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Cannabis Flowering Week By Week

Cannabis Flowering Week by Week

The Cannabis Flowering: Week by Week

Welcome to Annibale Seedshop’s informative blog! In the past few articles we have studied the various stages that Marijuana plant must go through before reaching Cannabis Harvest. We have analyzed how the Cannabis Germination Stage is as important as the Cannabis Vegetative stage. We then saw specifically how the Flowering stage is composed, dividing it into two different moments. Today we will take a closer look at what needs cannabis requires in each week of flowering!

Start of Cannabis Flowering Stage

As we saw in the last chapter, the flowering of the Cannabis plant is divided into two phases with precise different needs. The first flowering phase lasts on average the first 4-6 weeks, where in this phase there will be the need for a still high nitrogen supply. In fact, Cannabis will not stop requiring it until its growth is completely interrupted, with a consequent need for Phosphorus and Potassium. If your plants haven’t stopped growing yet, don’t stop feeding nitrogen.

Having nutrition problems in the first few weeks of flowering could lead to future nutritional imbalances, resulting in deficiencies or over-fertilization.

Remember that if you have changed the hours of light to switch to flowering and your plants are too tall, you can opt to change the lamp on the 21st-25th day of flowering, continuing to keep a 6400 ° K spectrum white light. This trick will help keep your plants lower during the stretching period. See more about first stage of Cannabis flowering in this article!

flowering stage of cannabis plants, week by week

1 & 2 Weeks of Cannabis Flowering

After changing the light cycle of the plants, no big sudden change is to be expected. In fact, the Cannabis plant must have time to acknowledge that the summer is over. One of the most common mistakes in this period is to stop giving the vegetative fertilizer. Although the plants have actually moved into the flowering phase, their nutritional needs will not change suddenly.

In these first two weeks, therefore, do not expect to see flowering tops, you will have to settle for the first flowers. The “Pre-flowers” are, in fact, the first flowers to emerge from cannabis plants to establish their sex, they can be found in the space that intersects between the stem and the stage of leaves. Usually, you should be able to see these precious flowers between the seventh and fifteenth day after the lights change.

Many growers consider the time of pre-flower appearance to be the first day of flowering.

3, 4 & 5 Weeks of Cannabis Flowering

After spending the first two weeks growing slightly, you should now see them stretch under the effect of “Stretching”! At this stage, cannabis plants can grow to five times their height, growing to over 2 inches per day.

Care should be taken with respect to the covered heights and the available spaces: overcrowding is also possible for plants!

Do particular attention to the exact nutrition to administrate to the plants. Plants at this stage will have a strong need for nitrogen to quickly create their cell tissues, but will stop their need immediately after stretching. Therefore, slow-release nitrogen should not be given as being with too much nitrogen at a very advanced stage of flowering would completely compromise the final quality of the flowers.

In these weeks you will see how the plants begin to throw new buds into new branches. If you are already observing a rapid development of the flowers, you can drastically decrease the use of nitrogen (but not completely), and improve the supply of phosphorus, potassium and microelements (such as Calcium, Iron, Magnesium and Sulfur, essential for the formation of trichomes).

Last Stage of Cannabis Flowering

At the point where you can see numerous pistils forming throughout the top of your cannabis plant, you have reached the second and final stage of flowering. The exact week to consider will greatly depend on the genetic characteristics of your strain. A Cannabis Strain Indicates that Skunk # 1 will certainly have entered the final flowering phase by the end of the 5th week of the lights change (Day 35). On the other hand, for a dominant Sativa like Amnesia Haze, you will have to wait for the 7th week.

The environmental factor will also depend, since Marijuana plants grown outdoors will be much slower than those grown indoors. This is because the hours of light indoors in flowering are usually 12, outdoors they are about 14. This will mean slower and more abundant flowering outdoors, and faster (but less productive) flowering indoors.

A very useful advice at this stage is to nebulize Neem oil for the last time, in order to prevent an infestation or a sore when it is no longer possible to intervene with specific products in order not to ruin the taste, aroma and quality of the flowers of Marijuana. Read more about last stage of Cannabis flowering in this article!

cannabis flowering week by week fist stage

6 & 7 Weeks of Cannabis Flowering

Ladies and gentlemen, get ready and fasten your seat belts because here we come to the best and most satisfying part for a Marijuana grower. In these weeks it will be possible to observe, day after day, the flowers swell and cover themselves with intoxicating resin.

While it might attract the idea of cutting a few small buds and drying them out in order to try them, knowing how to wait for the best time to harvest will soon pay off the most patient and attentive of growers.

In these weeks it will be essential to subminister high doses of Phosphorus and Potassium, eliminating the presence of Nitrogen. A PK 12-13 from the best brands will be for you!

It will be important to keep the ambient temperature of your growbox below 31 ° C (preferably 28 ° C). High temperatures could degrade active ingredients and essential oils, with a weed as a result!

8,9 & 10 Weeks of Cannabis Flowering

The final weeks of flowering have arrived!

If you need, connect now the filters to activated carbon as the smell of Marijuana will be very intense. Increase internal ventilation and lower temperature and humidity to textbook levels (26 ° C / 40% Humidity).

To drive the growth of new trichomes crazy, use lamps with high doses of UV-B in conjunction with low humidity. Thinking that the plant is close to cutting, start irrigating with only demineralized water (or tap). On the otherside, if you believe that flowering is still long, continue with PK 12-13 only.

Taking photos of the plants in these weeks to see the trichomes zoomed in might be a great solution! If you think the plant has come to an end, do not water for 3-4 days before cutting. The soil will have to dry completely, but the leaves still stand up.

cannabis flowering week by week

Over 10 Weeks

Beyond ten weeks of flowering, only predominant (or pure) sativas may be present in your garden. Same rule applies to them as in the previous step: lower humidity and temperatures to achieve the desired optimal results!

In the last few weeks prior to cutting, you can cut all the sundeck leaves, so as to have a greater penetration of light into the lower parts of the plant, where usually the buds will be small and of poor quality.

Slightly stressing the plants with the defoliation technique can lead to cannabis plants producing more trichomes!

You will need to pay close attention to plants with long flowering in their final weeks. With the arrival of autumn / winter, the possibility of the plant developing mold like Botrytis can be very high.

cannabis flowering week by week harvest


Coming to the conclusion of this chapter, we can therefore say that, whether it is the seventh or twelfth week of flowering that you are in, there are particular rules and cautions to pay attention to.

The subministration of demineralized water in this phase will improve the quality of the final product. avoiding to give nitrogen from the first day of flowering will be a mistake that will lead to consequences in the future a potential remedy, Administering too much will ruin the final of the flowers, also being able to slow down the development of the plants, or in the worst case, kill them.

Beware of high humidity in the last weeks of Marijuana flowering – molds could ruin months of hard work!

Be patient as much as you can, even when the flowers seem ready. From personal experience, the desire to try flowers can play more than a bad joke!

Live or harvest, avoid handling the flowers too much. The trichomes are very delicate, and even just a slight pressure can break them, affecting the terpenes and active ingredients.

cannabis flowering week by week trichomes

That’s it about Cannabis Flowering week by week, hoping it may have let you find out more about each week of the cannabis bloom. Read our next article on “Cannabis Drying and Cure” and stay tuned!

See you soon, greetings from Annibale seedshop Team!


Davide, CEO, Founder and Geneticist