How to sex weed seeda

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.

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.

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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!

Can You Tell if a Cannabis Seed is Male or Female?

W hen it comes to growing cannabis, sex is important. Not that kind of sex! We’re talking about the sex of the plant, and whether it is male or female. The reason for this is simple enough: only female seeds produce flower, also known as the buds you might have in your stash as we speak.

Related Articles

  • Cannabis Seeds Explained
  • What to Look for When Buying Cannabis Seeds
  • How to Germinate a Bag Seed
  • Understanding the Anatomy of a Cannabis Plant

Cannabis seeds can be male, female or hermaphrodites. Females produce the resin-secreting flower, and males make small sacs of pollen near the base of the leaves. Over the years, cultivators have learned that un-pollinated females (remember, males produce pollen) continue to make resin as they grow, and flowers that have not been pollinated are much more likely to produce high-potency cannabis. This is the basis of all modern medical and recreational cannabis cultivation, so determining the sex of a plant is highly important. But is there a way to know if a seed is female before growing?

Table of Contents:

  1. Determining if a Cannabis Seed Is Male or Female
  2. What Are Feminized Cannabis Seeds?
  3. Methods for Feminizing Cannabis Plants
  4. Separating Male and Female Cannabis Plants
  5. How Important is Your Plant’s Sex?

Determining if a Cannabis Seed Is Male or Female

The straightforward answer is that, if what you’ve got is a handful of unmarked seeds, it’s pretty much impossible to tell which ones are male or female. The only true way to tell the plant’s gender is to plant a seed, then wait for it to mature.

After a period of several weeks, the plant will begin to pre-flower, or form a small bud in the crux of a branch. One of the first signs your cannabis plant is female is the appearance of pistillates that are wispy and generally white in color. Male plants will instead produce pollen sacs that look rounded with distinct splits running lengthwise, a bit like a tiny crab claw. These are the structures that growers typically look for to determine a plant’s sex.

If you’re looking for more precise, science-based methods to tell your plant’s gender, there are several labs that can sex your plant right after germination – eliminating the lengthy (usually around 6 weeks) wait to learn its gender. Portland, Oregon start-up Phylos Bioscience is in the business of studying cannabis genetics, and they sell a “plant sex kit” that’s pretty simple to do, even for the folks that aren’t scientifically inclined. Simply press a cotyledon, or embryonic leaf, onto the kit’s filter paper and send it to their lab. They then test the leaf for the “Y” chromosome to determine its gender, just as would happen for a human male.

What Are Feminized Cannabis Seeds?

While it’s basically not possible to determine the sex of a seed from a random bag of seeds, a practice known as feminizing is quite popular. Feminized seeds are selectively bred to produce only female plants.

While the process is very effective, it’s not perfect. There’s a chance that a small fraction of the seeds produced via the feminization method will sprout hermaphrodites, which are still capable of producing pollen.

Despite the potential for ‘hermies,’ knowing your seeds are female from the beginning is probably your best bet.

There are many companies that sell feminized seeds, but buyer beware, do your research to make sure the seller is reputable, especially if purchasing online. Thanks to modern technology, most feminized seeds from reliable brands will be 100% female as advertised – but that doesn’t mean there aren’t people selling low-quality seeds out there.

Methods for Feminizing Cannabis Plants

If you have some experience growing cannabis and would like to bend a crop to your will to ensure that the seeds will be female, there are a few feminizing methods you might try. One such technique is to literally stress out a healthy female plant by interrupting the light cycle during flowering, called Rodelization Feminizing.

In the colloidal silver feminizing method, distilled water is mixed with pure silver and sprayed on female plants. This method works best when the plants are flowering. This results in pollen sacs being formed, which will allow the seeds to produce female plants.

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Feminizing via the silver thiosulfate technique involves carefully selecting a nearly mature female plant, then spraying it with a 50/50 mix of sodium thiosulfate and silver nitrate. This triggers a gender change, from female to male. Place this plant back with the others to pollinate other female plants, and female seeds are created.

Separating Male and Female Cannabis Plants

As anyone with seasonal allergies can attest, it only takes a little bit of pollen to have a big impact. The reason that growers are so intent on weeding out male cannabis plants is that a single pollinator can negate an entire potential harvest.

How? The reason is that once pollinated, cannabis plants will cease devoting energy to growing flowers and will tell the existing flowers to stop producing resin, which translates to making less buds and less THC. That energy will be devoted to producing seeds instead. Think of the plant as a battery with a set amount of power. When that supply is spent in one area, it won’t be available for another.

Now consider that a single male plant can spread its pollen to an entire room of females.

