What Other Plants Produce THC Besides Cannabis?

No plant besides cannabis produces Δ9-tetrahydrocannabinol (THC) in any pharmacologically meaningful amount. The enzyme responsible for making THC’s immediate precursor, THCA synthase, has so far been found only in Cannabis sativa. However, a handful of other plants make molecules that look strikingly like THC under a microscope or that interact with the same receptors THC targets in the human body. The distinction matters: structural resemblance and receptor activity are not the same thing as “contains THC,” yet the plants involved are genuinely interesting and worth understanding on their own terms.

Why THC Production Is Essentially Unique to Cannabis

THC does not exist in the plant itself in its active form. Cannabis produces THCA (tetrahydrocannabinolic acid), which converts to THC when heated. The final step in making THCA is performed by THCA synthase, an enzyme that takes a precursor called CBGA (cannabigerolic acid) and folds it into THCA through a specific chemical reaction.¹ This enzyme was first identified in 1995, and the gene encoding it was subsequently cloned and characterized.²

No other plant has been found to carry the THCA synthase gene naturally. Some plants share earlier steps in the pathway, producing CBGA or related precursors, but without that final enzymatic step, they cannot convert those precursors into THCA or THC. This is the biochemical bottleneck that keeps THC production confined to cannabis in the natural world.

The Liverwort That Comes Closest

If any plant deserves the title of “nature’s other THC source,” it is a small, unremarkable liverwort in the genus Radula. Radula marginata, found in New Zealand and Tasmania, produces a compound called perrottetinene (PET) that is structurally analogous to THC.³ When researchers first examined PET’s three-dimensional shape, they noticed it mirrors THC closely enough to fit into the same receptor, the CB1 receptor in the brain, that THC activates to produce its psychoactive effects.⁴

PET and THC are not identical molecules. PET belongs to a chemical class called bibenzyls, while THC is a terpenophenolic compound. They arrived at similar shapes through entirely different biosynthetic routes in organisms separated by hundreds of millions of years of evolution. Computational modeling has shown that PET and THC share a binding mode inside the CB1 receptor, which helps explain why PET can produce some cannabinoid-like effects in animal studies.⁵

There is an important caveat, though. The concentration of PET in Radula tissue is quite low. The levels found naturally in the plant are not enough to produce the kind of high that THC delivers in cannabis. Preparations made from Radula are sold online as a legal alternative, and the liverwort has a history of use as a herbal medicine among Māori people, but the pharmacological punch is modest compared to a cannabis product. Researchers are more interested in PET as a lead compound for drug development than as a recreational substitute. Because PET may retain some of THC’s anti-inflammatory and pain-reducing properties at doses too low to be strongly psychoactive, it represents a potential pathway toward medicines that harness cannabinoid receptor activity without producing an intense high.

Helichrysum and the Case of Convergent Evolution

Helichrysum umbraculigerum, a South African plant in the daisy family sometimes called the woolly umbrella, has drawn attention because it produces cannabigerolic acid (CBGA) at concentrations reaching about 4.3% of dry weight.⁶ CBGA is the same precursor molecule that cannabis uses to make THC, CBD, and other cannabinoids. But Helichrysum does not take the next step. Without THCA synthase or CBDA synthase, it cannot convert CBGA into THC or CBD. The compound just accumulates in its precursor form.

What makes Helichrysum scientifically remarkable is not that it produces THC (it doesn’t) but that it evolved the ability to make CBGA completely independently from cannabis. The two plants are not closely related at all. Cannabis belongs to the family Cannabaceae, while Helichrysum is an Asteraceae, in the same family as sunflowers and daisies. Genetic analysis has confirmed that cannabinoid synthesis evolved in parallel in these two lineages, meaning the two plants independently arrived at similar chemistry without sharing the relevant genes through a common ancestor.⁶ This kind of convergent evolution suggests that producing cannabinoid-like molecules confers some survival advantage significant enough for natural selection to stumble upon it more than once.

Rhododendron’s Cannabinoid-Like Compounds

Researchers studying Rhododendron anthopogonoides, a species used in traditional Chinese medicine, have isolated compounds that share structural features with several cannabis cannabinoids. Two novel compounds, named anthopogocyclolic acid and anthopogochromenic acid, were identified alongside five others that resemble cannabichromene (CBC), cannabicyclol (CBL), and cannabicitran (CBT).⁷ Geranyl orsellinic acid, a known early intermediate in cannabinoid biosynthesis, was also found in the plant.

