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. Make your first ‘cross’ a success by creating a structured breeding program with these 6 tips and a simple, 4-step program.
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.
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!
6 Tips for Cannabis Breeding Success
Make your first ‘cross’ a success by creating a structured breeding program with these 6 tips and a simple, 4-step program.
Breeding programs for almost any plant can be as simple or as complex as you choose to make them. Fortunately, you can quickly and effectively develop your own breeding program, even if you are a beginner. All it takes is a sharp eye for positive traits that you’re interested in developing and an accurate record-keeping system to track the usable crosses you’ve made, as well as the parental lines (male and female) that you’ve used.
Cannabis is dioecious (meaning the species includes separate female and male plants) as opposed to monecious (which means that an individual plant can have both male and female flowers). You need both male and female plants to begin a breeding program. TIP: It is imperative that you separate males and females from the beginning, and keep them separated throughout the program to ensure that you don’t get unwanted contamination by pollen from male plants that you have not selected to cross.
So how do you select breeding parents or parental lines to begin with? While it is relatively easy to select the female line, it can be difficult to select male lines for the following reasons:
- All the traits of interest on the female selection can be seen or documented, including: growth and development rates; flower characteristics such as size, quantity, smell and color; as well as potential for accumulating THC or CBD, and terpenes. This cannot be said of male plants.
- Male plants can only express growth and development traits visually. All other bud traits are hidden in their genetic makeup and are not expressed for selection. You can select for pollen sac size and density, but the data so far is inconclusive on how these traits translate to female flower size and density.
You can easily begin by selecting known female strains that have most or all the desired traits that you want expressed in any cross, and by selecting males that are derived from strains having other or stronger vegetative traits that you want incorporated into your new strain.
An Emerald OG strain cultivated by Clade 9 . Note the yellow stigmas on the buds, which indicate readiness for pollination.
TIP: Once you’ve selected your P1, or parental lines, you must cross them by gathering mature pollen from the male flower and physically placing it onto the mature female flowers. You can tell when the female flower is ready by observing the stringy, white-yellow stigmas developing from the buds. Many people say these stigmas look like hairs. Tip: Once the stigmas are seen, you can pollinate within a two- or three-week period, so long as pistils are still present and white in color. The males are ready for pollen extraction once you see the oval-shaped anthers starting to split open and release pollen. You can also tell by observing any powdery, yellow pollen accumulating on leaves just under the male flowers.
At this point, make sure you’ve isolated both female and male plants to avoid unwanted cross-pollination and follow these steps:
Step 1. Place a piece of foil or a smooth plastic cup under the pollen sacs while you shake them. You will see the yellow powder (pollen) accumulating. A little bit of pollen goes a long way. TIP: You can break up the total amount of pollen you have collected into packets and freeze them if you intend to use the extra pollen in the future.
Step 2. Isolate the female plant you want to pollinate and either shotgun the entire plant by shaking off your pollen above the plant and letting it float down onto the stigmas, or pollinate specific flowers individually by using either a fine-tipped brush, your finger or a pen cap. Pollinating individual flowers gives the breeder the ability to pollinate the same female plant with pollen from several males at one time. If you take this approach, make sure to label each branch or flower with the specific cross.
In breeding terminology, the female plant typically goes first in the naming convention. For example, “Snake Eyes x Diamond Dust” means Snake Eyes is the female plant receiving the male Diamond Dust pollen.
Step 3. It is imperative that your pollinated female plant is isolated from all other plants while seeds are developing, unless all the female plants are receiving the same male pollen.
Step 4. Provide mother plants with a good source of nutrients, including more nitrogen than what’s included in most bloom nutrient formulas. It may be helpful to switch to a vegetative nutrient schedule to ensure seeds receive what they need during the seed-formation process. Seeds should start forming a few weeks after pollination, and will be busting out of their heavy calyxes several weeks after that. If you need to keep the seeds, save them in a cool, dark place—like a refrigerator.
You have now made your first successful cross! The seeds derived from this cross are called F1. If you continue to cross F1s with each other, the resulting generation is called the F2.
Now you can germinate your F1 seeds and see how they grow. Do they grow fast or slow? How do the buds develop? How long is the flowering stage? What is the smell like? How about the taste, or the potency?
TIP: It may be helpful to keep clones of your plants in case one happens to be a real winner. That way you can use it as part of your breeding program indefinitely.
At this point, it is important to stress record-keeping. TIP: To breed successfully, you must keep great records. Write down which plants were bred together and how their offspring performed. This lets you keep track of traits that show up in the parents and offspring. It will also help you create new strains because you’ll be able to know what traits to expect when breeding certain plants.
David Holmes has 20 years of cannabis breeding and cultivation experience. He is co-founder and CEO of Clade 9 . Dr. William Torello has over 35 years’ experience in the plant and soil sciences. He works for Clade 9 out of Los Angeles.