Hermaphroditism is when a plant develops both male and female reproductive organs. In cannabis, this occurs when female plants form pollen-producing structures in addition to buds. When that happens, the plant can pollinate itself and others nearby. Since the value of cannabis lies in the concentration of the cannabinoids produced by unpollinated female buds, hermaphroditism can ruin an entire crop.
Understanding hermaphroditism
Cannabis is dioecious; each plant is either male or female. Its sex is determined by genetics, epigenetics and phytohormonal regulation, although environmental conditions can influence how sex is genetically expressed.[1] Sexual dimorphism[2] appears in the early veg phase, and the primary way to distinguish male from female plants is by their flowers. However, some female plants may develop male reproductive organs alongside female ones, resulting in hermaphroditism.
Colloquially called “hermies,” these plants bear both female (pistillate) and male (staminate) flowers. They develop anthers in their leaf axils or within the buds, alongside their female flowers. The number of anthers can range from just a few to many.[3]
Why it’s a problem
Only genetically female plants are cultivated for cannabis production because their seedless flowers are rich in cannabinoids. Female plants develop trichomes—resin glands rich in cannabinoids like Δ⁹-THC, CBD and CBG—that are absent in male flowers.[4]
When female plants are pollinated, they redirect energy from trichome production to seed development, which significantly lowers cannabinoid concentration.[5]
Because this reduces both quality and value, seeded buds are typically rejected by recreational and medicinal markets. And since cannabis is anemophilous (wind-pollinated), if even small amounts of pollen become airborne in the grow room, they can compromise an entire crop.
Causes of hermaphroditism
While some cannabis strains are genetically predisposed to hermaphroditism due to unstable breeding or excessive inbreeding, any female plant can develop hermaphroditic traits under certain conditions, particularly environmental stress. Stress affects internal phytohormone levels, such as auxin:gibberellin ratios, which can trigger the formation of male flowers.[6]
Interrupting the dark cycle is a common cause, along with over- or underwatering, irrigating with cold water, pest infestations and poorly executed transplantation.[7] Research shows that low temperatures and shortened photoperiods increase male flower development in outdoor cultivation. One study also found that exposing female plants to extended darkness during early growth or changing the photoperiod during flowering can induce hermaphroditism.[8]
Exposure to certain chemicals, such as silver nitrate and cobalt chloride, can also cause hermaphroditism.[9]
Identifying and managing hermaphroditic plants
Early identification and removal of hermaphroditic plants is critical to protecting the grow room from unwanted pollination. To do this, growers must distinguish between male and female reproductive parts.
The main difference is the presence of pistils—little “hairs” that appear on female flowers but not on male ones. Female flowers are open, while male flowers form pollen sacs that look like small balls and can take up to three weeks to open.[10]
If a plant develops both male and female flowers, it’s a hermie (Figure 1).
Figure 1. A hermaphroditic cannabis plant presenting male and female flowers. Image source: 10.51584/IJRIAS.2023.8709. Malabadi, Ravindra B., Kiran P. Kolkar, Raju K. Chalannavar, Antonia Neidile Ribeiro Munhoz, Gholamreza Abdi, and Himansu Baijnath. 2023. “Cannabis sativa: Dioecious into Monoecious Plants Influencing Sex Determination.” International Journal of Research and Innovation in Applied Science 8 (7): 2454-6194. https://doi.org/10.51584/IJRIAS.2023.8709.
Identifying and managing hermaphroditic plants
Early identification and removal of hermaphroditic plants is critical to protecting the grow room from unwanted pollination. To do this, growers must distinguish between male and female reproductive parts.
The main difference is the presence of pistils—little “hairs” that appear on female flowers but not on male ones. Female flowers are open, while male flowers form pollen sacs that look like small balls and can take up to three weeks to open.[10]
If a plant develops both male and female flowers, it’s a hermie (Figure 1).
Image Source
Figure 1. A hermaphroditic cannabis plant presenting male and female flowers. Image source: 10.51584/IJRIAS.2023.8709. Malabadi, Ravindra B., Kiran P. Kolkar, Raju K. Chalannavar, Antonia Neidile Ribeiro Munhoz, Gholamreza Abdi, and Himansu Baijnath. 2023. “Cannabis sativa: Dioecious into Monoecious Plants Influencing Sex Determination.” International Journal of Research and Innovation in Applied Science 8 (7): 2454-6194. https://doi.org/10.51584/IJRIAS.2023.8709.
Inspecting during flowering
Male flowers can develop in just hours, so growers must inspect their plants daily. Use a magnifier to check each plant thoroughly from top to bottom, focusing on the nodes where branches meet the main stalk; these are common sites where flowers emerge. Male flowers may be hidden beneath nodes or embedded within dense female buds (Figure 2).
One study found that a handheld Raman spectrometer equipped with an 831-nanometer laser could distinguish male, female and hermaphroditic plants based on carotenoid levels.[11] This tool may be useful for large-scale operations where manual inspection of every plant is impractical.
Inspecting during flowering
Male flowers can develop in just hours, so growers must inspect their plants daily. Use a magnifier to check each plant thoroughly from top to bottom, focusing on the nodes where branches meet the main stalk; these are common sites where flowers emerge. Male flowers may be hidden beneath nodes or embedded within dense female buds (Figure 2).
