How To Sex Marijuana Seeds

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Are genetics the sole determinant of cannabis sex, or do growing conditions play a role too? Learn more in this article. Learn how to tell the difference between male and female cannabis plants, so you can properly sex your cannabis in the early pre-flower stage. When growing regular cannabis seeds the chances of them being male or female is 50/50. Find out how to tell the sex of you cannabis plant and ways to prevent any cross pollination happening.

Cannabis Sex: What Determines It?

Both genetics and environment play a role in the determination of the sex of a cannabis plant. Many growers focus on the growing conditions to ensure that hermaphroditism does not take place, but genetics play just as important a role.

Cannabis sativa L. is a dioecious plant – in other words, the male and female sexes are expressed in separate plants. With that being said, some cases of hermaphroditism are known to occur. The most desirable and psychoactive component of the plant is formed in the female flowers. Thus, knowing how to differentiate between male and female plants is integral to any grow operation, whether commercial or at home.

Male cannabis plants have their purpose, too. Even if the buds are not harvested for sale or consumption, male plants are imperative to a breeding program. For this reason, growers and breeders must know the differences between male and female plants and what determines this, especially to avoid hermaphroditism.

Which factors influence the sex of a cannabis plant?

How and why the sex of cannabis plants is determined is a subject frequently discussed by cannabis growers all over the world.

The determination of gender in human beings is simple: the male, who possesses both X and Y chromosomes, either gives or does not give a Y chromosome to the embryo. If it does, the child is born a male. If it does not, the child is born female. However, recent studies have shown that under stressful conditions, the male is more likely to produce spermatozoa containing X chromosomes.

In human embryos, a single X chromosome and a single Y chromosome denote a male (XY). Two X chromosomes denote a female (XX). The combination of genetics from egg and sperm create a diploid cell, containing two chromosomes.

In the case of cannabis, things are a little more complicated. While cannabis has been identified as having diploid cells, there are researchers producing tetraploid plants of cannabis for the purpose of improving its medical qualities. Tetraploid cells contain four chromosomes of either X or Y (XXXX, XXXY, XXYY, XYYY or YYYY). However, it is unlikely that tetraploidy occurs in cannabis in nature.

Generally speaking, in mammals, sex is determined at birth, with no interference on physical sex by developmental conditions. For example, even under stressful circumstances, a female reproductive organ won’t turn into a male reproductive organ. However, this does occur in cannabis. Therefore, the genetic make-up of the seed cannot be the sole factor involved in determining the sex of marijuana plants.

It is for this reason that some cannabis growers place more importance on growing conditions. Under extreme or poor growing conditions, there is a predominance of male plants. This is not so farfetched, as the main objective of a cannabis plant is to procreate.

Essentially, for a male plant to grow under adverse conditions is a defense mechanism of the cannabis plant, as one male can pollinate hundreds of female plants. The effect of growing conditions on both male and female plants will be discussed later in the article.

So as the understanding of cannabis cultivation has it, both nature (genetics) and nurture (growing conditions) influence the sex of the cannabis plant. But how exactly does this work?

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1. Nature: The role of seed genetics

As much as growing conditions play a vital role in determining the sex of cannabis plants, there is also plenty of genetic information stored in seeds. In the presence of optimum growing conditions, it is the seed genetics which will determine the sex of the plant.

Botanists and researchers of this 2004 study identify fragments of gene sequencing that determine the sex for both male and female plants. They also identified certain gene fragments which may play a role in the development of hermaphrodite plants. In any case, the results of this study show that the genetics of a plant play a role in determining the sex. The commitment to a specific sex takes place as soon as the leaves of the fourth node emerge.

Remember, this is different to determining the sex of a plant as a grower. Cultivators do not need genetic identification material to understand if their plants are male or female. Rather, certain signs in early plant life can be used by a grower to help them determine the sex of their plant.

2. Nurture: Growing conditions and feminisation

The feminisation of cannabis seeds is a perfect example of how cultivation conditions are also intrinsically linked to a plant’s final sex. Feminisation consists of taking a female plant and turning into a hermaphrodite by creating environmental stressors. At this point, certain female flowers will begin to produce pollen, which can then be used to pollinate the same plant. The final product is a feminized seed.

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Which external factors can affect which sex the cannabis plant manifests?