If a grow is accidentally pollinated, that means the resources that were spent to bring the plants to that stage — the water, soil, electricity, fertilizers, not to mention the price of the seeds themselves — will have been wasted growing weed that can’t be smoked.

All of those male plants will have to be carefully separated from the grow space and destroyed, or else the growers risk another disastrous accidental pollination. It takes minuscule amounts of pollen to pollinate a plant, so growers must take extensive precautions to eliminate potential contamination. In addition to helping mitigate other contaminants, this is one of the main reasons that many workers will don full-body suits when working in a grow room, ensuring that accidental pollen exposure is kept to a minimum.

How Important is Your Plant’s sex?

How much time you want to spend figuring out the sex of your cannabis plants really depends on how much time and energy you’d like to devote to growing your own marijuana. If you are a medical cannabis patient or caregiver, for example, and need to know what kind of cannabis you are getting every time to keep a reliable supply, buying feminized seeds from a trusted seller is the way to go. It may even be worth it to have your plants tested for sex before they mature. However, if you have some time, consider yourself a green thumb, and want to experiment with your grow, you could simply plant your seeds and see what comes up. Happy growing!

What are your thoughts on feminized seeds? If you’ve used them before, how did it go? Share your experiences in the comments below.

Author

Erin Hiatt is a New York City-based writer who has been covering the cannabis industry for more than six years. Her work – which has appeared in Hemp Connoisseur Magazine, PotGuide, Civilized, Vice, Freedom Leaf, MERRY JANE, Alternet, and CannaInvestor – covers a broad range of topics, including cannabis policy and law, CBD, hemp law and applications, science and technology, beauty, and psychedelics.

Erin’s work and industry insights have been featured on the podcasts The Let’s Go Eat Show, In the Know 420, and she has appeared as a featured panelist on the topic of hemp media. Erin has interviewed top industry experts such as Dr. Carl Hart, Ethan Nadelmann, Amanda Feilding, Mark A.R. Kleiman, Dr. James Fadiman, and culture icons Governor Jesse Ventura, and author Tom Robbins. You can follow her work on LinkedIn, WordPress, @erinhiatt on Twitter, and @erinisred on Instagram.

Cannabis Pre-Flowers: Identify Sex of a Plant as Early as 3 Weeks Old (with pics!)

The female plants will soon produce pistils. Wispy white hairs are a sure sign that you’re looking at female pre-flowers.

How to Determine the Sex of a Young Cannabis Plant

What are cannabis “pre-flowers?” They are little versions of adult flowers that appear on your marijuana plants relatively early in the vegetative stage.

When I first started growing weed, I learned (incorrectly) that there is no way to determine a cannabis plant’s sex until the flowering stage. But I’ve since learned that pre-flowers can reveal the plant’s sex while it’s still in the vegetative stage! Cannabis plants grow pre-flowers as young as 3-4 weeks from germination for male plants, and 4-6 weeks from germination for female plants.

Cannabis Pre-Flowers Are Small Versions of Adult Flowers. These reveal a plant’s sex.

Knowing the plant’s sex is helpful because most hobbyist cannabis growers would like to identify and remove male plants from the grow room early in the growing process. This is because only female plants make potent buds/flowers, while male cannabis plants make non-potent pollen sacs where female plants would grow buds. Additionally, female buds need to avoid pollen from male plants in order to make the highest quality cannabis (sinsemilla or “no seeds”).

Cannabis pre-flowers appear at the base of leaves when male plants are about 3-4 weeks old, and female plants are 4-6 weeks old.

Even if you’re not 100% sure about every plant from looking at the pre-flowers, it’s nice to know which plants you need to watch closely and which are definitely female. However, if precision is very important…

Chemical Leaf Tests Can Determine Sex & Potency for plants as young as 1-3 weeks

Chemical leaf testing is getting less expensive every day and can be used on cannabis seedlings with just a few sets of leaves to test for sex and future potency.

These tests only require a tiny amount of plant tissue (for example a small punch-out from a leaf, or a single cotyledon leaf), so it won’t hurt or slow down your seedlings to take a test sample!

In general, the tests are available for seedlings as young as 1-3 weeks. Sex testing uses a real-time polymerase chain reaction (qPCR) test, and potency tests use Gas Chromatography with a Flame Ionization Detector (GC/FID) or High-Pressure Liquid Chromatography with a Diode Array Detector (HPLC) for testing.

Although testing can be done as early as week 1 from germination, waiting until week 3 to conduct testing on seedlings can increase accuracy, and some companies won’t conduct testing until week 3.

