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Table of Contents

Growing Cannabis Flowering Stage of Growth

Cannabis Flowing with Calyxes

In our third and final three part cannabis growing series we will be teaching growers about the cannabis flowering stage of growth. You can read all about the first two sections of this series here, Cannabis Seedling Stage and Cannabis Vegetative Stage of growth. The flowering stage of cannabis growth is considered by many to be the most important stage of cannabis growth. In this growth stage the plant will be growing the all important buds (cannabis flowers).

When is the Cannabis Flowering Stage of Growth?

The cannabis flowering stage of growth starts once the plant grow lighting is changed to 12 hours of light per 24 hours of each day. Once the cannabis plant is large and mature enough to start flowering, growers will turn the lights back from 16 hours to 12 hours and this will start the plant to start growing flowers. These are the buds that in 8 to 14 weeks later will harvest from the cannabis plants. 

Outdoors this will happen in the northern hemisphere in mid August to Mid September. Your outdoor cannabis plants will start to grow more flowers on the upper growth of the plant. 

How long is the Cannabis Flowering Stage of Growth?

The length of the flowering stage is determined by the genetics of the cannabis plant; some strains will finish fully flowering at the end of only 7 weeks with over strains that can take many more weeks up to 16 to completely finish flowering. Most strains nowadays rarely take this long to finish flowering with most hybrid cannabis strains taking between 7 and 10 weeks to fully finish the flowering cycle of growth. 

Outdoors it is important for the grower to select cannabis strains that will finish flowering before the colder weather sets in. If the plant is not able to finish in time for harvest then it most likely will be killed by fall frosts. For example it would be very difficult for a grower to grow a cannabis plant that takes 14 weeks to flowering in Northern Canada when it starts to snow there in the middle to early October. 

It is important that the grower know the general time that the plant will finish flowering, however this is not the best way to know when to harvest cannabis as we will discuss later in the article. 

Flowering Cannabis Plant

Caring for your plant in the Cannabis Flowering Stage of Growth

Now that your cannabis plant is no longer in the vegetative stage of growth it will need different nutrients and more water to start growing the best buds that it can. First the flowering cannabis plant will no longer need as much nitrogen for flower growth. It will now need more potassium to grow larger buds. 

If you are using salt based nutrients it is time to switch to the flowering versions of the fertilizer. If using organic nutrients we recommend using a high phosphorus organic nutrient. This is best if you start using it a couple of weeks before the plant is switched to flowering lights. This will give the organic based nutrients time to start breaking down for the plant to use once flowering has started. The plant will require the most amount of potassium approximately two weeks after it starts to flower.

Warning About Nitrogen in the Cannabis Flowering Stage  

Once your plant is in the flowering stage of growth it is important not to over fertilize the plant with nitrogen. Adding too much nitrogen after the plant has started to grow flowers can actually cause the plant to start flowering much slower than it should. In some cases it can also cause the plant to not go into the flowering phase at all. 

Once the plant starts to flower it will only need a small amount of nitrogen to grow. Any extra will be pulled from the leaves of the plant, so normally there is no reason to give the plant any extra nitrogen during flowering. 

How much to water in flowering stage of growth?

Once the plant has been flowering for about 4 weeks it will not start to use more water to grow buds. Whether you are growing in hydroponics or organic you will notice the plant will start to use more water while growing. This is to help the plant grow larger flowers with more weight. It is important to make sure the plant has enough water during the flowering period of growth.

How often do you water flowering stage?

If growing cannabis in soil, let the flowering plant dry out between waterings. Once the soil in the growing container becomes dry on top it is time to give the plant a good watering. It is good to make sure that the plant is completely watered with no dry spots in the pot. 

What does the flowering stage of cannabis look like?

For the first two weeks of flowering most growers will only notice that the plant will start to stretch. This means that the plant will start to go through a period of growth where the plant will start to grow very tall in a very short amount of time. This is where plant heights before flowering are important. In the first couple of weeks your plants will almost reach up into the lights. If you do not have enough vertical space you may end up running out of space for the plant.

When stretching your flowering plants can grow almost 150% taller then they were before starting flowering. This is something you will need to keep in mind while your plants are in the vegetative stage of plant growth. Pruning Cannabis plants can also help with the plant heights before flowering. 

Cannabis Flowering Stage

Cannabis Flowering Stage Lighting 

Now that your plants are fully flowering it will be time to turn up your lighting for the biggest buds. In this period of growth, the plant will need much more light indoors than it required for vegetative growth. Outdoors your plants will flower best in the full sunlight for most of the day.  Even if your outdoor cannabis plant is in the shade for part of the day this will be fine if they are at the very least getting their sun in the main part of the afternoon. If it is very hot where you are growing, then you may actually want to move your plants (if they are in containers) out of the very hot sun. If you are looking for more in depth information on flowering cannabis we recommend this article

How long does the flowering stage of cannabis last?

This is very much dependent on the strain that you are growing or going to grow. For most indica cannabis strains, the flowering time is shorter due to the shorter natural outdoor growing season indica strains have evolved in. On the other hand, the sativa strain evolved closer to the equator and therefore had a much longer cannabis flowering stage of growth. Most growers these days will be growing hybrids of the two. This gives the grower a shorter flowering time with more cannabis sativa characteristics. 

Some strains will completely finish in 7 to 8 weeks of flowering while others can take even longer up to 16 weeks to finish completely flowering.

Should I trim fan leaves during flowering?

We recommend a technique called Defoliation where the grower will remove fan leaves that will block flowering sites of the plant. This is best completed before the plant starts to flower right up until the plant is placed in the flowering stage. However if you do see a larger fan leaf that is blocking a budding site on your cannabis plant, it is safe to remove it in the first two weeks of flowering. 

