Cannabis has a number of different stages. The vegetative stage is when cannabis grows leaves and branches to be ready to support and develop the flowers. Like Learn how to find tiny pre-flowers at the base of each leaf to determine the sex of your plant in the vegetative stage (at only 3-6 weeks from germination)! An easy-to-follow guide on the best conditions for cannabis seedlings. Optimise your grow environment with use of a propagator, light, and a household fan.
Understanding The Vegetative Stage Of Cannabis
The vegetative phase of cannabis is when the plant grows and gathers its strengths to support buds when flowering.
- 1. Seedling phase
- 2. Vegetative phase
- 3. And what about autoflowers?
- 4. In conclusion
Cannabis has a number of different stages. The vegetative stage is when cannabis grows leaves and branches to be ready to support and develop the flowers. Like all other plants, has a number of different stages. Cannabis goes through the vegetative and flowering stage before it is ready to be harvested. This article will be dedicated to understanding the vegetative stage of cannabis. We can consider the start of the vegetative stage as soon as the first true leaves appear on our seedling. The amount of nutrients, light, and water your cannabis plant needs will have to be adjusted almost every week since you see the first true leaves until the end of your plant’s life cycle.
1. Seedling Phase
Even though the seedling stage is not considered a part of the vegetative stage, the vegetative stage starts when our seedling starts growing the first true leaves. After germinating and planting your cannabis seed, you will see two small circular leaves growing, these leaves are named Cotyledons and are responsible for feeding the young plant until it is ready to enter the vegetative stage.
The start of the vegetative stage can be considered as soon as the first Cotyledons (first two small circular leaves) appear on your seedling.
The seedling will take a couple of days to completely emerges from the soil and after up to 2 or 3 weeks you will see the first true leaves. Trues leaves are “fingered” leaves, the typical cannabis leaves. Once you see the first fingered leaves, your plant has entered the vegetative stage.
2. Vegetative Phase
After those first true leaves appear, your plant is officially in the vegetative stage. Although this can seem like not a big deal for us, for the cannabis plant it is a huge one.
This means the plant successfully survived the seedling stage and is now using its leaves and sunlight to photosynthesize, and is where growth really thrives. In this stage, your cannabis plant will need a little bit more nutrients (especially Nitrogen) and more water week by week. This along with the help of an 18/6 light cycle it will allow her to start producing sugars and promote growth.
The environment in your growing space should be adjusted for this stage also. You should start at around 60-70% humidity when you see the first true leaves, ending up at around 50% before the pre-flowering stage. The temperature has to be adjusted also and should be between 20-25 Celsius to provide an optimal growing environment for your plant.
If you can provide these conditions, you will see a new pair of fan leaves growing every day, and that is when you can see characteristics of the strain’s lineage. Indicas tend to be short and bushy while Sativas grow tall and with the fan leaves more scattered throughout the plant. When they have grown a little bit and have around 4 or 5 nodes, they’re quite strong, and that is when we can start performing LST techniques. This is because they had time to develop their branches and stem and are not as fragile as they used to be when they were starting to grow the first leaves.
Always be careful not to give your plants too much water or nutrients throughout all your plant’s life cycle but especially during the first weeks of the vegetative stage. Even though their structure is sturdier they are still sensitive. Watering too much, or giving your plant too many nutrients while she’s young can cause her to suffer from nutrient burn and slower growth from overwatering.
By providing a good combination of light, nutrients, humidity, and temperature, you will fulfill your plant’s needs and guarantee a good development of your cannabis plant. This means she will grow healthy, with a good amount of foliage and a strong root system. These are key elements that your plant needs in other to become tough and be ready for supporting the weight of the buds when it’s flowering.
3. And What About Autoflowers?
Autoflowers don’t depend on the light cycle to grow or flower. Unlike photoperiods that grow under an 18/6 light cycle, autoflowering cannabis strains grow from seed to harvest under the same light cycle, either 18/6, 20/4, or 24/0. This happens because autoflowers contain Ruderalis’ genetics which gives them the autoflower characteristic. But does this mean autoflowers don’t have a vegetative stage? The answer is: No.
Despite not depending on a certain amount of light/darkness to do so, autoflowering cannabis plants go through the same stages as every other cannabis plant, they are the seedling, vegetative and flowering stages, the only difference being that instead of transitioning from the vegetative stage to the flowering stage based on the amount of light/darkness, autoflowers will do so based on their age, which basically means they will start flowering as soon as they’re mature enough to do so. This is why you cannot extend the vegetative or flowering stage of autoflowers like you would do with photoperiodic cannabis strains.
4. In Conclusion
When in the seedling stage, our baby plant it’s still has a nutrient stock in the cotyledons. But after that stock ends and it starts growing the true leaves, it will need new sources of food, that’s where you come in. You have to provide the right amount of food and be really careful about what you feed them and the amount. Even though their structure is becoming sturdier, they’re still sensitive to overwatering and overfeeding. Everything that happens to your plant will have an influence on the final result and especially in how it develops in the next stage, which is the flowering stage. Remember, if we provide an optimal environment, our plant will grow big and healthy, but if we encounter any problems, our plants will have to recover from the shock and that can take a couple of days. The time she takes to recover can result in a smaller plant and can affect the amount and quality of our harvest. So be sure to keep your plans healthy and happy!
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…
(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
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 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 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.
Seedling Stage: The Best Conditions for Cannabis Seedlings
In nature, cannabis plants are typically found in warm, sunny, and humid conditions with a light breeze to grow strong, resilient stems. Mimic those conditions using a propagator, a light, and a household fan, and set your seedlings up for success!
The seedling stage of cannabis plants begins when the first two rounded leaves unfurl, and lasts for 2 – 3 weeks. By this time, the seedlings will have grown their first few pairs of serrated leaves, which usually have up to five fingers. Once this has happened, the vegetation stage begins, but for now, here are the best conditions for cannabis seedlings.