There are many reasons growers would like to know plant sex as early as possible, as well as be able to estimate the overall THC/CBD ratios of future buds!

Did You Know? There are Chemical Leaf Tests that Can Definitively Determine Both Plant Sex & Future Cannabinoid Ratios of Very Young Marijuana Seedlings!

But for those of us using our eyes…

Male Pre-Flower

Female Pre-Flowers
(these turn into buds)

This female pre-flower hasn’t released a wispy white pistil quite yet

When starting with “feminized” seeds (which you can usually only get from a breeder), all your seeds should end up being female, so determining male from female isn’t very important. Learn more about buying seeds (including feminized seeds) from breeders online.

But for growers starting with “regular” (non-feminized) seeds, about half of the plants can turn out to be male. And unfortunately, there’s no way to look at a seed and be able to tell what sex it is.

Unfortunately, you can’t tell a cannabis plant’s sex for sure by looking at the seeds

How to Figure out Sex of a Cannabis Plant by Examining Pre-flowers

Vegetating plants usually reveal their sex when they’re just 3-6 weeks old from seed, but you have to know where to look.

What you’re looking for is “pre-flowers.” These are tiny versions of adult sex parts, and when you see them you can tell what sex the plant is going to be. They usually show up in the upper parts of the plant, closer to the lights, but sometimes you’ll search the whole plant and only find a pre-flower on a random branch lower down on the plant.

Vegetating cannabis plants reveal their sex with “pre-flowers” that usually appear 3-6 weeks from when the plant first germinated.

Although these are the general shapes of male and female pre-flowers, if you continue looking through the pictures below, you’ll see there’s quite a bit of variation on what pre-flowers look like from strain to strain.

Most male plants have grown a pre-flower by week 3-4 from seed, while female plants don’t show until week 4-6. Basically, all vegetative plants will have revealed their sex by about the 6th week from seed.

So, without further ado, here are pictures showing what you’re looking for when it comes to pre-flowers. Remember, pre-flowers are found at the V where stems meet a main stalk. But pre-flowers don’t usually show up all over the plant. Make sure to look around in different places, especially near the top of the plant and closer to the lights

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Note: Pre-flowers show up most often near the top of the plant and closer to the lights but could be anywhere on the plant. There may be just one on the whole plant so you may have to search all over!

Male Pre-Flowers

Male pre-flowers tend to have a “spade” shape, like the spades from a deck of playing cards. Male cannabis plants often (but not always) reveal their sex sooner than female plants.

Male pre-flowers tend to be shaped somewhat like a spade

This male plant was only 3 weeks when it made its first pre-flower. Notice how tiny it is compared to the giant-sized thumb! Often it’s unclear what the sex is when a pre-flower is this small (unless you’ve got a lot of experience) so if you’re not sure, it’s a good idea to wait and see how it develops, just in case.

Just to give you an idea how small these can be when they show up…

This is the exact same picture as above, but with the pre-flower made bigger so you can see it. Pretty tiny, isn’t it?

Male pre-flowers are basically immature pollen sacs. When the plant starts flowering, they will grow and turn into bunches that almost look like grapes.

I’ve also noticed that sometimes (though not always!) the stipules on male plants seem more “leafy” and less “pointy” than stipules on female plants (the stipules are the green hair-like growths near where pre-flowers show up). However, this is just a generality, and should be used together with other factors to determine if a plant is male! There are definitely male plants with pointy stipules and vice versa, but it’s sort of a general difference.

This particular pre-flower is really tough to determine. However, in the end, it was a male plant. The little “stem” is one clue it may be male

Just like the above male plant, sometimes you get almost what looks like two tiny little leaves that the pre-flower pollen sac “unfurls” from. In the above picture the pollen sac is still mostly hidden, while in this next picture, the tiny growths have opened up to fully reveal the pollen sac. This can be confusing because these extra growths don’t appear on all plants, and are not a pre-flower or a stipule.

Here’s another male pollen sac pre-flower that’s on a little “stem”

A single male pre-flower appears

Once you see multiple pollen sacs and no white pistils, you can be confident it’s a male plant

Although this plant ended up being male, the stipules are long, pointy and crossed as you’d normally see with a female plant. That’s why you need to confirm sex with the pre-flowers and not just look at other factors on the plant!

Sometimes the pollen sacs look a little unusual when they first start growing in, but you know it’s male when you see several pre-flowers without any pistils stacked on top of each other like bunches of grapes

If you click the following picture and zoom in close, you can see pollen sacs scattered among the leaves

This is what male pollen sacs look like when the plant actually starts flowering

This male cannabis plant has gotten further along in the flowering stage

This is what a male plant looks like at maturity when it’s starting to spill its pollen

Another example of pollen spilling onto a nearby leaf

For those who’ve never seen a male cannabis plant in its full glory

Ok, now that you know what male pre-flowers look like, what do female pre-flowers look like?

