Table of Contents
by Nebula Haze
Remove plants with both male pollen sacs and female flowers (hermies) to avoid pollination/seeds!
You may also see yellow “bananas” (stamens) growing around the pistils/hairs of the buds. A stamen normally grows inside a male pollen sac but sometimes appear directly on female buds, especially in times of stress. A stamen produces pollen and doesn’t even need to open up before it starts making seeds! Remove plants immediately if they start growing bananas (also referred to as “nanners”) or your entire grow room may get pollinated. No one wants to be surprised by seedy buds after harvest.
This highly stressed plant (from heat and too much light) grew a banana in a last desperate attempt to make seeds
Certain cannabis plants will herm even if healthy and unstressed. This is a genetic trait carried by some strains and particular plants. That’s part of why it’s important to grow seeds from a trustworthy breeder. For example, every clone of the following plant grew bananas in week 3 of the flowering stage, under no stress, in multiple different grow setups. When herming is part of a plant’s genes, there’s not much you can do.
These bananas weren’t triggered by stress. Herming is simply part of this plant’s genetics. The brown hairs are already pollinated.
Here’s a closeup of a herm banana
This poor hermie has male pollen sacs growing among the female flowers. It’s recommended to immediately toss any plant that shows both male and female flowers!
Cannabis Life Stages and Sex
Did you know there are “male” and “female” cannabis plants? Cannabis plants are “dioecious” plants, which means each plant shows a particular sex, just like humans and many animals. There will occasionally be plants that show mixed-sex and these plants are often referred to as hermaphrodites or “hermies”, which I will explain in much greater detail below.
The sex of a particular plant matters quite a bit to growers. That’s because only female cannabis plants produce buds. In fact, the “buds” that we smoke are actually the female flowers of the cannabis plant.
The highest quality bud is considered to be “sensimilla” and refers to female cannabis buds that have not been pollinated by a male cannabis plant. The word “sensimilla” actually comes from the Spanish phrase “sin semilla” which roughly translates to “without seeds.”
Regular marijuana seeds will usually be about 50% male, and 50% female. That means half of the seeds will be unusable as far as growing buds. Please note that some male cannabis plants (about 70% of male cannabis plants according to some estimates) may produce a small amount of useable THC via trichomes growing on the outside of the plant. Unless you’ve seen the males in your plant’s family tree, there is no way to know for sure if a particular male plant is going to produce THC/trichomes. Even if it does it will be a much, much lower amount than a female cannabis plant producing buds.
If you have a male plant and you are trying to grow bud, I strongly, strongly recommend throwing the male plant away immediately and starting another seed or focusing on your other plants. It’s a waste of time to grow male plants for THC or other cannabinoids – they don’t grow buds!
Here’s a picture of a male cannabis plant – no buds or trichomes, just pollen sacs!
Quick Tip: How do you make sure you only grow female plants so all your plants produce buds?
One way around the issue of having 50% male and 50% female plants is to purchase feminized seeds online. These seeds are available from all reputable online seedbanks, and the plants produced by these seeds are always female. Get your questions about buying seeds online answered! You can also make your own feminized seeds, but you have to start with two known female cannabis plants.
It’s difficult to look at a young cannabis plant and know its sex
For the first part of your cannabis plant’s life, it will be in the first stage of growth known as the “Vegetative Stage.” In this stage, your plant will only grow leaves and stems, but no buds or flowers. Think of this as the time when your plant is gaining size to prepare for the second stage of life.
A young vegetative cannabis plant is unlikely to reveal its sex until it’s at least 3-6 weeks old, and sometimes even later than that.
Unfortunately, it’s difficult to determine the sex of a cannabis plant when it’s a young seedling. Although there is genetic testing that can be used on plants as young as 1 week old, most growers aren’t going to go that route. At a certain point, most strains will “reveal” their sex via pre-flowers at the joints. This can occur as young as 3 weeks old with male plants, and around 4-6 weeks old for female plants. This is normal and is just a sign that your plant is fully mature and ready to start flowering. Learn more about preflowers.
Another great option is to use clones. Cuttings (clones) taken from a female plant will always turn out to be female. Sometimes clones are showing preflowers by the time they’re rooted as a clone. We also know that when you breed two female plants together, you end up with feminized (all-female) seeds.
So, unless you start with a known female clone or feminized seeds, there’s no way to know what sex your plant will turn out until it actually starts showing signs of sex organs. This happens in the second stage of your plant’s life, known as the “flowering stage.” The first sex organs that appear are often called “pre-flowers.”
When do cannabis plants reveal their sex?
