First Signs of Flowering Stage: What to Look For

Knowing if your plants are male or female is an important step in the growing process. However, it’s one that typically can’t be done until the plants have started flowering. This usually means that you have to wait at least a few weeks but it can take months depending on your grow schedule. Knowing what to look for early can save you a lot of hassle later.

Cannabis plants, broadly speaking, grow in two phases; vegetative and flowering. The vegetative stage is when the plant puts down roots and grows the framework needed to support itself while the flowering stage is when the magic happens and your plant produces those glorious sticky buds.

But the flowering stage itself can be further broken down week by week. Whether your using photoperiod or autoflowering seeds, this guide will show you what you should be looking for at each stage to make sure you get the best results.

When does cannabis start flowering?

When growing indoors, flowering starts when you switch your grow lights to a 12/12 light cycle. This refers to the practice of putting your plants under 12 hours of light and 12 hours of darkness each day. This is what signals to the plant that it’s time to start flowering as it “tricks” the plant into thinking that the seasons are changing. 

If you’re growing outdoors, the point at which your plants will start flowering varies based on the strain and your latitude.

If you’re growing autoflowering seeds, you don’t need to worry about light periods to start flowering. These plants are best served by 18-24 hours of light a day and they’ll start flowering on their own after just a few weeks and follow the same patterns as photoperiod strains.

Weeks 1-3: The first signs of flowering

During the first few weeks of flowering, your plants will experience an explosion of growth. Cannabis plants can, and frequently do, double in height after the switch to flowering. A good rule of thumb is that a plant will undergo up to 2/3s of its total growth in the flowering phase so be sure to start flowering well before you think you’ll need to.

The very first signs of flowering can appear as early as a week into the process. The earliest changes you’ll notice are the growth of white hairs known as pistils at the joints where fan leaves meet the stem (the area known as a “calyx”). These “pre-flowers” are a sign that everything is going smoothly.

Soon, you’ll start to see groups of single leaves sprouting out from the tops of your main colas and white pistils will start coming out of the middle of these. These sites will form your main buds.

This is also the point when you can tell if your plant is male or female.

Is my cannabis plant male or female?

Some new growers are surprised to learn that only female plants are useful for harvesting flowers. This is because they are the only ones that produce the flowers that you’re looking for. If it turns out that your plant is male, you’ll need to completely separate it as it can pollinate the rest of your crop leading to far lower-quality flowers. Luckily, these male plants aren’t totally useless, check out our guide on what you can do with male plants.

After a week or two, female plants will start sprouting more and more white pistils but will still take some time to grow proper buds. If a plant is male, you’ll start noticing pollen sacs that appear as small balls underneath each calyx.

Can I tell if a plant is male or female before flowering?

Yes, there is a chemical test that can be done to determine the sex of a plant as soon as one week after germination. However, this is expensive, time-consuming, and of minimal value for most growers.

Overall, the best way to make sure that your plants are female is to use feminized seeds. These typically have a 95-99% chance of being female. You’re in the right place; WeedSeedShop sells feminized seeds, to ensure you don’t ever miss a beat. We carry both photoperiod feminized seeds like White Widow and Critical Skunk, and autoflowering feminized seeds such as Cookie Kush XXL and AK 48.

Weeks 3-4: The first true flowers

The rapid growth of the first few weeks will start to slow down by week 3 or 4, but your plant will keep growing a bit longer. At this point, you’ll start seeing true flowers from wherever the pistils had been growing. These pistils at this stage should all be white and sticking almost straight out.

At this point, your plant will start spending more and more energy on growing flowers and is particularly vulnerable. Make sure that the nutrient levels you’re using are appropriate and stick to the dosage recommended on the label. 

As your plant gets pickier, be sure to keep an eye out for any potential deficiencies. These can present themselves in a range of ways including discolored leaves or stems. Also, check for signs of possible overfeeding (nutrient burn). Nutrient burn usually shows itself at the tips of leaves as they become brittle and discolored.

Week 4-6: Full flowering

After 4-6 weeks, your flowers should be getting bigger every day. They’ll still be covered in all-white pistils growing out in every direction, but the buds will just keep exploding. You should also start noticing the growth of the first trichomes (little clear crystals) all over the flowers.

At this point, your plant should have stopped growing vertically and all of its energy is going into making flowers. The aroma will begin to become stronger and may even need to start propping up some branches as they get weighed down by buds.

All that’s left to do at this point is to just keep doing what you’ve been doing. The plant is on autopilot and your job is just to keep it alive.

Weeks 7-10: The final countdown

The last few weeks are the most important for the plant and the most stressful for the grower. At this stage, there really isn’t much left to do but wait. Many novice growers become impatient and harvest too soon. Be patient, you’ll see your buds getting bigger with every passing day at this stage.

Different strains flower at different times but they’re mostly all in the 7-10 week range. During this time, you’ll need to keep a close eye on your plants to make sure that you harvest them at the right time. Check out our guide on the Best Time to Harvest Cannabis for details.

When should I flush my cannabis plant?

Flushing (or leeching) a plant is when you stop giving a plant nutrients and instead give it only water. This allows the plant to get rid of salts and minerals that it has taken in and provides a better taste in the final product. Without leeching, you risk your smoke being harsh with an unpleasant, chemical taste.

For soil growers, it’s best to flush your plants for 10-14 days before harvesting. If you’re growing hydro, you should flush your plants for 4-7 days.

Once everything is ready to go, it’s time to harvest!


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  • Author_profiles-WSS-Ken

    Kenny Hall

    Raised in the Colorado Rockies, I moved to Prague in 2017 and have never looked back. In my poorer college days, I learned all I needed to start growing my own and have kept up with the hobby on and off for nearly 20 years. When I'm not writing or tending to my garden, you'll find me in the park with a beer, a bowl, and a big bag of buds basking under a beautiful blue sky.
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