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What To Do With Hermaphrodite Cannabis Plants

As every grower knows, cannabis is a dioecious species, meaning it produces some plants that are exclusively female and others that are exclusively male. However, because mother nature loves to break her own rules, some cannabis plants actually contain both male and female sexy bits, and are therefore known as hermaphrodites. While this is fairly rare, most growers will come across hermaphroditism in their crop from time to time, so it’s important to know how to handle these plants.

Identifying hermaphrodites

As we explained in a previous post, it’s generally pretty easy to identify the sex of a cannabis plant, as females are adorned with pistillate flowers while males are hung with stamens that are often referred to as “bananas” because of their appearance.

Hermaphrodites are female plants that also contain one or more banana. These stamens can sometimes form inside the female flower itself, replacing the pistil, but will more often appear alongside the female inflorescences, occupying some of the plant’s nodes (where the branches meet the main stem).

A recent study found signs of hermaphroditism in five to ten percent of plants that were being grown indoors under commercial conditions[i]. While the frequency at which this occurs varies between strains, it’s clearly important to keep monitoring your plants throughout the flowering phase in order to spot any unwanted hermaphrodite inflorescences before they get a chance to self-pollinate.

The development of male stamens on a female flower, from emergence (a) to full maturity (f) over a period of three weeks. Image: Holmes et al. (2020)/Fronties in Plant Science

What’s the problem with hermaphroditism?

When growing cannabis it’s essential to prevent the females from being pollinated, which means your growing area needs to be a banana-free zone. This is because all of the cannabinoids are contained within the female flowers, which will grow to their maximum size if they don’t get fertilised. However, once pollinated, these plants will divert most of their energy to the production of seeds instead of resin, resulting in low-quality weed that is full of seeds but distinctly lacking in cannabinoids and terpenes.

To avoid any unwanted hanky-panky within the growing area, it’s become common practice to remove (and often destroy) the males, leaving the females to reach their full flowering potential. Yet this arrangement can be scuppered by an undetected hermaphrodite, which can easily fertilise an entire crop if it isn’t dealt with before its anthers open and release their pollen. So if you have meticulously eradicated all of your males but still end up with weed that is full of seeds, you know that one of your females must have developed into a hermaphrodite.

The production of pollen by a hermaphrodite inflorescence, from the development of anthers (a) to the release of pollen (d). Image: Holmes et al (2020)/Frontiers in Plant Science

How to prevent hermaphroditism?

While hermaphrodites may be a real nuisance, it’s worth remembering that all life on Earth has evolved with one purpose: to survive. In keeping with this universal drive to endure, cannabis hermaphroditism has developed as an adaptation to help the plant reproduce quickly when it feels threatened.

As such, it is always more likely to occur when the plant is under stress and thinks it needs to go to seed. This stress can be caused by any number of environmental factors, such as the overuse of pesticides and fertilisers, interruptions to the photoperiod, pruning during the flowering phase, too much or too little water, undesirable temperature or the presence of pests.

Eliminating this stress by providing the optimal growing conditions is therefore the best way to reduce the frequency of hermaphroditism in your crop. To do this, you’ll need to diligently monitor and control all of the above factors, while also making sure to harvest your flowers at the right time. If flowers become too mature without being fertilised then the plant may take matters into its own hands and start sprouting bananas so that it can self-pollinate. Knowing when to harvest can be an art in itself, and is typically determined by the colour of the trichomes, which turn from clear to milky to amber as they develop.

It’s also important to bear in mind that some strains will simply be more genetically prone to hermaphroditism than others, so it’s worth doing some research on this before buying seeds.

What to do with hermaphrodite plants

Given that the priority is to prevent pollination from occurring, you’ll always want to get rid of any male flowers. If a hermaphrodite plant has numerous bananas on it then it’s probably a good idea to just eliminate the whole plant, although in some cases it may be possible to just remove the male flowers using tweezers, if there are only one or two present. However, it’s important to be extremely careful when doing so, as the last thing you want is to accidentally spread some of the pollen.

Alternatively, if you notice male flowers starting to appear on female plants at the end of the flowering period then it could be a sign that its time to harvest, in which case you’ll want to start picking your bud without delay.

Of course, all of the above only applies if you are just trying to grow high-quality bud, and it’s a bit of a different story if you are actually attempting to breed plants. Obviously, male flowers are necessary for this purpose, so you won’t be eliminating these while breeding. It’s also here that hermaphrodite plants really come into their own, as the seeds produced from self-fertilised hermaphrodites always give rise to female offspring.

Commercial breeders therefore rely on hermaphrodites when creating feminised seeds, and often introduce chemicals like silver nitrate to deliberately stimulate the production of hermaphrodite inflorescences.

The rest of us, though, need to be on the lookout for any unwanted stamens on our plants, otherwise we could find our sinsemilla dreams are dashed by an undetected hermaphrodite.

[i] Holmes JE, Punja ZK. Hermaphroditism in marijuana (Cannabis sativa L.) inflorescences–impact on progeny sex ratios and genetic variation. Frontiers in Plant Science. 2020;11:718. – https://www.frontiersin.org/articles/10.3389/fpls.2020.00718/full

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Ben Taub