Cannabis Science

13 May 2021

What is a Cannabis Hermie?

Growers researching the growth habits and life cycle of cannabis in their cultivation journeys will undoubtedly come across the term “hermie”, or hermaphrodite, and the difficulties they can present to a crop. The term is used to describe cannabis plants whose flowers contain both male and female sexual organs. There is extensive discussion in the cannabis growing community about how hermies occur, but it is generally posited to be the combination of genetics and stress. 

Growers should be aware that their plants may develop hermaphrodite characteristics despite their best efforts, and the good news is that steps can be taken to mitigate its effects. Hermaphroditism is not a death sentence for a cannabis crop, however, and the grower who finds hermie flowers on their plants will still be able to harvest their flowers successfully if they are vigilant and take decisive action.

Why Herm Plants are Dangerous for Growers

Cannabis plants reproduce via male and female sex organs. Female cannabis plants require the pollen produced by male cannabis plants to create seeds. When female plants are pollinated, it causes their flowers to degrade in quality as the energy that is required to concentrate cannabinoids (such as THC and CBD) and terpenes to the desired highest levels possible are redirected instead to produce seeds.

Marijuana seeds produced by pollinated plants are usually a mixed selection of male and female plants, which introduces more difficulties for growers. After the seeds are germinated and grown out, growers will need to identify, isolate and destroy any male plants to avoid repeating the cycle of pollination. This creates extra work for growers, in addition to the resource drain of germinating and growing out male plants they will get rid of. This is the danger presented by hermaphrodite plants.

Unpollinated female flowers will continue to grow into large, dense, and resinous buds desired by growers and consumers. It is understood that the increase in size and density is directly related to the need for pollination. The flower with the largest surface area has the best chance of being pollinated even by a single, minuscule grain of male pollen.

The cannabis community has yet to understand precisely why marijuana plants develop hermaphroditic characteristics, and the best defence cannabis growers have is to be as vigilant as possible about their grow room conditions and to scout their plants as often as they can.

Consistent environmental conditions (no light leaks) in the growing setup will minimise the stress that can play a role in hermie-ing and regularly scouting plants will help growers catch any hermie plants as early as possible if these unwanted characteristics develop as a result of the plant’s genetics rather than environmental stress.

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Buds: Males, Females, Hermies

Once established following germination, cannabis plants will spend several weeks in the veg stage, developing their external structure and internal systems that will help produce flowers. As the plants are primarily developing leaves, stems, and roots, it is difficult for the grower to tell the sex of the plant at this stage. Generally, cannabis plants reveal their sex when they are between three and seven weeks old. After some time in veg, plants will have several levels of nodes – points on the plant where the leaves and branches meet the main stem – which is where flowers develop.

Male plants may show their preflowers when they are as young as three weeks old. Female plants generally take a little longer and start developing preflowers when they are between four and six weeks old. Eight weeks after germination is a good cut-off for the grower to determine the sex of their cannabis plants.

Male flower buds look like small, bulb-like clusters hanging from thin stems growing out of the node, with a curved protrusion at the bulb’s end that culminates in a blunt point. When the male flower ripens, the bulb opens, revealing five simple petals that range from yellow to cream in colour. Each has a stamen in the middle that releases pollen. Growers researching characteristics of male and hermie buds may find these pollen sacks referred to as “bananas” or “nanners.”

Female buds develop directly on the node itself, showing as teardrop-shaped pods (calyxes) from which protrude two pistils (wispy white hairs, also known as stigmas). The placement of the buds in relation to the node – dangling from stems in the case of males as opposed to growing directly on the node for females – is a good reference for the grower when determining the sex of their plants.

Hermaphrodite flowers will show primarily as females before growing male flowers in addition to female buds. A hermie’s male flowers may be interspersed amidst their female buds. Alternatively, they may appear in clusters (like grapes), or they may occupy one or more entirely separate branches. This unpredictability is part of the difficulty of managing hermied plants.

Female marijuana plants may develop male flowers due to stressful conditions, including heat stress and irregular light cycle during flowering, or drastic changes in the environment. Growers in northern California, for example, have experienced robust female plants developing hermaphroditic characteristics as a result of uneven light distribution due to smokey atmospheric conditions because of massive wildfires.

Cannabis plants with indica-leaning growth habits may respond to unnatural light cycles by developing photoperiod response disorders, such as female plants developing hermie characteristics when exposed to prolonged dark periods during early veg.

Some growers have characterised the late development of male flowers on female plants during flowering as an acute survival response: plants who have done all they can to grow large and dense to attract even a single molecule of pollen will grow male reproductive organs to ensure the pollination of their female flowers.

Cultivars of cannabis exist that contain hermaphrodite genes, and it’s sometimes possible that a grower will just have poor luck when it comes to their genetics. These may manifest late in the flowering stage, with female plants producing male flowers just as they ripen. In general, this is an indicator of ripeness and does not pose a danger to the garden since the plants are to be harvested shortly.

Hermaphrodite cannabis plant also known as a hermie

Observation Breeds Confidence and Informs Decisive Action

There are several ways of tackling the issue of hermie plants in a crop. The safest approach is to remove any plants with male flowers entirely from the garden (even if it’s a champion plant) because the risk to the rest of the buds in the garden is too great to leave a hermie plant to pollinate the rest of the crop. A good, if a tedious strategy is for the grower is to observe the plants as often as they can: any hermaphrodite cannabis plants that are identified as early as possible and removed will decrease the chance of pollinating the rest of the crop.

If the grower identifies a hermie plant in a batch of one strain in a crop of different cultivars, it’s a good idea to move the rest of that batch away from the rest of the crop. This will remove the risk of other plants in the strain developing hermie characteristics and pollinating the rest of the garden. The grower cultivating a single plant with hermie characteristics may have some success pinching off the hermie structures such as pollen sacs (or “nanners” ): be sure to moisten the male buds (and their own fingers) with water as this will prevent its pollen from dispersing to the air after they have been picked off.

The most critical phase of the cannabis plant life cycle is the transition between the veg and flowering phases. Any training activities that will stress the plant (and induce the development of hermie characteristics) such as pruning, staking, or low-stress training should be carried out during veg and pre-flower (when the plants stretch) before the development of buds. A balanced diet of nutrients, good hygiene, and proper watering will also help mitigate any kind of stress that could cause plants to hermie.

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Post author
Martin
Martin is a production horticulturist with experience in commercial cannabis cultivation and sustainable farming from his time with Emerald Cup Award-winning farmers Esensia Gardens in northern California's Emerald Triangle.
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