Sexing Weed Seeds

Are genetics the sole determinant of cannabis sex, or do growing conditions play a role too? Learn more in this article. Male vs Female Cannabis Cannabis is a dioecious plant, which means it has male and female flowers on separate plants. When the male plant enters the reproductive stage, it will develop male pollen sacs. The female plant will produce flowers ready to accept the pollen. This also means that cannabis is not true to seed, When sexing cannabis plants, most growers separate the plants by gender as the flowering stage begins. Avoiding pollination is key for a successful harvest.

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.

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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.

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 Seeds

Sexing cannabis seeds is vital for success. Whether a sensimilla grower or seed breeder it is important to know the boys from the girls.

Male vs Female Cannabis

Cannabis is a dioecious plant, which means it has male and female flowers on separate plants. When the male plant enters the reproductive stage, it will develop male pollen sacs. The female plant will produce flowers ready to accept the pollen. This also means that cannabis is not true to seed, i.e. seeds from a cross pollination will not directly represent the flowers they originated from and instead contain genetic material from both the mother and father plant. Because cannabis has both male and female sexes, you need to identify and understand the differences. Cannabis gender cannot be identified by seed or growth patterns and the only reliable method is to observe the reproductive organs that develop.

Growing for weed or seed

When you begin your growing journey, you will need to decide what your goal is. If you want to grow flowers for consumption or processing, you will want to ensure you only grow female plants that do not get pollinated. Seedless cannabis flowers are referred to as sensimilla and are more potent and flavourful than seeded cannabis flower. This is because when the female plant is pollinated, it stops directing energy to producing oils and cannabinoids. Instead, the pollinated plant focuses all its’ energy on producing seeds. Seeded cannabis is undesirable for medicinal and recreational growers yet it is first prize for many hemp and food crop growers, as well as breeders.
If you want to create seeds, you need to grow both female and male plants. You can separate your male plant as it starts to produce pollen. Then collect the pollen and pollinate only one or two branches on your female plant. By doing this you can enjoy the fruits of your labour and produce seeds for the next season. The other option is to simply let a male or two pollinate all the plants over the growing season. Leading to a harvest of hundreds to millions of seeds.

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Sexing Cannabis Seeds

The best way to identify your plants gender is to wait until it is sexually mature and inspect the nodes or growth points. Plants show sexual maturity by displaying alternate branching and “pre-flowers”. These traits begin in the early flowering stages or late vegetative stages. Pre-flowers are reproductive organs that begin developing before the plant fully enters the reproductive stage and can be used as early identifiers. Male plants produce pollen sacs which look like round balls hanging off the plant.

Female plants produce bracts and white hair like pistils. Pollen sacs are rounder in structure where bracts appear more angular with a thin white pistil growing from within. It is wise to wait until you are entirely sure of your plants’ sex before deciding what to do with it. Not all plants produce the same looking organs and early identification can be tricky for some cultivars. Paying careful attention at all stages of growth will ensure that you are able to far better control the quality and results of your grow.

Cannabis sex isn’t that simple

As if cannabis isn’t woke enough, it can also occasionally be gender fluid. In cases of poor genetics, stressful environment or purposeful reversal, the cannabis plant can display both sexes at once. This is called an intersex trait or “hermie”. Hermies are traditionally undesirable as they may seed crops that are intended to be seedless. Thereby greatly reducing the value of the crop.

However, in recent times breeders have perfected the art of using these traits to their advantage. Femisied cannabis seeds are created by forcefully introducing intersex traits in a female plant. Then using its pollen to pollinate other stable clones of the same female plants. This means that the seeds made from the cross will be identical to the mother plant and almost always female. These are known as feminized seeds. Nowadays most breeders will use chemicals to induce this change in the plant, however almost any stress of the right intensity can induce intersex traits across the spectrum.

It’s easier than ever

Always ask first. If you are unsure about sexing cannabis seeds, there are many online resources you can draw from. Facebook groups make a great place to share and learn from others. Similarly online forums are an excellent resource to browse and interact with other growers without compromising your anonymity. But be warned, there are as many unhelpful opinions as there are helpful. As not all comments are from experienced growers. Try and find a community of people whom you feel comfortable with and have a healthy track record.
You should always source your genetics from reliable and trustworthy providers. There are few things more frustrating than finding an unwanted hermie a few weeks from harvest. In South Africa it is now very easy to access high end and reliable genetics. Whether you want to start from seed or clone, there are multiple vendors supplying feminised seeds and clones. For the aspiring breeders, some vendors even supply regular seeds and male pollen that you can apply at your convenience.

