Cannabis Flowering Stage: A Week by Week Guide

The cannabis flowering stage is the most important and exciting part of any grow. Know what to expect during flowering, common issues your plants can face, and some important growth tips for this critical period.

Several things take place during the cannabis flowering stage, but most importantly, your plant begins producing big, beautiful buds. During this time, the plant will undergo several changes in appearance and growth habits.

By understanding what to expect during each week of flowering, growers can better care for their plants and produce a high-quality harvest. Here is a week-by-week guide to the cannabis flowering stage. You will learn what to do and how to do it to guarantee the best bud quality and maximum yields for your harvest.

What is the Cannabis Flowering Stage?

The flowering stage of a cannabis plant is when the plant begins to produce flowers (buds). The flowers are the plant’s reproductive organs and contain the male and female reproductive cells.

The male flowers produce pollen which is used to fertilize the female flowers. The female flowers produce the seeds, which will grow into new plants. Unpollinated females produce buds instead of seeds.

The length of the flowering stage depends on the strain of cannabis being grown, but it typically lasts 8-10 weeks.

The flowering stage is when the plant produces cannabinoids and terpenes, which provide the beneficial effects associated with cannabis.

When Do You Start Flowering a Weed Plant?

One of the most crucial elements in ensuring the success of your plants is knowing when to switch your plants from the vegetative stage to the flowering stage. You will decrease the final yield if you switch too soon.

You can move on to the flowering stage once the plant has developed a robust root system. Start the flowering stage after careful consideration of numerous factors such as:

• The maximum size the plant can achieve within your setup
• The type of strain(s) being grown
• The source of the plant (from seed or clone)
• The grow method being used

When making the switch, you must be mindful of these factors and how they may affect the final harvest. Be cautious while adopting the strategies and procedures others utilize because every grow is different.

The plants can double in size after switching to flower so most growers switch when the tent canopy is half full or after 8 weeks of veg, whichever comes first.

I typically switch to flower in week 9 when growing 4 photoperiod strains in a 4×4 tent. This allows for 2 weeks of the seedling stage and 7 weeks of the vegetative stage. I used to veg for the full 8 weeks, but was always getting closer to the lights than desired, even with scrogging and other low-stress training.

How to Start the Cannabis Flowering Stage

The cannabis flowering stage for photoperiod/feminized strains is initiated by changing the light schedule from 18 hours on and 6 hours off to 12 hours on and 12 hours off. When the plant experiences 12 hours of continuous darkness, it will begin the flowering stage.

Autoflowers do not require a change in light schedule. They should be kept at 18 hours on and 6 hours off for the entire grow. As the name suggests, autoflowers automatically transition to the flowering stage on their own. This is typically between weeks 3 and 5 from seed.

Week 1 of the Flowering Stage for Cannabis

The plant begins slowly transitioning to flowering. Most changes are happening internally at this point and are not visible.

The bud spots that began showing during the late vegetative stage, will become larger and more bud spots will gradually appear.

The plant will continue to grow during the first few weeks of flowering. This is often referred to as the stretch period. Continue to train the plants while they’re still growing. This could involve tucking branches if using a scrog or trellis net, or tying down branches as necessary. Topping should never be done after the flowering stage has begun.

I recommend continuing with the vegetative stage nutrients during the first two weeks of flowering as the plant is still using quite a bit of nitrogen at this point. If you’re using a nutrient system like the FloraSeries, then follow their transition dosing.

Week 2 of the Flowering Stage for Cannabis

You may notice the first white pistils forming on your cannabis plants during the second week of flowering. These little hairs are what will eventually develop into buds. Your cannabis plant gradually shifts its focus from developing roots, leaves, and stems to developing flowers.

Keep in mind that the buds will start to become more fragrant at this point, so take precautions if necessary. Also, the likelihood of mold increases substantially during the flowering stage so monitor closely.

The plant is likely still using quite a bit of nitrogen so either mix the vegetative and flowering nutrients together during this week at half strength or stick with the vegetative nutrients for one last week.

I always defoliate and lollipop each plant after the second week of flowering. This is the second major defoliation. The first is done 2 weeks prior to switching to flower.

Lollipopping is a low stress training technique that involves trimming the bottom 1/3 of the plant. Remove all the small stems that are unlikely to reach the top of the canopy. These won’t receive enough light to produce quality buds so it’s better to just remove and allow the plant to focus it’s energy on producing bigger top buds.

Week 3 of the Flowering Stage for Cannabis

Your cannabis plants will continue to decrease their upward growth and will eventually come to a complete stop. The plant begins focusing all its energy on developing buds.