In addition to looking for preflowers, all cannabis plants reveal their sex when they reach their second stage of life, known as the “Flowering Stage”.
The first sign of sex almost always appears at the “V” where new growth tips form from a stem, like this….
See the little growths appearing at the “V” or “crotch” where the growth node meets the stem? These are the first sign of “pre-flowers“. In this case, we can see the pre-flowers are forming, but it could be tough to tell whether this plant is going to turn into a boy or a girl quite yet. (Note: It’s a boy)
Younger plants (that are less than 6 weeks old or haven’t shown preflowers yet) tend to take a little longer to switch into the flowering stage compared to older, more mature plants that have been vegetating for a while. Other than that, you can pretty much force a cannabis plant to start flowering no matter the age, even 2-3 weeks after the seed was germinated.
Read the full article about male vs female cannabis plants (and learn how to use cloning to identify the sex of young plants while they’re still in the vegetative stage – advanced only!): https://www.growweedeasy.com/marijuana-boy-girl
So now you know that most cannabis plants are normally considered to be either “male” and “female.” Yet sometimes you will run into plants that show both male and female characteristics, and these plants can accidentally self-pollinate, or pollinate your other female plants.
A cannabis plant that shows both male and female parts is often referred to by growers as a hermaphrodite or “hermie.” These can pollinate your plants and cause seedy buds.
There are a few different types of mixed-sex plants, and it’s important for a grower to understand some of the biggest differences so they make the best decision possible when faced with hermies.
Important: It’s not advisable to breed mixed-sex plants to create seeds because their offspring are more likely to display hermie characteristics.
Although growers will refer to all mixed-sex plants as “hermies,” there are technically two different kinds: hermaphrodite cannabis plants, and mixed-sex buds (like buds with nanners). The only reason I bother to differentiate between the two is that true hermaphrodite plants are more predictable.
With a “true” hermaphrodite plant, the male and female parts will grow on different parts of the plant. They won’t grow together in the same spot such as when nanners appear in the middle of buds.
Here is an example of a true hermaphrodite plant – notice how this hermie has both female pistils and fully formed male pollen sacs
What causes it? Stress can trigger this type of hermaphroditism, but unlike bananas, this particular type of mixed-sex plant seems to be a little bit more stable based on the plant’s genetics. It usually doesn’t take stress to cause these to appear. They’re more like a natural trait of the strain. A clone of a true hermaphrodite plant will often also turn into a hermaphrodite, and offspring will often show the same traits even under perfect environmental conditions.
It is recommended to never breed a plant that shows hermaphrodite traits since this is a highly inheritable genetic trait. A good “breeding stock” mother will not show signs of hermaphroditism even when subjected to stress.
What should the grower do? It is recommended that you remove hermaphrodite plants from your grow room or grow area as soon as possible to prevent accidental pollination of the buds.
If pollen from a pollen sac is allowed to make contact with your buds, those buds will stop focusing on making more buds and will turn all their “effort” into making seeds. No one wants seedy buds and reduced yields!
Unlike bananas, hermaphrodite plants tend to be more predictable. Though it’s not advisable, a grower who watches very closely can carefully pluck all pollen sacs before they’ve burst. However, this should only be done if it’s the only plant you have! Don’t do this if you have other female plants that can be pollinated!
Remember, while these pollen sacs can start appearing early, they may continue to appear throughout the flowering stage so stay vigilant!
The following type of hermaphrodite plant has mixed male and female parts, referred to in botany as “bisexual” flowers.
With mixed-sex buds you will see plants that grow a mix of pistils and pollen sacs together, like this…
Another common type of mixed-sex buds is the type that produces “bananas” (sometimes called “nanners”) which grow from the middle of female buds.
Example of a “Banana” or “Nanner” growing among buds
Bananas are rarely round and they don’t look like a normal pollen sac. Instead, they’re often elongated and yellow, which is where they get the nickname “banana”. They also often grow together in bunches that can look like a bunch of bananas. Occasionally they appear more lime green than yellow.
Sometimes a banana appears lime green instead of yellow
These can be a lot more difficult to control than actual pollen sacs, since they may start pollinating everything in the area as soon as they appear. A few bananas won’t do much damage, but if you have a big banana problem it may be best to harvest the plants immediately and cut your losses. Seeds take some time to develop, so if a plant starts herming right around harvest time, it’s less likely you’ll end up with seeds.
What are they? Bananas are actually the exposed “male” parts of a pollen sac, called the “stamen” which would normally be surrounded by a sac to hold all the pollen until it bursts open. If you open up a fully formed male pollen sac, you will see what looks like bananas (stamens) inside.
