The flowering cycle of cannabis plants

The flowering cycle of cannabis plants

The flowering phase is one of the most exciting times for cannabis growers. After all, it's here when your plants start producing their long-awaited buds.

Given the significance of this stage of the growing process, it’s extra important you understand both your plants’ flowering and pre-flowering cycles and how to get the most out of them at this time.

Without going into too much detail, the pre-flowering phase is a stage of the cannabis grow cycle just before flowering. This cycle usually happens during week 4 of the vegetative phase and is when you’ll begin to see the distinct male or female characteristics of your plants.


The flowering cycle takes place after the vegetative phase and is when cannabis plants begin to produce flowers. The duration of this cycle varies depending on the genetics of your plant.

For most indica and indica-dominant strains the entire cycle usually lasts between 7-9 weeks.

Sativas and sativa-dominant strains, however, can take over 10 weeks or more to reach maturity. Extremely Sativa dominant strains are known to flower as long as 16 weeks!

Remember that plants begin flowering when they receive less light per day. In an indoor environment, this happens when you bring your light cycle down from 18-6 to 12-12 hours of light/darkness per day. Usually this is after 1-4 weeks of vegetative growth

Outdoors, however, this happens naturally when the days become shorter, which usually happens during fall or the end of summer.


Here is a basic overview of the average flowering cycle of a cannabis plant. Remember, how your plants flower depends on their genetics and this is just a rough guide designed to give you a basic idea of what to expect.

  • Week 1: The earliest signs of flowering are characterized by slower growth.
  • Week 2: By this time, you’ll begin to notice small flowers forming at the nodes of your plants.
  • Week 3: By this stage, the plant does its last growing, usually getting about 25-50% larger than what it was in week 1.
  • Week 4: By week 4, the vegetative growth of most plants has come to an end. From here on out, your plants are going to be focused on producing frosty, tasty, and potent buds for harvest.
  • Week 5: At this stage you’ll notice fast growth of your flowers Those that sprouted earlier will be growing thicker while new flowers will also be sprouting in other previously bare areas of the plant.
  • Week 6: Some fast flowering cannabis varieties may be ready to harvest by this time. However, others will still need time before maturing. You’ll notice your buds swelling, especially the calyxes, and you’ll also find your plants developing a relatively intense odor.
  • Week 7: By week 7 most of your calyxes should be ready to burst and produce resin, that is also the moment you may see signs of incoming maturity of your flowers Some earlier buds may already have well-developed pistils by this stage.
  • Week 8: Most strains with an average 7-8 week flowering cycle will be at their peak by the last 2 days of this week. Your pistils should be a deep orange or red color and your buds should be coated with a thick, resinous layer of trichomes. If not harvested by this stage, the potency and quality of the buds will begin to deteriorate.

Note: If you’re working with a strain with a long flowering period, this cycle will be the same but the developments will just happen more slowly. Either way, pay special attention to your plants and how they develop so you harvest them just at the right time.


In order to induce and maintain the flowering cycle of your plants you’ll want to expose them to a constant 12-12 light cycle. This means they get 12 hours of light and 12 hours of dark day in, day out.

For best results, you’ll want to use a HID light that falls somewhere along the yellow or red color band. Using this kind of light will ensure your plants get just the right amount of high-quality light which will maximize their potential.

If you’re growing outdoors you obviously won’t have this much control. Hence, just make sure your plants are in an area where they can get as much exposure to regular sunlight as possible. Also, make sure they are positioned so the light reaches all parts of the plant evenly.


Cannabis typically needs nitrogen, potassium, and phosphorus to grow efficiently. During the flowering cycle, you’ll want to make sure your nutrients are particularly rich in the latter 2 (potassium and phosphorous) as these are the key nutrients the plants use in the production of buds.

Be careful with nitrogen fertilizers, especially after 4th week of flowering. Excess nitrogen can lower plants resistance which attracts pests and diseases.

You might want to consider thoughtful use of "CaMg" additives which are known to improve general performance of plants, especially in the flowering stage. Remember to lower the doses and stop adding fertilizers around 2-3 weeks before the harvest in order to let the plants reach the finish line without any excess nutrients in the plant system or growing medium.


The most important part of growing cannabis is paying careful attention to your plants. While they may not actually speak, cannabis plants are very good at giving you signs about what they need and how they’re developing. Hence, make sure to read up on grow literature and pay special attention to the unique genetics and phenotype you’re working with.

In doing so, you can rest assured that your plants will be the best they can be and you’ll be rewarded with a heavy harvest of delicious buds.