You may now see the first indications of actual buds beginning to form in the areas on the plant where you had previously seen some white hairs/pistils. They’ll likely still just look like balls of white hair though.

Begin giving only flowering nutrients by this point. I recommend starting at half the recommended dose. Keep an eye out for nutrient deficiencies or nutrient burn and adjust accordingly.

Week 4 of the Flowering Stage for Cannabis

Your cannabis plants likely stopped growing altogether and are concentrating all their energy on developing buds by week four of the flowering period. White hairs will still protrude from the buds, but the buds themselves will get bigger and fatter every day. Your plants will now create more trichomes as more and larger buds develop, increasing the odor’s intensity.

You won’t have to focus on training your plants any longer because they will have ceased growing. For the branches that you previously tied down, you may now consider holding them up if they need structural support.

Week 5 of the Flowering Stage for Cannabis

You should see substantial thickening of the buds during the fifth week of flowering. Be sure to monitor the humidity in your grow area as the chance of mold increases with each week of flowering. A relative humidity of around 40% is ideal during this period.

Your plant will now emit an exceedingly potent odor. If you grow indoors, be sure your exhaust fan and carbon filter are functioning correctly. If odor is a concern, consider adding an intake fan to the bottom of the tent and closing off the passive vents to prevent odor leaking.

Your plants will be producing trichomes rapidly at this point and they’ll appear clear or translucent when observing with a magnifying glass.

Week 6 of the Flowering Stage for Cannabis

At week 6, buds will keep expanding and moving closer to maturity. Common issues during this time include bud rot, which can be prevented by good airflow and low humidity. Keep an eye on the buds for signs of rot. If you see any, remove the buds immediately.

Monitor the plant closely and ensure it is getting enough nutrients and water. Be sure to also keep an eye out for pests and diseases. You may need to treat the plant with insecticides or fungicides if problems arise.

The pistils will begin darkening and flattening if they haven’t already to an orange or amber color. The trichomes will continue to transition from clear to milky white.

Leaves will likely begin gradually yellowing during weeks 6 and 7 regardless of nutrient deficiencies. This is perfectly normal as harvest approaches.

Week 7 of the Flowering Stage for Cannabis

The theme of week seven is patience. There isn’t much change, but the buds keep getting fatter. The pistils will continue to darken and the trichomes will transition gradually from white to an amber color.

If not already, you will almost certainly see leaves turning yellow this close to harvest. Depending on the strain, you may also see the leaves turn to other colors as well.

In week 7, I typically stop feeding and begin flushing the plants with water only to remove any excess nutrients that have built up in the growing medium. The plants will utilize most of their accumulated nutrients between flushing and harvesting, producing sweeter and more fragrant buds. If you don’t flush, the buds won’t taste or smell as good and will be harsher on your throat when smoking.

Week 8+ of the Flowering Stage for Cannabis

At this stage in the flowering process, the buds will be fully developed, and the plant will be preparing itself for harvest. You also get to see the maximum color expression of the plant. The buds should be large and dense, and the leaves will continue to yellow and turn other shades. In general, the final weeks of flowering are when marijuana plants gain most of their weight.

At this time, the plant may be ready for harvesting depending on the flavors and effects desired. I typically give it an extra week and harvest after week 9 for the majority of strains.

When to Harvest?

Cannabis plants can be harvested based on the color of their trichomes. The plant is not yet ready to harvest if the trichomes are clear. If the trichomes are all white, the plant can be harvested, but it will be less potent. If the trichomes are all amber, the plant is past its peak and may be starting to degrade.

Thus, the best time to harvest cannabis is when the trichomes are an even mix of white and amber. If mostly white, the bud will give a more energetic effect. If mostly amber, the bud will give a more sedative effect.

To check the trichome color, use cell phone camera or magnifying glass to look at the trichomes on top of the buds.

Summary

The cannabis flowering stage is the last stage of growth before harvest. This is the stage when flowers (buds) form on the plant.

The flowering stage is initiated for photoperiod/feminized plants by changing the light schedule from 18/6 to 12/12. Autoflowers automatically transition in weeks 3-5 to the flowering stage without changing the light schedule.

Switch to flowering when the tent canopy is half full or after 8 weeks of veg, whichever comes first. The plant will gradually stop growing vertically and focus all of it’s energy on producing buds.

Monitor for nutrient deficiencies and mold thoughout the flowering stage and harvest once the trichomes are a mix of white and amber when observing with a magnifying glass. This is typically after 8-10 weeks of flowering.

For information about the ideal harvest time, check out When to Harvest Cannabis.