But when bananas appear on your plants, they don’t need to “burst” in order to spread pollen, they will immediately start making pollen and often will seed the buds that are close by even if bananas are removed right away, and sometimes the pollen can drift to other plants and pollinate them as well, too.
It’s possible that the pollen is sterile, and won’t pollinate bud successfully…but don’t rely on that happening!
The yellow bunches in this bud are bananas/stamens and will “try” to pollinate everything they can – they don’t have to wait for a pollen sac to burst. It’s possible that the pollen is sterile, but often you may find seeds.
If a female plant is allowed to go too long without being harvested or pollinated (allowed to go past the point of optimal harvest), she will sometime produce a bunch of bananas in her buds as a last-ditch attempt to self-pollinate and create seeds for the next year. This is sometimes known as rhodelization. This is not as destructive as other types of hermies since it only happens after plants are already past the point of optimal harvest.
What causes it? While genetics are ultimate the cause of whether a plant is capable of producing bananas and mixed-sex buds, environmental stress is often a big component in causing bananas to form. Luckily if you stick with high-quality genetics, you are much less likely to run into bananas even if you do accidentally stress your plants. Not all bananas are “fertile” and you may see them without ever getting seeds.
Male hermie banana growing among the beautiful buds 🙁
What type of stress can trigger bananas to form on cannabis buds?
Inconsistent Light Schedules & Light Leaks – When plants don’t get light at the same time each day, or if they’re exposed to light during their dark period (light leak). For photoperiod plants, this might be the largest contributor to hermies.
Temperature – When temps get too high, hermies and nanners often appear. Cold night temps, or just large temperature swings in general, are also known to trigger bananas for some strains.
Too-Bright Light – Like too much heat, and/or light that is too bright can stress your plants and trigger hermies. This is most often caused by growers keeping their lights to close to their plants. You can light-burn your plants even when the temperature is under control.
Genetics – While stress plays a big role in the formation of bananas, the tendency to form them is genetic. This tendency is very common in the seeds of a plant that hermied. “Feminized” seeds, while always female, are much more likely to show the same herming traits as its parent. Growing seeds that were produced this way is naturally selecting to produce more buds that grow bananas. Only get feminized seeds from a trusted breeder.
What should the grower do? It is recommended that you remove plants showing bananas from your grow area immediately to prevent accidental pollination of buds. If the pollen being formed is allowed to make contact with your buds, those buds will stop focusing on making more buds and will turn all their “effort” into making seeds. If the plant self-pollinates, you will end up with a bunch of sub-par seeds that are likely to have the same problem.
Of the different types of “uncertain sex” cannabis plants, plants with mixed-sex buds (especially hermies with bananas) are the least predictable and this can make them more likely to cause unwanted pollination. This is partially because bananas may be hidden in the buds, and they don’t have a pollen sac that needs to burst to pollinate buds – it will start pollinating almost immediately.
A grower who watches very closely can carefully pluck all bananas, but they are unlikely to be successful and will probably end up with at least a few seeds.
Trying to salvage a plant that has started producing tons of bananas is NOT recommended, because it’s hard to get them all and you’ll end up with seeds. Even worse, once a plant gets started, bananas can appear in huge bunches overnight especially when the plant is stressed. Harvest the plant as soon as you can, before seeds get a chance to start forming.
This section will explain what you can do as a grower to reduce your chances of running into hermies or bananas in your grow room…
1.) Avoid Inconsistent Flowering Light Periods & Light Leaks
Keep indoor lights on timer, and avoid changing the light schedule during the flowering stage if possible.
Prevent outdoor plants from being exposed to street lights, flood lights or other types of artificial lights during the night.
Respect the dark period – In the flowering stage it’s important to make sure all your plants (except auto-flowering strains) get at least 12 hours of uninterrupted darkness every night. Avoid shortened dark periods and light leaks!
No matter the strain, try to keep your plants on a consistent schedule throughout their lives, as this helps them set their circadian rhythms.
And for photoperiod plants in the flowering stage, do not interrupt the plant’s 12-hour dark period with light for any reason.
Why? During the dark period your plant is “counting” the hours until sunlight appears, and interrupting this process is one of the most common ways to stress the plant into producing bananas or hermies. It can also cause your plant to revert back to the vegetative stage.
Along with the point above, make sure you do not have any light leaks in your grow space, which could allow outside light to sneak in during the dark period. During the dark period your plants like complete darkness.