In general, plants that are subjected to stress around 3 weeks into vegetation are more likely to manifest male genetics. If stress takes place later on in vegetation or during flowering, a plant may be forced into hermaphroditism.

When humidity exceeds the optimum amount for cannabis, it is more likely that male plants will develop. In conditions with less relative humidity, it is more likely that female plants will develop.

Interestingly, the moisture of the soil is another environmental condition that can affect the sex of a cannabis plant. In soil that contains too little moisture, it is more likely that a male plant will develop.

The warmer the environment, the more likely it is that a male plant will develop. However, with that being said, it is possible that this stressor is linked with the photoperiod. In warmer climates, there are generally longer days and shorter nights, and the effect of temperature is inextricably linked with photoperiod.

In indoor cultivation programs, the grower may choose the colour of the light spectrum. The more blue light appears in the spectrum, the more likely that female plants will develop.

Finally, photoperiod is an important environmental condition that can affect sex. Shorter light hours per day usually results in more female plants, while longer exposure to light usually results in more male plants.

Ultimately, any grower can force a developed female plant into being a hermaphrodite by adjusting the environment. Changes in photoperiod, increasing the temperature, harvesting too late or over-fertilizing may all result in a female plant turning into a hermaphrodite. With that said, hermaphroditism may also occur as a result of genetics, as some strains are more prone to hermaphroditism than others.

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When plants are kept in the correct optimum environment for their genetics, there is generally a small likelihood of hermaphroditism unless the seed is genetically prone. This is why growers must pay close attention to the cultivation environment to avoid hermaphroditism.

Long story short: As almost always, it’s not nature and nurture. A combination of both genetics and environment play a role in the determination of the sex of a cannabis plant.

Laws and regulations regarding cannabis cultivation differ from country to country. Sensi Seeds therefore strongly advises you to check your local laws and regulations. Do not act in conflict with the law.

Sexing Cannabis: How to Tell the Difference Between Young Male vs Female Cannabis Plants

Are you growing cannabis at home, but aren’t sure if your plants are male or female? Then you’ve come to the right place! This article is going to show you how to tell the difference between male and female cannabis plants to properly sex them.

In particular, I want to show you how we determine the sex of our cannabis plants while they are still quite young. It gets significantly more obvious as the plants begin to mature and flower. On the other hand, it can be a bit more tricky to sex cannabis plants in the early pre-flower phase, but it is definitely possible! We’ll also talk a bit about why it is important to determine the sex of cannabis plants, the difference between regular and feminized seeds, how we treat our plants up until the time we know their sex, and what to do with unwanted male plants.

If you’re new to Homestead and Chill, be sure to check out our other cannabis-related articles! We primarily grow outdoors, 100% organic, and aim to provide helpful information that is easy to follow – both for new and experienced growers alike. As a disclaimer, this article is intended for those who can legally grow cannabis at home.

Feminized vs Regular Cannabis Seeds

If you are growing from feminized seeds, you shouldn’t need to worry about sexing your cannabis plants all that much. While not 100% guaranteed, there is only a very slim chance that a feminized seed will produce a male plant. About 1% in fact. In all of our years growing, we have never had a cannabis plant grown from feminized seed turn out to be a male – though we only grow a handful of plants per year. Folks who grow hundreds of plants could potentially end with a rare male now and then.

Feminized seeds are highly desirable to most growers. They’re efficient. It is almost sure-fire that you’re spending your energy and resources raising ladies. However, some growers accept or even prefer regular (unsexed) seeds! We grow a little of both.

Why grow regular cannabis seeds? Well, maybe a particular breeder or strain you want to try only carries regular seeds. Some growers feel that the feminization process is unnatural, and prefer to kick it old school by growing regular seeds only. Some enjoy the gamble and challenge. Whatever the reason, when you grow cannabis from regular seeds, the odds of getting all lady plants are not in your favor. You will end up with some males. Therefore, you need to learn to sex your cannabis plants! Also, we always start several extra “regular” seeds – assuming a 50/50 chance that some will be culled because they are male.

How are feminized cannabis seeds made?