Get the right grow gear

There’s an old proverb about not building your house on the sand and how you should plan for success. Growing A+ cannabis requires a dedication and flexible budget for the happiest results. Don’t be afraid to invest a little bit in the correct grow medium and nutrients, it will make all the difference.
We hope that we have taken some of the mystery out of sexing cannabis seeds. Honestly though, it will be surprisingly easy to get the hang of sexing cannabis seeds in no time at all. You will spot the signs and differences quickly with a well-trained eye and should be well on your way to beautiful big buds. If you still need a little help spotting the boys from the girls? Please contact our grow pros for some top shelf advice.

Sexing Cannabis: Is My Plant Male or Female?

Sexing cannabis plants is a crucial step for a successful harvest. Many new growers feel nervous about determining the sex, as experience does count. However, knowing exactly what to look for, setting the correct light schedule and giving plenty of attention is all it takes. A magnifying glass will come in handy, as the sex organs are super tiny.

Why is sexing cannabis plants important?

A cannabis plant typically produces either male (pollen-producing) or female (seed-producing) flowers. Cannabis grown with the intent of harvesting THC-rich buds requires non-pollinated female plants. In that case, keeping the sexes separate is vital. It takes just one male plant to fertilise a whole room of females, so act quickly.

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How to see if your cannabis plant is male or female

Around 6 weeks after germination (outdoors), or 1 week after initiating the flowering stage (indoors), the tiny buds (sex organs) begin to develop at the nodes of your plant. The male plants will develop pollen sacs that resemble a bundle of balls. These can appear a week or two before female flowers, and won’t grow hairs. At this point, you can start trying to distinguish the sex of your cannabis plant:

  • Look 3-5 nodes up the stem (about halfway up).
  • Study the tiny buds growing at the nodes.
  • Female: look for 2 thin hairs (stigmas), growing out of a slightly open tear-dropped bulb (bract).
  • Male: look for 2-3 pollen sacs, resembling balls and surrounded by flowers (males will not grow stigmas).

Female cannabis plant

Male cannabis plant

As time passes, visible changes to your plant will be observed, though some strains can take longer to develop than others. If you’re unsure when sexing your cannabis plant – take a step back and wait one more week. By 8 – 10 weeks after germination (outdoors) the flowering stage should be well underway and sex should be obvious.

Now and again, plants will present with both male and female flowers and are known as hermaphrodites. This can occur for two reasons: genetic predisposition or environmental stress to the plant during the flowering stage. It’s most likely to happen towards the end of the flowering period, so do keep a close eye on your plants. Like males, you’ll want to keep hermaphrodites separate from your female plants, to prevent pollination.

You can lower the risk of hermaphroditism occurring by choosing a feminized autoflowering strain.

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When to induce flowering, and when to sex cannabis plants

At around 6 – 8 weeks old, cannabis is ready to transition into the flowering stage. Flowering is induced when the light schedule follows 12 hours of sunlight and 12 hours of (uninterrupted) darkness. Indoor and outdoor plants follow the same basic light schedule, unless they are autoflowering.

Pre-flowering buds can be observed under a magnifying glass within the first ten days of adjusting the light schedule. At this stage experienced growers may begin to detect plant sex, but don’t worry if you’re not sure, just wait a little longer.

Flowering cannabis while growing outside

Towards the end of summer, the hours of sunlight in a day begin to decrease, and the amount of darkness your plant is exposed to will increase. Wait until the hours of light per day reach 12 hours and ensure plants receive 12 hours in complete darkness. About 10 days after this point (usually the summer solstice in the northern hemisphere) you can start to check as above.

The choice of cannabis strain will vary depending on the climate, and the months of flowering are determined by whether you are growing in the northern or the southern hemisphere.

If you are in Northern or Eastern Europe, you are in the cool-temperate zones. This means your cultivation season typically begins late April to early May and through to the end of September. Northern summers are short and mild with usually only a single outdoor harvest per year. Indica strains tend to grow well in cooler climates.

Southern and Western Europe are in warm-temperate zones. Southern summers are typically long and sunny, and the good weather can last until late October. Ideal circumstances to cultivate late-flowering varieties like sativas.

Keeping a close watch can help you figure out what stage of flowering you are in. Before true flowering begins, there is a stage known as pre-flowering, and this is when the plants will start to display male or female characteristics. Outdoors, pre-flowering usually begins about six weeks after germination.

If you can see the 2 white ‘hairs’ (the stigmas) growing at the plant’s nodes, but no buds have developed yet, you can safely assume that the plant is female and you are about to begin the flowering stage. If you can’t see any hairs, wait another couple of weeks and keep checking every couple of days to see if they are developing, or if balls are starting to develop instead.

Flowering cannabis for growing indoors

It won’t matter where in the world you are – when growing indoors, simply adjust the timer on your lights to follow the 12/12 light schedule. This is the beauty of growing indoors, because you can easily track what stage of flowering you are in and manipulate the plant growth cycle to induce flowering.