Female Pre-Flowers

Female pre-flowers tend to be longer and narrower than male pre-flowers, sometimes with a fat bottom. They also usually (but not always) have 1-2 white hairs (pistils) sticking out from the top. Sometimes it takes a few extra days for the pistils to appear.

Wispy white pistils are a sure sign that you’re looking at female pre-flowers

This pre-flower doesn’t have a pistil sticking out at first, but the shape helps tell you it’s a female plant. If you’re not sure about sex after spotting a pre-flower, it’s a good idea to wait and see for a little while, just to see if a white hair appears (which means it’s definitely a girl)

Another example of female cannabis pre-flowers that haven’t revealed their pistil yet

Here’s a picture that shows a pistil right as it’s emerging from the calyx!

If the pre-flower is very pointy and thin like this one on the right, it is often a female pre-flower

Some of the time the stipules (green hair-like growths near where pre-flowers show up) will cross each other on female plants. This certainly doesn’t always happen, as you can see from the pics of female pre-flowers on this page, but while girls can go either way, male plants rarely have stipules that cross each other. So although crossed stipules cannot be used definitively as a way to identify female plants, it can be a small clue to help guide you when you’re not sure. For example, the following female pre-flower doesn’t have a pistil, but the long thin shape combined with the crossed stipules help indicate that this plant is a girl. Whenever in doubt, wait a week and look again!

This female plant has a long, thin calyx and crossed stipules, which are typical female plant features

In this pic, you can see white pistils emerging from the calyxes. Female pistils are white and wispy, never green.

Here’s another female pre-flower that doesn’t have a white hair yet, but you can tell it’s female because it’s long and narrow, instead of spade-shaped

One last female pre-flower without a pistil yet. The long narrow shape is the only thing that gives the sex away until pistils begin to emerge

Super close-up picture of a female cannabis pre-flower

Female cannabis calyxes with pistils, under an LED grow light

Did you know that pre-flowers/calyxes/flowers are actually what holds seeds if your plant gets pollinated? Once pollen touches the white pistils, the pollen gets delivered to the inside and a seed starts forming!

Variability of Cannabis Plant Sex – How to Increase Ratio of Female Plants with Regular Seeds

In fact, to this day scientists are still not sure exactly what causes certain plants to be one sex or another after sprouting. We’ve identified several factors that predict the overall likelihood of male/female plants (for example feminized seeds always produce female plants no matter what), but sex seems to be somewhat fluid in cannabis plants when they’re first germinated.

Certain conditions such as excessive heat, stress, unusual light periods and nutrient problems can cause a greater percentage of plants to produce male flowers.

You may be able to increase the percentage of female plants with regular seeds during the first few weeks of life

On the flip side, the following factors may possibly increase the ratio of female plants with regular seeds (learn more):

  • Healthy Mom – Only grow seeds from a vigorous, healthy mother plant who never showed any signs of herming or male pollen sacs (seeds are more likely to grow pollen sacs if the mom plant had a tough start in life, or hermed during the flowering stage)
  • Cool Temperatures – Give seedlings slightly cool temperatures (65-75°F day and night) and avoid excessive heat
  • High Humidity (50-70% RH)
  • Short but not too short days. Keep consistent day and night periods with no light interruptions at night, and days should be 14-18 hours long (between 14/10 and 18/6) for the first few weeks
  • Blue light. Always start seeds under a vegetative grow light (something with plenty of blue like a Metal Halide or a 6500k CFL/T5/fluorescent)
  • Avoid Deficiencies – Make sure to provide plenty of Nitrogen and don’t let seedlings become nutrient-starved or run into other types of deficiencies
  • Prevent Stress, especially heat or light stress during the first few weeks
  • Happy Roots – Avoid over (and especially) under watering

Once a cannabis plant is about 3 weeks old, its sex is pretty much completely set and can be determined either by visual inspection or by chemical leaf test.

Unfortunately, due to the fact that different environmental conditions during the first part of life can alter the sex, you can’t look at seeds and definitively know one way or the other whether the plant will end up being female because even the plant doesn’t necessarily “know”.

For example, say you take a clone of a seedling before it’s 3 weeks old. It’s possible that one clone will be male, and the other clone will be female. However, if you take a clone after week 3, the sexes of clones will always match each other. This is further evidence to indicate that the environment can affect sex expression in some cases.