Curious about how feminized seeds are created? In a nutshell: most feminized seeds come from cannabis plants that have been treated and altered in a manner that inhibits male chromosomes. The most common method is to spray the plant repetitively (daily or more) with colloidal silver. Other chemicals and compounds can be used too, but are far less accessible. Colloidal silver is technically “non-toxic”, but you do not want to smoke it! Thus, the plant is sacrificial – used for the production of pollen and seeds only.

Repeated colloidal silver treatments cause repression of the plant’s ethylene, which is the stuff that creates male flowers. Instead, the treated female plant will grow pollen sacks full of FEMALE pollen (XX rather than XY). Then breeders use the female pollen to pollinate female flowers, resulting in the development of all-female seeds.

Another way to create feminized cannabis seeds is called rodelization. It is a more natural but unreliable method, and less frequently used by breeders. Near the end of a growing season, an un-pollinated female cannabis plant will sometimes produce pollen sacks in a desperate attempt to pollinate herself. That pollen can be used to try to create feminized seeds, but because ethylene hasn’t been repressed, may also result in male seeds.

Okay, back to sexing cannabis.

Why Sex Cannabis Plants? The Role of Male and Female Plants

For the most part, the average home grower wants female cannabis plants. The ladies are the ones that produce the fattest, most resinous and most potent flowers – aka buds. Male cannabis plants are only desirable if someone wants to breed cannabis and save seeds (which is a whole other topic for another day). Even then, the grower will want to spot the difference between the male and female plants and separate them early on, unless they want free cross-breeding and pollination between many types of strains.

Not only are the males less desirable, but male cannabis plants interfere with the quality and production of your female plant. Males grow pollen sacks, and produce pollen. When a female cannabis plant becomes pollinated by a nearby male, her energy shifts into producing seeds.

Like most things in nature, female cannabis plants have a biological drive to reproduce. After the deed has been done, she will sit back and relax. While a pollinated female cannabis plant WILL still develop decent size buds, they are usually lower quality and contain less THC and other desirable cannabinoids. Not to mention, they’ll be full of seeds. When left un-pollinated, a female cannabis plant’s flowers (buds) will continue to swell, develop more trichomes and become increasingly resinous. She is trying to get as sticky and large as possible to catch pollen in the wind. That sweet sinsemilla – aka unfertilized, seed-free cannabis.

When to Sex Cannabis Plants

Our goal here today is to learn how to tell the difference between male and female cannabis plants early on, so you can get the males away from the females as soon as possible! It will help protect your lady plants – but also spare you the wasted time, resources, and energy of tending to male plants that you don’t intend to keep.

Keeping in mind that every strain and grow set-up (e.g. indoors, outdoors, daylight hours) creates varying circumstances, most cannabis plants begin to pre-flower as early as 4 weeks after germination. By week 6, the pre-flowers begin to reveal their gender and you should be able to identify the sex using the tips to follow. Once the plants go into full flower (8 to 10 weeks on average, for a natural outdoor grow) the differences between male and female plants will be glaringly obvious. We’ll talk more about exactly what each sex looks like in a moment.

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Until we can tell the sex for sure, we continue to treat the plants equally. We start our seeds in small 4-inch nursery pots. About two weeks after germination, we pot the seedlings up into an approximately two-gallon (trade size) “sexing pot” like these BPA-free nursery pots. This enables everyone to continue to grow in a happy and healthy manner for several more weeks*. Then, once we can surely tell the difference between the male and female cannabis plants, only the ladies move into their forever home – 15 to 25 gallon grow bags full of recycled organic living soil. To learn more about our soil recipe and how we maintain it, see this article.

*Note that our feminized seedlings go from a 4” pot to an 8” pot, and then more quickly into large grow bags, using less soil in the potting-up process.

This little girl (or boy) is far too young to tell, but needs to be potted up soon. The two in plastic pots in the background were determined to be male and culled the next day. The two on the left in grow bags are definite females (one from feminized seed, and one we sexed from regular seed).

How to Tell the Difference Between Male and Female Cannabis Plants in Pre-Flower

In order to correctly sex cannabis plants, you’ll need to become familiar with their anatomy in general. Both males and females produce pre-flowers and flowers in the junctions between stems or branches. The very first pre-flowers show up in the crook between the main plant stalk and a fan leaf stem (petiole), usually near the top of the plant. The good news is, the males usually begin to develop and show sooner than females. I guess the idea is that the dudes want to have their pollen ready and waiting for when the ladies join the party?