When should cannabis seedlings be exposed to light?
Seedlings need exposure to light right after the sprout breaks the surface of the grow medium. This is because the first leaves you see (cotyledons) are photosynthetic, meaning they are fully capable of capturing light and converting it into energy used for plant growth. Ideal light exposure and temperature will vary between strains depending on their intended grow climate.
Outdoor seedlings and light exposure
- To begin, keep young seedlings inside to protect them from the elements.
- Find a sunny window and place your seedlings in direct sunlight for at least 6-8 hours for the next 10 – 14 days.
- Gradually increase the photoperiod by an hour a day – working up to the 18/6 cycle.
Indoor seedlings and light exposure
- Expose to light source once seedlings emerge from the soil.
- Use a blue-light spectrum for optimal results.
- Follow the 18/6 light cycle for the next 2-3 weeks.
- Keep seedings at a safe distance from the light source to avoid heat stress.
When can seedlings be put under lights or in the sun?
What is the best temperature for cannabis seedlings?
Your seedlings will need to be kept within strict temperature settings to ensure they grow strong stems and healthy leaves. Keep your seedlings in a warm and bright place, like a windowsill where they can get plenty of sunlight. Indoor grow temperatures are set with the use of artificial light (HID lamp, fluorescent, or LED). Keep the daytime temperature to a constant 22-25°C (70-75°F). At night, keep the conditions cooler at around 18°C (65°F).
If temperatures are too hot or seedlings are too close to the light, they can burn and chances of survival are remarkably lowered.
Safe distances for seedlings from different light sources:
- HID lighting (metal halide lamp): 50 cm from the bulb
- Compact fluorescent lamp: 15 cm
- Fluorescent tubes: a few centimetres
- LED Lights: 30 cm
Set your light schedule for 18 hours of sunlight and 6 hours of darkness with a blue light spectrum. This is what is commonly referred to as the 18/6 light cycle. Light intensity can be increased when 2-3 sets of healthy, green, serrated leaves have grown. That’s when seedlings enter the vegetative stage.
Intensity dimming LEDs are optimal as they provide a spectrum of light for every stage of growth.
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What is the best humidity for cannabis seedlings?
High humidity will ensure young and fragile seedlings won’t grow tired and thirsty. They use the moisture in the air to easily feed their tiny root systems. Humidity can be managed with the use of a propagator and keeping a spray bottle nearby. The ideal relative humidity (RH) for seedlings is 65 -80% RH.
How to use a propagator
A propagator is an essential item in your grower tool kit. It’s the perfect place to keep young seedlings because it offers protection and makes it easy to hold moisture in the substrate, keep in humidity, and allow for light exposure. DIY propagators are an inexpensive option, and can be made using items around the house such as plastic bottles, egg cartons, and yogurt containers.
- Place your cannabis seedlings on a flat plastic tray with a translucent cover on top.
- Poke a few holes to allow for air flow.
- Check on your seedlings regularly to ensure they haven’t dried out, and spray with water when necessary.
- Place propagator under the preferred light source or on the windowsill.
Using a propagator for outdoor seedlings
- Introduce your seedlings to three hours of outdoor sunlight during the sunniest time of day.
- Increase time in the sun by an hour each day (weather allowing).
- Bring back inside during the night.
- Repeat this every day, and after two weeks cannabis seedlings will be strong enough to live outdoors permanently.
- Keep your seedlings inside the propagator until they grow taller than 7 cm, or a second or third pair of serrated leaves can be seen.
Using a propagator for indoor seedlings
- Remove seedlings from your propagator once they are taller than 7 cm or 2-3 sets of serrated leaves can be observed.
- Place a very weak fan near the seedlings, blowing near the tip of the plant.
Air flow for indoor seedlings
Wild cannabis plants grow robust stems by dancing gently with the breeze. This airflow is key to good structural integrity. It also prevents mould and helps seedlings stay healthy.
- Set an oscillating household fan near the seedlings.
- Set the fan to the lowest setting.
- Direct airflow near the tip of the plant.
Best Soil for an Outdoor Cannabis Garden
How to water cannabis seedlings
During the seedling stage, as your stem grows up towards the light, the roots of a cannabis plant are growing into the soil in search of water and nutrients. Watering away from the plant base forces the roots to search for water. Fostering a minor struggle for water promotes healthy and robust growth.
- Water away from the cannabis plant base.
- Let medium dry before watering again.
Check whether your soil is dry by lightly pressing your finger 2-3 mm into the soil. Watering your seedlings is a gentle balancing act. Keep a close eye and ensure that the conditions stay moist.
Soil pH for cannabis seedlings
Cannabis plants require slightly acidic, moist, and well aerated soil to facilitate growth.
- Ideal outdoor seedling soil pH: 6.5-7
- Ideal indoor soil pH: 5.5
Pots and Containers for cannabis seedlings
A container around the size of a cup, or 250 ml, is perfect for cannabis seedlings. Once they are taller than the pot is deep, carefully transplant them to 5 litre pots, then the size of the final pot is up to you. Tip – do the final re-potting before flowering begins, to avoid stressing them.
Rockwool cubes and blocks can also be used for seedlings, and can be planted out into soil or into larger blocks as above.
For the next 14 days, pay your cannabis seedlings loads of attention. They will thank you for it. Keep your grow conditions consistent, and your plants will be healthy and ready for the vegetative stage. The foundations are set, and you have the best genetics to ensure a successful crop.
Now it’s over to you. Remember to be patient and enjoy the process. Did we miss anything out, or do you have any burning questions? Post them in the comments below. Do you have experience caring for seedlings? Drop in some tips and tricks!
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.