How to Ensure Success in the Flowering Stage

cannabis plant in flowering stage
January 07, 2021

Everything that you did from preparation to seed propagation and care during the vegetative period comes down to this – the flowering stage. For some, this is the most crucial stage.

Of course, that is not to undermine the importance of the previous phases, but this is the homestretch. During this time, you focus on bud development and making sure the plants produce the highest concentrations of cannabinoids and terpenes.

What you do is determine if your harvest is sizable and successful in terms of yield, quality, and potency.

What You Should Know About the Flowering Stage

Marijuana plants have more leeway during the vegetative stage. Should there be a pest infestation or disease, for example, there is time to address the issue and nurse them back to health. Once they start flowering, it gets a little bit more complicated.

Any problem that occurs can have consequences on the overall quality of the buds and yield. It pays, therefore, to be more vigilant and know what to expect and do.

One of the things that confuse a beginner is not knowing when the transition begins. As many veterans would confess, they once were worried about the plants not producing flowers “days” after switching to 12/12 light cycle.

They would, of course, find out that the actual “flowering” occurs a few weeks into the flowering period – after spending sleepless nights.

Be aware that, if you’re growing autoflowering seeds then the light cycle and flowering stage will be a bit different as they grow much faster and flower automatically.

How Does Marijuana Transition to the Flowering Stage?

A common perception in the cannabis community is that the plants enter the flowering stage when they notice daylight getting shorter. In reality, it is the other way around.

When the duration of continued darkness increases and reaches a threshold, they will stretch rapidly, signaling the transition. Some strains can even double up in height within two weeks.

Unlike outdoors, where the plants start flowering naturally based on the time of the year, you manually trigger them indoors. From 18/6 (18 hours on, 6 hours off), switching to a 12/12 light schedule simulates fall conditions.

Thinking that the winter season is coming, they make a final push, growing a vigorous structure with plenty of fan leaves while entering the reproductive phase.

Trivia: Some strains, such as White Widow, can double up in size. LSD Feminized is even more impressive, stretching up to 200%.

One thing you should remember is to ensure complete darkness during the dark period. Any disruption, such as light seeping through a tiny hole for only a few seconds, could delay flowering. Worse, they could even turn into hermaphrodites.

As for growing outdoors, there are circumstances in which you should intervene and induce flowering. Whatever the reason might be, you could place a blackout sheet over the plants to simulate darkness.

What Are the Stages of Flowering?

Generally, there are four stages, namely (1) pre-flowering, (2) early flowering, (3) peak flowering, and (4) late flowering or maturation stage.

Note: Even as the buds start forming, do not rush into providing bloom nutrients and boosters to avoid nutrient toxicity. Quite the opposite, providing fewer nutrients during the early stages of flowering often produces better results. If there is a sign of deficiency, gradually increase the necessary sustenance into the nutrient mixture.

Instead of treating the flowering phase as a singular period, breaking it down presents one unique advantage. You gain the ability to adapt to specific nuances, and thus provide optimal conditions to produce the best buds possible. Here is a quick rundown of what happens in the different flowering stages:

1. Pre-flowering

The growth of white pistils signifies the start of the pre-flowering stage. Providing 12 hours of uninterrupted darkness simulates the fall season, triggering hormonal changes. Instead of focusing on growing mass primarily, the plants now shift to developing buds and soon – cannabinoids and terpenes.

This period is also when you pay attention to the gender of the plants.

Male plants:

  • Grow round, green pollen sacs that enlarge and do not sprout white, wispy pistil.
  • Usually are taller, have thicker stalks, greater inter-nodal spacing, and fewer fan leaves than females.

Female plants:

  • Grow pointed green calyxes that sprout two hairy, white stigmas in the internodes.
  • Usually more compact and bushy than males.

For most people, the males should be separated from the females and usually discarded. Doing so prevents accidental fertilization, thus ruining the harvest.

The general impression among beginning growers is to provide fertilizer low in nitrogen (N) but rich in phosphorus (P) and potassium (K). Doing that at this early stage is a mistake. During this time, the buds are only starting to form. They do not require more P-K than what is already provided. Furthermore, decreasing N might lead to a deficiency.

Instead of rushing, the switch should be gradual. Let the plants continue to grow more pistils and calyxes.

2. Early Flowering

For 1 to 3 weeks, the pistils and calyxes would continue growing lengthier and more substantial. They could even continue to grow plant mass, depending on the strain. Your plants are now officially in the early stages of flowering. You will also notice the buds forming into round balls with white spines.