Look for plant pre-flowers at the higher stalk/branch junctions, as described above. If needed, use a jeweler’s loupe to get a better look! That is the same magnifying tool commonly used to examine trichomes and determine plant readiness for harvest. Then, locate the stipule, which is a leafy pointed flap that protrudes from the junction. Don’t confuse that for a pre-flower! The cannabis sex parts are located just behind the stipule. Behind the pre-flower sex parts, taller growth tips will emerge – future auxiliary branches that produce buds.

Identifying a Male Cannabis Plant

Very early, the male pre-flower (early pollen sacs) simply looks like a more round version than the female pre-flower part. It is often referred to as a “spade”, like the spade suit in cards – squatty with a bulbous bottom and very slight tip. As it becomes slightly larger, the male pre-flower resembles a ball at the end of a stick. The male pre-flower is called a staminate. Then, the staminate eventually develops into a long hanging sack of baby bananas – the pollen sacs. Hopefully you can ID and cull the males before they get to this stage.

A 4-5 week old male cannabis plant in our garden, showing his stick and ball. Note that this is a really early and obvious example. Most of the other males in this age group show a round ball, but protruding less and more nestled flat against the stalk.

A more advanced male pre-flower, courtesy of Dr. Weedly (We never let our males get this far to photograph)

Did someone order a banana hammock? The male flowers are about to open and shed pollen, if they haven’t already. Photo from Green Cultured

Identifying a Female Cannabis Plant

In contrast, the very early female cannabis pre-flowers are more ovate in shape: pear-like, but with a longer slender pointed tip. That is called her calyx. Extending from the tip of the calyx may be a pair of pistils, or white hair-like protrusions. However, please note that not every female cannabis plant in pre-flower produces pistils.

If you are still unsure of the sex of your cannabis plant, wait to make any drastic decisions! Yet if you’re fairly certain, consider some of these other common differences between male and female plants. Perhaps it will help you more confidently make a decision.

Other Common Differences Between Male and Female Cannabis Plants

Aside from the clear-cut flower differences, there are a few (potential) trending characteristics between male and female cannabis plants. In many cases, male cannabis plants tend to be more gangly. They may be tall, narrow, have fewer fan leaves, and longer spacing between branches – also referred to as greater inter-nodal spacing. On the flip side, female cannabis plants are usually more compact and bushy than males.

Please keep in mind that these traits are not guaranteed, and shouldn’t be the only way to sex cannabis plants! Variations among strains and phenotypes can lead to all sorts of crazy things. The general plant structure simply may help give you a clue if you’re on the fence.

My Cannabis Plant is Male! Now What?

I hope you started a few extra seeds, and have plenty of ladies left to grow! Once you determine that you have a male cannabis plant, get rid of it. Again, unless you want pollination and seeds, it is best to cull the males as early as possible. Simply separating the plants isn’t enough. Even if you relocate the male plant to another part of your yard, the pollen can carry in the wind. There are stories of female cannabis plants becoming pollinated from neighbors growing several blocks away.

However, the culled males don’t need to go to waste! One option is to chop up the male plant and use it to mulch other plants – much like we do with borage, fava bean greens, yarrow, and comfrey. You could also juice the leaves, which are full of nutrients. Heck, you could even steep the plant material in water to create a natural fertilizer as we do with stinging nettle. Finally, I’m sure your compost pile will welcome the male plant with open arms. Or would that be… with open worms?

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And that is how you determine the sex of cannabis plants.

In closing, I hope this article is interesting and useful in your homegrown adventures. Please feel free to ask questions in the comments below, and spread the cannabis sex love by sharing this article. Even if you like to grow mostly feminized seeds, don’t you find this stuff fascinating? I sure do. Thanks for tuning in and nerding out with me a bit. Best of luck this growing season!

How to sex marijuana plants

Regular cannabis seeds will generally develop into both male and female plants. If you’re unlucky, you may end up with the odd hermaphrodite plant. You need to remove both males and hermies as quickly as possible. Males don’t carry bud and you don’t want them fertilizing the females which do. Hermies do carry bud, but it’s very low quality. They also carry pollen and so can fertilise productive females. Basically, they’re more hassle than they’re worth. The best time to sex marijuana plants is during pre-flower. This is when they first become identifiable as male or female.