None of these compounds is THC, and none has been shown to activate CB1 receptors the way THC does. Their significance lies more in what they reveal about plant chemistry: the molecular building blocks that cannabis uses to make its famous cannabinoids are not exclusive to cannabis. Rhododendron, Helichrysum, and Radula all represent independent evolutionary experiments with overlapping chemistry, supporting the broader idea that cannabinoid-type molecules are a recurring theme in plant biochemistry.⁸

Plants That Activate Cannabinoid Receptors Without Making Cannabinoids

Beyond plants that make cannabinoid-shaped molecules, a separate group of plants produces compounds that interact with the human endocannabinoid system through entirely different chemistry. These are sometimes called cannabimimetics, meaning they mimic the effects of cannabinoids at the receptor level even though they are structurally unrelated to THC.

Black Pepper, Cloves, and Beta-Caryophyllene

Beta-caryophyllene (BCP) is a terpene found in the essential oils of black pepper, cloves, rosemary, hops, oregano, cinnamon, and many other common spice and food plants. It is also present in cannabis itself as a major component of the essential oil. In 2008, researchers demonstrated that BCP selectively binds to the CB2 cannabinoid receptor with meaningful affinity and acts as a functional agonist, leading to it being called “the first dietary cannabinoid.”⁹

CB2 receptors are found mainly on immune cells and in peripheral tissues rather than in the brain, so activating them does not produce a high. Instead, CB2 activation is associated with anti-inflammatory effects. In animal studies, BCP has shown pain-relieving properties in models of both inflammatory and nerve-related pain, and those effects were blocked when the CB2 receptor was knocked out, confirming the mechanism.¹⁰ BCP has also attracted interest for its potential anti-inflammatory activity through CB2 and other receptor pathways.¹¹

The practical takeaway is that you are almost certainly eating dietary cannabinoids already. Every time you grind black pepper onto a meal or cook with oregano, you consume small amounts of BCP. Whether those dietary amounts are large enough to produce noticeable effects through CB2 activation is still an open question, but the receptor binding is real and well documented.

Echinacea and Its Alkylamides

Echinacea is best known as an herbal supplement marketed for immune support. The active compounds responsible for much of Echinacea’s biological activity are alkylamides, and research has shown that at least two of these bind to the CB2 receptor more strongly than the body’s own endocannabinoids do.¹² These alkylamides show strong selectivity for CB2 over CB1, meaning they influence immune function without crossing into psychoactive territory. Further work on Echinacea root extracts has confirmed that multiple alkylamides act as CB2 agonists.¹³

This finding reframes the traditional use of Echinacea in an interesting way. For decades, people have taken Echinacea tinctures and teas believing they help with colds and inflammation. The CB2 receptor connection offers one plausible mechanism for why some users report feeling a difference, even if clinical trials on cold prevention have been mixed. The alkylamides are structurally nothing like THC, but they end up at the same biological doorstep.

Kava and Yangonin

Kava (Piper methysticum) is a Pacific Island plant whose roots are traditionally prepared as a calming, mildly sedating drink. Among the kavalactones responsible for kava’s effects, one called yangonin stands out because it binds to the CB1 receptor, the same receptor THC activates in the brain.¹⁴ Yangonin is selective for CB1 over CB2, which is the opposite pattern from BCP and Echinacea’s alkylamides. In animal studies, yangonin injected directly into the spinal canal produced pain-relieving effects that were completely reversed when a CB1-blocking drug was co-administered, confirming that the pain relief runs through the cannabinoid receptor.¹⁵

Yangonin’s affinity for CB1 is weaker than THC’s, and it is just one of several kavalactones working together in the plant. The relaxing effects of a bowl of kava likely result from multiple mechanisms acting in concert, with CB1 binding being one contributor rather than the whole story. Still, kava is the only widely consumed plant beverage outside cannabis where a direct CB1 receptor interaction has been demonstrated for one of its active compounds.

Why Plants Bother Making These Compounds

A natural question is why unrelated plants would independently evolve molecules that happen to interact with animal cannabinoid receptors. The answer, at least in cannabis, appears to be pest defense. A study testing cannabinoid-free, CBD-dominant, and CBG-dominant cannabis genotypes found that cannabinoid-free plants suffered significantly more damage from chewing insects. Caterpillars fed on leaves with higher cannabinoid concentrations ate less, grew less, and survived at lower rates.¹⁶ The cannabinoids appear to function as chemical armor against herbivores.