Removing too much of the plant foliage later in flowering can cause the plant to stress. This can cause the flowering plant to reverse sex in flowering, and will grow male flowering as well as female calyxes. These male flowers can pollinate your cannabis flowering creating unwanted seeds in your harvested buds. 

What are the first signs of cannabis flowering?

Depending on how long your plant will flower for as discussed above, the first sign of flowering will be the plant starting to stretch quickly upwards towards the lighting. Next growers will notice more calyxes, these are the small horn shaped flowering growing from the main growing tips of the plants. They will have two small white hairs growing from them. Calyxes will start to increase around the second week of flowering and continue to grow for about 4 to 10 weeks, depending on the approximate flowering time of your plant. 

If after 2 to 3 weeks you do not see your plants starting to stretch and growing more flowering calyxes, you may have a light leak in your flowering room. This can happen if you have some light getting into your flowering room when the lights are turned off. To see if this may be the case it is best before you place your plants in your flowering space to turn out the lights. Then wait for your eyes to adjust, if you see any light getting in from the outside of your growing space then this could be an issue. 

First Signs of Flowering Cannabis
First Signs of Flowering Cannabis

Make sure to seal off any light leaks from the inside of the room if possible. Tinfoil tape works great for blocking pin light leaks in cheap growing tents.

What Color Will my Cannabis Buds Be?

Cannabis has a few different color flowers depending on which strain you have chosen to grow. Most of the time the calyxes will start off growing green, or purple and will become even more highlighted as the weeks of flowering the plant progress. Some will even turn red or deep black in some cases. While the cannabis plant’s flower color can be changed to some extent, with colder weather, it is predetermined by the plant’s genetics. 

 What does week 3 of flower look like?

By week three of flowering, your plants should be pretty much finished stretching up towards the lights or sun. They will also be starting to grow calyxes and you will start to see lots of small white hairs (pistils) coming from your plant growing tips. 

Cannabis Flowering Weeks 3 to 5
Cannabis Flowering Weeks 3 to 5

What should my buds look like at 5 weeks?

Most cultivars of cannabis should be well into flowering at this point in time, you should also start to see some trichomes that look like small little shiny crystals growing around the flowering and leaves of the plants where the buds are forming. 

What week does cannabis flower most?

Most cannabis strains will flower the most between weeks 3 and 6, they will grow many calyxes during this time. Your plant should also start to produce lots of trichomes during this period of flowering. 

What week Do Buds Start to Fatten?

Typical cannabis buds start to swell (or fatten) in the final two to three weeks of flowering. The calyxes that have been growing now for the last 6 to 12 weeks will start to become larger and you will see more trichomes starting to grow in even greater qualities. The white pistils on the calyxes will also start to wither and die, sometimes these will be red, purple or even white depending on the cultivar that you are growing.  

Can you Flower Cannabis for too Long?

Like with any other vegetable or fruit you can flower your plants for too long. Once the plant has passed its harvesting peak it will slowly start to degrade giving the grower much less potent buds. The trichomes will start to break down, from their peak THC and CBD content. 

How to Tell when your Cannabis Buds are at Peak for Harvesting?

There is an easy and simple way to tell when your buds are at their peak and are now ready for harvesting. For this process you will need a jeweler’s loupe and a good eye. The jewelers loupe will be used for a close up look at the trichomes that are growing on your leaves and buds. At first the trichomes will be all clear when looking at them through the jewelers loupe. As harvest time gets closer for your plants the trichomes will start to appear cloudy. 

Cheap Jewelers Loupe from Walmart
Cheap Jewelers Loupe from Walmart

As the plants near peak harvesting they will start to turn amber. Some growers report that harvesting when they have more cloudy trichomes will produce a more head or “active” high good for getting things done. After the majors of the plant trichomes turn amber the buds will produce a more body high. New growers can think of this as a general “heavy” body feeling or sleepiness. 

Every grower will have their preference of when they like to harvest their cannabis buds. However we recommend harvesting when the trichomes on the buds are about 20% amber and 70% cloudy for the best bud potency. 

Outdoor Cannabis Flowering Stage

Using this method works very well for outdoor cannabis growers. When growing outdoors you can’t just “flip the lights” to 12 hours of daylight. The grower will not know the exact time that the plant started to flower in nature, only an estimate of when it started flowering. Using the jeweler’s loop will help you harvest at peak time for best results.

Dealing With Bud Rot and Mold Cannabis Flowering Stage 

One of the biggest issues that cannabis growers will face at one time or another is bud rot and mold. Once these two issues get into your buds, normally later in flowering, they can propagate and destroy your beautiful buds you work so hard to grow. Two things that growers can do to prevent bud rot in flowering is to have good air movement within and from outside the growing space and to keep their growing space as clean as possible. If you would like to read more about keeping and getting rid of bud rot and mold we recommend this great article

Cannabis Flowering Stage Bud Rot
Cannabis Flowering Stage Bud Rot

Last but not Least It’s Harvest Time for your buds!

Now that you have completed our guide to growing cannabis it is the best part of all, harvesting and curing your cannabis buds. There are many different ways that growers can go about harvesting cannabis flowers, we have a great guide here that will walk you through all the steps to get the most out of your new harvest. Remember this is one of the most important parts of the growing process even though you are no longer growing. Taking good care of your buds, and keeping them fresh for months to come. 

Final Thoughts

We hope that these guides will help new growers get started growing the best cannabis possible without making many of the mistakes that new growers tend to make when starting out. Growing cannabis is awesome, and growing top shelf cannabis is even better. If you require cannabis seeds for your next garden please don’t forget to check out the Green Avenger Seeds shop for strain selection. 

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