Beginner tip

If you are new to sexing marijuana plants, you probably want to start with a maximum of five seeds. Stick to the one strain, so you can easily compare your plants. You also want to leave plenty of space in your growing room so you can physically move plants. This will allow you to “sex in stages”. In other words, if you’re sure a plant is male you can just remove it. If you’re not sure, then you can separate your plants into “females” and “not sure”. Keep them far enough apart that there is no chance of pollen from the “not sures” reaching the females. Then you can work on definitely sexing the “not sures”.

Bonus tip

Statistics can play tricks on people. In principle, regular seeds have a 50/50 chance of being male or female. If you only sow one seed, then it can only be one sex or the other (unless it hermies). If you sow more than one seed then you may or may not get a mix of genders. The more seeds you sow, the more likely it is that you will end up with a mix of genders. It is, however, not guaranteed. You could still end up with all male plants or all female plants. Remember this when you are sexing your marijuana plants. Basically, go by what you see rather than what the statistics suggest you ought to have.

How to sex marijuana plants

Frankly, the easiest way to sex marijuana plants is to use feminized seeds. If, however, you want to do it the “old-school” way, here’s what you need to know.

Step 1 – Go online

Look for videos showing the difference between a male cannabis plant and a female cannabis plant. If at all possible, look for videos which relate to the strain you’ve chosen. If you can’t find any, look for a comparable strain. In other words, if you’re growing a strain which is 80% Indica dominant, look for someone else growing a strain which is 80% Indica dominant. Then go and look for close-up images of the key parts. Yes, it will be different when you do it yourself. In fact the first time, you may find it a bit of a challenge. Looking at online resources, however, can definitely be a big help.

Step 2 – Stand back and look at your plants from a (bit of a) distance

Before you get caught up in details, take a look at the bigger picture. Male plants tend to grow quicker than females. They also tend to be slimmer and have less foliage. This is, of course, all relative. A male Indica is never going to be as leggy as a female Sativa. A female Sativa is never going to be as bushy as a male Indica. That’s why you want to stick to one strain at first. Then you can make like-for-like comparisons.

Step 3 – Look for pollen sacks

Pollen sacks look, quite literally, like tiny balls. They can be seen with just the naked eye. Having said that, a magnifying device can make the task a whole lot easier. If you see a pollen sack, then a plant is definitely male. If you don’t it may be female. Alternatively, it may still be in the process of development.

Step 4 – Look for pistils

In the pre-flowering stage, pistils are tiny white hairs. They are virtually impossible to spot without a magnifying device. Even with a magnifying device, it can be a challenge to see them at first. Later, as flowering continues, the pistils will become both very colourful and very obvious.

Step 5 – Clone the “not sures”

Take a cutting of the “not sures”. Let it grow for a few days. Then force flowering. The sex of the clone will also be the sex of the host. This trick is 100% accurate – as long as you keep accurate records of what cutting came from what host.

What is a hermaphrodite cannabis plant?

Hermaphrodite plants develop both male and female sexual parts. Hermaphrodite weed is lower in both quantity and quality than regular bud. Sometimes it’s still usable. Sometimes it’s only fit for the (composting) bin.

There are some strains which are frankly notorious for hermying. Reputable seed banks will mention this in their descriptions. You can also double-check with independent strain reviews. These strains are best left to the most experienced growers.

In general, most strains will only hermie if they are exposed to excessive stress. The big five causes of hermying are: ventilation, lighting, temperature, hygiene and handling.

Out of these, ventilation is usually the biggest issue. The reason for this is that it causes so many other problems. For example, poor ventilation means that your plants are too close together. This makes it hard for them to capture sufficient light and easier for them to overheat. It makes it harder for the grower to keep the growing room clean and easier for any problems to spread from one plant to another. Last but by no means least, it makes it harder for the grower to handle the plants appropriately and so easier for them to be damaged.

In short, if you choose a robust strain and remember your marijuana basics, then you should be able to avoid hermies. The less experience you have, the more important it is to choose a strain with solid genetics. Again, reputable seed banks will generally highlight strains which are particularly suitable for beginners. You can also check online for independent strain reviews.

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