Image Source
Figure 2. The progression of male anthers developing in female flowers of the cannabis strain “Moby Dyck.” Image source: Punja, Zamir K., and Janesse E. Holmes. 2020. “Hermaphroditism in Marijuana (Cannabis sativa L.) Inflorescences – Impact on Floral Morphology, Seed Formation, Progeny Sex Rations, and Genetic Variation.” Frontiers in Plant Science 11: 718. https://doi.org/10.3389/fpls.2020.00718.
One study found that a handheld Raman spectrometer equipped with an 831-nanometer laser could distinguish male, female and hermaphroditic plants based on carotenoid levels.[11] This tool may be useful for large-scale operations where manual inspection of every plant is impractical.
Removing hermies and relocating plants of the same strain
Any identified hermies should be removed and destroyed immediately to prevent them from pollinating the rest of the crop. Plants of the same strain should also be isolated as a precaution, as they may be genetically predisposed to hermaphroditism. Keep these plants in a separate room or grow tent with limited airflow so that, if they develop into hermies, there’s no risk of pollinating the rest of the grow room.
Preventing hermaphroditism
The most effective way to prevent hermaphroditism is to grow high-quality, genetically stable strains and minimize stress, especially during flowering. Maintain optimal conditions, including temperature, humidity, irrigation and nutrients. Practice good hygiene and monitor plants closely for signs of pests or disease.
Since light exposure during dark cycles can trigger hermaphroditism, check for light leaks in the grow room. Cover any light sources (such as indicator lights), and ensure light timers are functioning accurately.
Complete all pruning and plant training early, ideally during the veg phase or initial flowering stretch, before buds begin to form.
Hermaphroditism is a serious risk to cannabis operations, threatening both the quality and value of the crop. By sourcing stable genetics, maintaining a healthy environment and monitoring regularly, growers can reduce the chance of this natural phenomenon compromising their product.
Emerald Harvest Team
[1] Petit, Jordi, Elma M. J. Salentijn, Maria-Joao Paulo, Christel Denneboom, and Luisa M. Trindade. 2020. “Genetic Architecture of Flowering Time and Sex Determination in Hemp (Cannabis sativa L.): A Genome-Wide Association Study.” Frontiers in Plant Science 11: 569958. https://doi.org/10.3389/fpls.2020.569958.
[2] Condition where sexes of the same species exhibit different morphological characteristics such as in color, shape, size and structure.
[3] Punja, Zamir K., and Janesse E. Holmes. 2020. “Hermaphroditism in Marijuana (Cannabis sativa L.) Inflorescences – Impact on Floral Morphology, Seed Formation, Progeny Sex Rations, and Genetic Variation.” Frontiers in Plant Science 11: 718. https://doi.org/10.3389/fpls.2020.00718.
[4] Goff, Nicolas K., James F. Guenther, John K. Roberts III, et. al. 2022. “Non-Invasive and Confirmatory Differentiation of Hermaphrodite from Both Male and Female Cannabis Plants Using a Hand-Held Raman Spectrometer.” Molecules 27 (15): 4978. https://doi.org/10.3390/molecules27154978.
[5] Lipson Feder, Carni, Oded Cohen, Anna Shapira, et. al. 2021. “Fertilization Following Pollination Predominantly Decreases Phytocannabinoids Accumulation and Alters the Accumulation of Terpenoids in Cannabis Inflorescences.” Frontiers in Plant Science 12: 753847. https://doi.org/10.3389/fpls.2021.753847.
[6] Punja, Zamir K., and Janesse E. Holmes. 2020. “Hermaphroditism in Marijuana (Cannabis sativa L.) Inflorescences – Impact on Floral Morphology, Seed Formation, Progeny Sex Rations, and Genetic Variation.” Frontiers in Plant Science 11: 718. https://doi.org/10.3389/fpls.2020.00718.
[7] Malabadi, Ravindra B., Kiran P. Kolkar, Raju K. Chalannavar, Antonia Neidile Ribeiro Munhoz, Gholamreza Abdi, and Himansu Baijnath. 2023. “Cannabis sativa: Dioecious into Monoecious Plants Influencing Sex Determination.” International Journal of Research and Innovation in Applied Science 8 (7): 2454-6194. https://doi.org/10.51584/IJRIAS.2023.8709.
[8] Punja, Zamir K., and Janesse E. Holmes. 2020. “Hermaphroditism in Marijuana (Cannabis sativa L.) Inflorescences – Impact on Floral Morphology, Seed Formation, Progeny Sex Rations, and Genetic Variation.” Frontiers in Plant Science 11: 718. https://doi.org/10.3389/fpls.2020.00718.
[9] Ibid.
[10] Malabadi, Ravindra B., Kiran P. Kolkar, Raju K. Chalannavar, Antonia Neidile Ribeiro Munhoz, Gholamreza Abdi, and Himansu Baijnath. 2023. “Cannabis sativa: Dioecious into Monoecious Plants Influencing Sex Determination.” International Journal of Research and Innovation in Applied Science 8 (7): 2454-6194. https://doi.org/10.51584/IJRIAS.2023.8709.
[11] Goff, Nicolas K., James F. Guenther, John K. Roberts III, et. al. 2022. “Non-Invasive and Confirmatory Differentiation of Hermaphrodite from Both Male and Female Cannabis Plants Using a Hand-Held Raman Spectrometer.” Molecules 27 (15): 4978. https://doi.org/10.3390/molecules27154978.