If anything ever happens with your timer or power that causes your plant to get too much light or darkness, it’s important to correct your timer as soon as possible. But don’t worry about it too much if it happens just for one day. It’s usually okay if it happens only once, but be careful not to let it happen again since messing up the light schedule can cause hermies. It’s better for a plant to get a too-long day than a too-short night period in the flowering stage. So, for example, it’s better for it to get an 18-hour day than a 6-hour night. Cannabis plants “count” the hours of the night period, so it’s most important to make sure the night period is at least 12-hours long (longer is better than shorter for night periods).
2.) Maintain Proper Temperature Through Flowering Stage
Maintain a comfortable temperature in the flowering stage, between 65-85°F (18-30°C).
Avoid big temperature swings – temps should be slightly cooler at night than during the day.
- Don’t let the plant (and their roots) sit directly on a cold floor.
Always use “hand-test” to make sure it doesn’t feel too hot in the top canopy of buds under the light. Put one of your hands (palm facing down) under your grow lights where the top of your plants are located and wait 10 seconds – if it feels too hot for your hand it’s too hot for the plants! Be careful of cold drafts at night in cool climates during the winter.
Learn more about temperature here: https://www.growweedeasy.com/temperature-growing-cannabis
3.) Don’t Give Your Plants Too Much Light (Light-Burn)
While generally more light is better for your cannabis plants, very high power brightness can light-burn your plants, which stresses plants, causes unwanted bleaching, and can trigger the plant to hermie on you.
With high power LED grow lights and big HID lights, make sure to always follow the manufacturer’s specifications as far as the minimum distance from the top of the plants!
Don’t keep your lights too close because even if the heat is under control, too much brightness can cause stress too.
Light-burn is only common with high power LEDs (3W chipsets and bigger, x-lens technology, COBs, etc.) and big HIDs or perhaps multiple smaller HIDs (usually with an intense cooling system).
It is more difficult to “light-burn” your plants with fluorescent lights, CFLs, smaller HIDs, etc. – with these lights, you only need to worry about heat.
4.) Prevent Major Plant Problems
Major stress to the plant can cause the plant to react in unpredictable ways, including producing bananas and male pollen sacs. Major stresses include…
Major nutrient deficiency
Nutrient Burn – given too much nutrients
Total leaf loss (usually as the result of overzealous defoliation or bugs)
Any other huge stress to the plant
Want to read about a real example?
The plant pictured to the right was subjected to cold temperatures and then grew directly into the grow light, putting it under a lot of stress.
From the grower Saberabre: “So I left this girl (or what I thought was a girl, notice the pistils at the bottom calyx) over the weekend and came back to the plant up in the light getting burned. Yikes! I’m not too sure what happened here but it got pretty cold the last few days. I think it’s a hermie…”
A few days before this pic, the plant was just showing a few white pistils and appeared to be female.
After the stress that it went through, the grower came back to a plant that was completely covered in male pollen sacs, with the first few white pistils being the only sign of this plant is female.
5.) Always Start with Trusted Genetics
Hermaphroditism and mixed-sex buds seem to be more common when growing plants from bagseed (seeds that you find) or seeds from an unprofessional breeder.
The reason is that seedy buds are worth less than sinsemilla (unseeded buds). Therefore, if you find a seed in your bud, it likely was the result of either bad growing practices (male plants weren’t removed in time) or due to some type of problem (plants were stressed and self-pollinated, which means the next generation is most likely to do so).
When you’re buying seeds from a trusted breeder, they go to great lengths to prevent unintended pollination, and they specifically select for plants that don’t ever show mixed-sex traits.
And remember… even if you do everything right, sometimes you will run into hermie plants – it’s just a fact of growing. Sometimes these things just happen, for example…
“I’ve always felt like seeded weed was not nearly as potent as sinsemilla and I do everything in my power to kill all males! Cannabis is so sneaky, though – last summer we had such wild weather that even a couple of clones turned out some male sex parts.”
~ Experienced outdoor grower
“Cannabis has both male and female plants. When both female and male flowers are in bloom, pollen from the male flower lands on the female flower, thereby fertilizing it. The male dies after producing and shedding all his pollen. Seeds form and grow within the female flowers. As the seeds are maturing, the female plant slowly dies. The mature seeds then fall to the ground and germinate naturally or are collected for planting the next spring.
“Unpollinated, female cannabis flowers continue to swell and produce more resin while waiting for male pollen to successfully complete their life cycle. After weeks of heavy flower and cannabinoid-laden resin production, THC production peaks out in the unfertilized, frustrated sinsemilla!”
~Jorge Cervantes in Indoor Marijuana Horticulture