The short answer to whether plants appreciate being exposed to cannabis smoke is no. The idea that plants thrive in the presence of this smoke misunderstands plant biology and the composition of combustion byproducts. The immediate effects are detrimental, introducing harmful substances directly onto the plant’s surface and into its atmosphere. This analysis breaks down the components of the smoke and how these substances interact with plant physiology.
What is in the Smoke and How Does it Affect Plants?
Cannabis smoke is a complex mixture containing hundreds of compounds generated by combustion. These include airborne particulate matter, commonly known as tar or ash, and toxic gases like carbon monoxide and nitrogen oxides. Exposure to the heat generated by the burning material also causes localized thermal stress to delicate plant tissues.
The most visible physical harm comes from fine particulate matter settling as a sticky film on the leaves. Plants breathe through microscopic pores called stomata, which are concentrated mostly on the underside of leaves. When smoke particles coat the leaf surface, they physically block these pores. This blockage inhibits the plant’s ability to regulate gas exchange and transpire water vapor, slowing down photosynthesis and causing physiological stress.
Carbon monoxide, a byproduct of incomplete combustion, is present in smoke and can directly interfere with plant respiration. These airborne toxins and physical blockages trigger a defensive response in the plant. The plant may voluntarily close its stomata to prevent the absorption of perceived pollutants, which further reduces carbon dioxide uptake and slows growth.
Addressing the CO2 Benefit Misconception
A common belief is that exhaled smoke provides a boost of carbon dioxide (CO2) that enhances photosynthesis. While CO2 is a raw material for photosynthesis, the concentration and delivery method from smoke are negligible compared to the harm. Ambient air contains approximately 400 parts per million (ppm) of CO2.
To see a measurable benefit from CO2 enrichment, commercial growers maintain levels between 800 and 1200 ppm in a sealed environment. The small, transient puff of CO2 from exhaled smoke quickly dissipates into the surrounding air. This provides no sustained increase in concentration and is immediately outweighed by the simultaneous delivery of heat, tar, and carbon monoxide.
Furthermore, the CO2 delivered is accompanied by the physical blockage of stomata by smoke residue. If the pores are clogged, the plant cannot efficiently take in carbon dioxide, regardless of its concentration. The overall negative impact of the particulate matter and toxins far exceeds any theoretical benefit from the minimal CO2 contribution.
Absorption of Cannabinoids by Plants
A specific question involves whether non-cannabis plants can absorb active compounds like delta-9-tetrahydrocannabinol (THC) or cannabidiol (CBD) from the smoke. Cannabinoids are large, complex organic molecules that are highly lipophilic, meaning they dissolve in fats and oils. The smoke delivers these compounds as microscopic droplets of resin and tar that passively deposit onto the plant’s foliage.
For a plant to absorb and distribute a compound systemically, the substance must first penetrate the waxy outer layer, known as the cuticle. This cuticle acts as a biological barrier, designed to prevent water loss and block the entry of pathogens and large molecules. While small mineral ions and certain small organic molecules can be absorbed through the cuticle or stomata, the large size and complex nature of cannabinoids make this penetration highly inefficient.
Consequently, while smoke residue containing THC and CBD settles on the leaf surface, the plant does not actively absorb or translocate these compounds into its vascular system in any meaningful way. The cannabinoids remain as surface contaminants. A plant exposed to smoke will simply be a dirtier, stressed plant, not one that has incorporated the compounds into its tissue structure.