.18% D9. This is remarkable for a few reasons. Despite that this flower is federally lawful hemp, smoking it will get you very high. In fact, this “total THC” profile is very much in line with cannabis flower sold in regulated marijuana markets. This is because the advertised “THC” values for flower in regulated marijuana markets is almost always “total THC”, meaning the sum of D9 plus 87.7% of the THCa. This is technically written as: THCa(%wt.)× 0.877+∆9THC(%wt.) (Note that this well-used formula may be flawed, at least with respect to finished products, an issue that does not impact the analysis in this article but which may ultimately impact the industry at large.)

Recently, I reviewed a COA for a sample of Durban Poison, one of the most popular marijuana strains. It is typically advertised as having THC concentrations between 15%-25%.  The THC concentrations in the Durban Poison COA I viewed were 20.67%, right in line with what would be expected for this strain. Of that total amount of THC, the D9 level was only 1.24%. The rest of the THC was in the form of THCa, which registered at 22.15%. This profile is typical for marijuana flower. “THC” that is advertised in marijuana almost always refers to total THC, of which THCa is usually found in the highest concentrations. Although THCa does not have an intoxicating effect when ingested, the reason this total THC profile is acceptable to marijuana smokers is that THCa converts to D9 when heated in a chemical process called decarboxylation. Smoking or vaping creates sufficient heat to convert some of the THCa to D9.

In summary, THCa hemp flower is no different from marijuana flower currently sold in medical and recreational marijuana dispensaries in states with regulated marijuana markets.

Is THCa Flower legal?

The short answer is, “Yes”, at least under federal law and the laws of some states. But do not stop reading here! CONTINUE READING for important caveats and legal risks!

The idea that there are legal hemp buds that are no different from illegal marijuana buds seems counterintuitive, but proving that this is true involves a very straightforward analysis. The 2018 Farm Bill distinguishes legal hemp from illegal marijuana solely by reference to its D9 levels. Specifically, hemp is cannabis with no more than 0.3% D9 by dry weight. So, a hemp bud with THCa levels of 20% and D9 levels of 0.15% falls squarely within the 2018 Farm Bill’s definition of “hemp” and is legal under federal law.

In fact, the DEA specifically agrees that cannabis material meeting this definition is lawful. In a letter written to my colleague and friend, Shane Pennington, on January 6, 2022, the DEA states: “material that is derived or extracted from the cannabis plant such as tissue culture and any other genetic material that has a delta-9 tetrahydrocannabinol concentration of no more than 0.3 percent on a dry weight basis meets the legal definition of “hemp” and is thus not controlled under the CSA.” This is not the first time the DEA has confirmed that the sole factor distinguishing lawful hemp from unlawful marijuana is its D9 concentration. In addition to confirming this standard in both a letter to the Alabama Board of Pharmacy and a public statement to the Florida Department of Agriculture and Consumer Services (both of which can be viewed by clicking here), the DEA’s Interim Final Rule regarding hemp states that marijuana is limited “to only include cannabis or cannabis-derived material that contain more than 0.3% delta-9-tetrahydrocannabinol (also known as D9 -THC) on a dry weight basis.”

In summary, harvested cannabis flower with D9 concentrations not exceeding 0.3% meets the legal definition of “hemp” and is not controlled under federal law, regardless of its THCa levels.

What About Total THC?

The obvious response to the above analysis is, “What about the USDA requirement that hemp must pass a test prior to it being harvested to ensure that its total THC concentrations do not exceed 0.3%?” In its Laboratory Testing Guidelines issued on January 15, 2021, the USDA requires a “total THC” test for pre-harvest hemp: “Tests shall measure the total THC concentration in a sample submitted to a laboratory for analysis. The laboratory will perform chemical analysis on the sample using postdecarboxylation or other similarly reliable methods where the total THC concentration level considers the potential to convert delta-9-tetrahydrocannabinolic acid (THCA) into THC.” Additionally, in its Final Rule regarding hemp production, the USDA mandates that a pre-harvest hemp compliance test take into account the “potential” THC in a sample by requiring the test to take account of the “total THC, derived from the sum of the THC and THCA content, shall be determined and reported on a dry weight basis.” Based on the USDA’s requirement for total THC testing, it seems that hemp flower with high THCa levels should not be lawful, right?

The answer is, “Not necessarily”. The USDA rule only applies to hemp production, which means hemp cultivation. The USDA does not regulate hemp once it has been harvested and its testing regulations do not apply to hemp that has been harvested. Provided that a pre-harvest hemp sample passes the “total THC” test, it is lawful hemp, regardless of the THCa concentrations present in the harvested material. Interestingly, the DEA and the USDA seem to be at odds about this issue. As discussed above, the DEA does not seem to care if the cannabis material was grown by a licensed hemp grower or whether it even passed a pre-harvest test. In stark contrast to the USDA, the DEA solely relies on the D9 concentrations of cannabis materials in determining their legal status, regardless of whether they passed a USDA pre-harvest test, or even if they were tested at all before harvesting.

