A hermie is a female cannabis plant that will produce male parts, pollen sacks. There are a number of reasons for this, i will cover some below.
First a little about the sex of cannabis plants. Like most living things cannabis plants need both a males and female to reproduce. Males plants are undesirable as they don't produce the buds we all love.
Males serve some purposes though. If you choose to breed cannabis you will need pollen, a male plant can be harvested for its pollen, that pollen can be used straight away or stored. I'll not go into breeding here but will cover it in another topic.
Female plants can also produce pollen, this can be done several ways, most of the time by accident, causing pollination of your crops. This is what we call a hermie. This is something that unless you want to happen can be a disaster, female plants that are pollinated will put their energy into producing seeds, not the THC that we need to get high. Bud that is not pollinated, contains no seeds is called sinsemilla. A plant may also produce "bananas", these develop in flower and will pollinate surrounding areas of bud if not removed quickly.
Observation is key here, being able to notice and deal with this very quickly is so important. Unfortunately once a plant shows signs of hermie there isn't much that can be done, its now genetically wired to produce these part and more often than not will continue to do so.
A female plant that has produced pollen sacks.
A female plant that has produced bananas.
There are many reasons for a plant to hermie. 99% of come down to stress. A plant is of course a living thing, like most living things its main drive is to reproduce. If a plant thinks it is under attack, its life cycle is coming to an end, or just isn't a happy camper it will try to reproduce, even if it is a female, nature always finds a way!
Below ill go into some of the more common reasons plants will hermie due to stress:
Health of your plants:
Continuous issues regarding the health of your plants, deficiencies, pH fluctuations, root issues, pretty much any issue with your plant if severe enough or frequent will cause a plant to hermie.
Temperature:
Keeping a consistent temperature is important, There are many opinions on perfect temperatures for cannabis but most will fall between 18-29c, the lower end at night the higher during lights on periods. Extreme fluctuations in temperatures will stress a plant, make it think the seasons are changing etc. This may cause a hermie.
Genetics:
This can play a role, some strains, or phenotypes will be more likely to hermie under stress. You could just be very unlucky and germinate a seed that is already wired up to to hermie, this is very uncommon though. Breeder do/should go to great lengths to stress test a strain before it is made available to growers. Female seeds are produced by causing a plant to hermie after all, but ill cover that in another topic.
Lighting issues:
Inconsistencies in lighting, more specifically the amount of light and dark your plants get will stress a plant. It is very important that once you set your timers to give the required amount of light for the stage you are at you don't mess about with it.
Dark!:
Interruptions in your dark period are one of the most common reasons for a plant to hermie. Going into your grow area during dark hours should be avoided at all costs. Light leaks are another major factor in plants that hermie, you should ensure your grow area is sealed from light leaks, a good way is to get inside you grow area and seal it, making sure lights are on in the room it is situated, any light leaks should be sealed before growing plants.
Light burn:
We all like lots of light in our grooms, lots of light will normally mean a bigger harvest, but to much light can stress a plant.
Life cycle:
Here comes that term again...Nature always finds a way! Many plants if not harvested at the correct time will try to reproduce as they come to the end of their life cycle, yes, even a 100% female plant. Leaving a plant for to long before you harvest is risking a hermie. Not only that but you will also be missing the perfect time to harvest your plants to get the best from your bud.
To see when is best to harvest your plants follow this link: viewtopic.php?f=12&t=47
So...As you can see there are many reasons a plant can hermie, mostly down to stress, yes, you can just be unlucky but this is very rare. Look after your plants and they will look after you!
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