Whether the cannabinoid-like compounds in Helichrysum, Rhododendron, or Radula serve the same defensive role in those plants has not been tested as rigorously. But the convergent evolution pattern is suggestive. When natural selection independently arrives at similar chemistry in distantly related lineages, it usually means the chemistry solves a shared problem. Deterring insects and microbial pathogens is about as universal a problem as plants face.

Fungi and Microbes That Boost Cannabis Cannabinoid Production

While no microbe has been shown to produce THC on its own in nature, certain fungi that live in or around cannabis roots can significantly increase the plant’s cannabinoid output. Inoculation of hemp with arbuscular mycorrhizal fungi and endophytic fungi boosted both CBD and THC concentrations in leaves and shoots compared with uninoculated control plants.¹⁷ The strongest effects came from specific fungal species, and interestingly, plants inoculated with endophytic fungi had higher cannabinoid concentrations than those given mycorrhizal fungi, though the mechanisms differ between the two groups.

This finding is relevant for hemp and cannabis cultivation. Growers looking to increase cannabinoid yields without heavy synthetic fertilizer inputs may find fungal inoculants useful. The fungi don’t make the cannabinoids themselves; rather, they improve the plant’s nutrient uptake and seem to stimulate the plant’s own cannabinoid production pathways. It is a partnership, not an independent source of THC.

Yeast That Has Been Engineered to Produce THC Precursors

If no other plant naturally makes THC, scientists have asked whether they can put the necessary genes into a simpler organism and let it do the work. The answer is yes, at least at laboratory scale. Researchers have engineered baker’s yeast (Saccharomyces cerevisiae) to produce THCA, CBDA, and CBCA from simple sugar and hexanoic acid by inserting the relevant cannabis biosynthetic genes into the yeast genome.¹⁸ Separate work has pushed this further, engineering yeast to produce rare cannabinoids like THCP (tetrahydrocannabiphorol), a compound that occurs in cannabis only in trace amounts and is difficult to extract in useful quantities.¹⁹

The yields are still small. One group reported CBGA titers of about 18 milligrams per liter in a fed-batch yeast fermentation, and olivetolic acid (an earlier precursor) at roughly 117 milligrams per liter.¹⁸ These are proof-of-concept numbers, not industrial production levels. But the trajectory is clear: the synthetic biology community views yeast-based cannabinoid production as a viable future alternative to agricultural cultivation, particularly for rare cannabinoids that are impractical to harvest from plants.²⁰

An intriguing finding from the yeast work is that the product spectrum of the transplanted cannabinoid synthases depended heavily on the pH of the growth medium. By adjusting pH, researchers could shift which cannabinoid the yeast preferentially produced. That kind of tunability does not exist in a cannabis field, and it hints at why fermentation-based production may eventually complement or even replace plant-based extraction for specific cannabinoid molecules.

Why the “Other Plants Make THC” Claim Persists

Online articles frequently claim that plants like Echinacea, black pepper, chocolate, or kava “produce cannabinoids” or even “contain THC.” The confusion stems from conflating three very different things: producing actual THC, producing a molecule that shares structural features with THC, and producing a molecule that happens to bind a cannabinoid receptor. Only cannabis does the first. A few plants like Radula and Rhododendron do the second. And a wider range of plants, including common spices, do the third.

The endocannabinoid system is not a cannabis-specific system that other plants occasionally tap into. It is an ancient signaling network present in nearly all animals, and its receptors respond to a variety of molecular shapes. Your body makes its own cannabinoids (anandamide and 2-AG) that have no structural relationship to THC whatsoever. So it should not be surprising that other plant molecules can also fit into these receptors without being THC or even resembling it. The fact that Echinacea’s alkylamides bind CB2, or that black pepper’s BCP does the same, tells us more about how flexible these receptors are than about any secret kinship between those plants and cannabis.

For anyone hoping to find a legal, non-cannabis plant that delivers the same experience as THC, the honest answer is that nothing in the botanical world replicates it. Radula’s PET is the closest structural analog, but its natural concentrations are too low to produce a comparable effect. BCP and Echinacea’s alkylamides target the immune-focused CB2 receptor, not the brain-focused CB1 receptor that drives THC’s psychoactive effects. Yangonin from kava does hit CB1, but weakly and as part of a broader pharmacological profile that feels nothing like cannabis. The uniqueness of cannabis, in the end, comes down to that one enzyme, THCA synthase, and no other plant has evolved it.