In any event, and regardless of this inter-agency dispute, the fact remains that harvested hemp is not subject to the total THC standard under federal law. The only metric that matters is the concentration of D9. I have discussed this issue at length, including the various ways in which a hemp bud from a compliant hemp crop can have total THC levels in excess of 0.3%, in an article you can read by clicking here.

What Are the Major Legal Issues with THCa Flower?

Although THCa hemp flower is lawful under federal law, there are some important issues and considerations to be aware of. The rest of this article will discuss these issues.

Is it possible to grow compliant THCa flower?

One issue is whether THCa flower, at least with the high THCa concentrations discussed at the beginning of this article, can come from hemp grown in compliance with the USDA total THC requirements. Compliant THCa flower may be theoretically possible, but this does not mean it actually exists in the real world. Consider a physics example: although absolute zero can technically exist, it has yet to be attained in a laboratory setting. THCa flower may be like absolute zero – lawful in theory but unattainable in the real world due to the testing limitations described above. I am fortunate to represent some of the best cannabis growers and geneticists in the world. I asked some of them about this issue. Most seem to think it is unlikely that a plant with THCa concentrations in the 20% zone will pass a pre-harvest USDA total THC test, regardless of the genetics or the testing methods used, though they do not rule out the possibility. At least one of them offered that perhaps compliant hemp flower could be sprayed with THCa extract.

It is important to reiterate that the DEA considers all cannabis material with D9 levels not exceeding 0.3% by dry weight to be lawful “hemp”, regardless of whether or not it was grown by a licensed hemp producer and/or if it passed a USDA total THC pre-harvest test. As I mentioned above, this disagreement between the USDA and the DEA is an unsettled area of law.

What About State Laws?

Another issue is whether THCa flower is lawful under state law. The answer depends on the state in question. It is absolutely clear that you can lawfully transport THCa flower through a state, regardless of its hemp laws. This is because the 2018 Farm Bill states: “[N]o State or Indian Tribe shall prohibit the transportation or shipment of hemp or hemp products produced in accordance with subtitle G of the Agricultural Marketing Act of 1946 (as added by section 10113) through the State or the territory of the Indian Tribe, as applicable.” But individual states may restrict or even downright prohibit it. THCa flower is completely lawful in some states, such as North Carolina, which does not contain a “total THC” standard for hemp in any of its statutes or regulations. On the other hand, THCa flower is restricted in some states, such as Oregon, which use a “total THC” standard for post-harvest hemp. The legal status of THCa flower in some states can be tricky to determine due to the way that their hemp laws and regulations are written. For instance, under Pennsylvania’s hemp plan a permitted hemp processor may only receive or use cannabis material that passes a total THC test. However, this rule only applies to permit holders. Since retailers of finished hemp products are not required to have a hemp permit, the total THC requirement does not appear to apply to them.

In summary, the laws and regulations of a given state determine the extent to which THCa flower is lawful. This can sometimes be difficult to determine, which leads to the final issue: confusion and misunderstanding of hemp laws.

What if THCa is Lawful in My State but Law Enforcement Disagrees?

A final issue to consider is confusion by law enforcement and state regulators about the legal status of THCa flower. Many people in the hemp industry, including some hemp lawyers, contend that hemp flower is only lawful if it passes a “total THC” test. As discussed above, this is wrong under federal law and the laws of some states. Given that this issue is confusing even to experienced hemp lawyers, you can imagine its misunderstanding is compounded by law enforcement and even regulators, many of whom do not know or care much about (or for) hemp. In practice, this means that someone lawfully selling THCa flower may experience problems, including prosecution, from law enforcement. When seized and tested using gas chromatography (GC), the standard for most state crime labs, THCa flower will show very high D9 levels. This is because GC heats up the sample sufficiently to decarboxylate the THCa and convert it to D9. When this occurs, it is possible that the retailer will be charged with trafficking marijuana. Aside from experiencing the stress and expense of being charged with a crime, it is also possible that the prosecution and the judge will not understand the subtleties of the law, and the retailer will be found guilty, regardless of the fact that THCa is lawful in the jurisdiction. I believe in the justice system and do not want to imply that a criminal prosecution will always go wrong in this scenario; however, it is important to understand that this is a novel and complicated legal issue and there is no guarantee that things will go the right way in a criminal trial.


THCa flower is poised to be the “next big thing” in Hempland. As discussed above, THCa flower is lawful under federal law and the laws of some states. However, before deciding to participate in the emerging THCa flower market it is very important to understand the issues and risks involved.

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