The buds resemble round balls with white spines. At this point, continue to gradually increase P-K. And to stimulate more growth, “trick” the plants into thinking they are far along into the fall season by lowering the daytime temperature to around 74°F.

3. Peak Flowering

Your plants are in peak flowering mode when the bud sites merge to form a lengthy compilation of calyxes and white pistils. By this time, they should receive full bloom nutrients to support the further growth of the buds.

Be extra vigilant as this is the most critical stage of flowering. Any problem that arises can have dire consequences, such as under-developed buds.

Your plants, from this point forward, may no longer grow in size. They now focus their energy on bud development. You would also see trichomes forming. As the flowers grow large, they also become weighty. As such, you may have to consider supporting the stems with stalks to prevent them from snapping for carrying excessive loads.

4. Late Flowering or Maturation Stage

Once the plants reach the late stage, you see these things. Their buds look large, dense, and heavy. Some of the white pistils begin to curl and change color, turning yellowish.

Eventually, they will change into orange and then brown. As for the trichomes, you will also notice them changing from translucent to cloudy or milky upon inspection with a jeweler’s loupe or magnifying glass.

Gradually reduce the nutrients while also working on removing nitrogen from the mix. 1 to 2 weeks before harvesting, you should flush the plants to eliminate all nutrients. You do this in preparation for post-harvest processing of the buds, in which one of the things you do is remove chlorophyll and any nutrient residues.

Some of the leaves may show signs of deficiency, turning yellowish, or even falling off. That is a good sign when you are so close to harvesting already. All you have to do now is to determine the exact moment when you should do so.

What Else Do You Need to Know or Do?

There are other things you can do during the flowering stage to optimize growth, and therefore the bud’s quality and yields. Training is one, and you should do it early.


Training the plants can, for sure, enhance their cannabinoid and terpene profiles. More importantly, it can boost yields. LST (low-stress training), for example, and improve your harvest by up to 40%. And it is not a complicated process.

All it takes is bending stems to manipulate the plants into growing outward instead of upward. Doing so not only increases the bud sites. It also ensures that there is an even distribution of light.

If there is ever a time to train the plants, do it during the early stages when they are still stretching, and the stems are still soft and flexible. You cannot do that anymore once they turn woody and rigid.

Atmospheric Conditions

The conditions under which marijuana plants grow is dynamic. In other words, the optimal temperature and humidity levels are not the same for vegetative and flowering stages.

During the day cycle, keep the temperature around 65 to 80°F (18-26°C), and the dark cycle at 64-68ºF (18-20ºC). Maintaining the temp on the high side of the optimal range when the lights are on, and colder side after switching the lights off promotes the buds’ development.

It also stimulates hormones in some strains to produce purple hues. Some strains that are quite famous for that are Blueberry and Purple Thai. Granted that the colors do not translate to more THC, they do make for a striking visual appearance.

As for the humidity level, start with 40-50% during the first month of flowering. Lower it by 5% every week until it reaches 30% during the second month. Keeping the moisture level low, especially during the last two weeks before harvesting, is to avoid bud rot. Hence, if necessary, do use a dehumidifier.

Nutrients and pH

As much as you want to make sure that you are taking a conservative approach to nutrient mix and its concentration, you also want to maintain an optimal pH level. You do this to ease the plants into the new formulation suitable for the flowering stage.

At the same time, you also make sure that the roots absorb all the minerals needed to sustain growth.

How Do You Prepare for Harvesting in the Last Two Weeks?

There are two ways to know if the window to harvest the buds at its peak is coming soon. Observing the trichomes and also based on the known growth pattern of the strain. A couple of things you do is to start reducing the nutrients and flushing the plants.

A nutrient deficiency throughout the seedling, vegetative, and early to peak flowering stage can spell disaster. Not when it is this late. By now, the calyxes and pistils look swollen and reddish.

The resins continue to produce cannabinoids and terpenes. Depriving them of nutrients may seem counterproductive, but that is precisely what you should do. Even if the leaves start to turn yellowish, it no longer matters.

Flushing the medium removes nutrients. This way, the plants would resort to using up nutrients already absorbed in their system. What you want to achieve is that when you harvest the buds, there would be only trace amounts left. Unfortunately, nutrient residues cause the smoke to be harsh, which is why they have to go.

Observe the color of the trichomes. Once they turn milky, it is time to harvest. The buds would, at that point, contain the highest concentration of THC. You could wait a little more, letting the trichomes turn amber.

In this case, some of the THC would have degraded, converting to CBN. The effects, instead of highly euphoric, would not be more relaxing (or couchlocking).

The Flowering Stage Is All About the Buds and Trichomes

Your focus during the vegetative stage is for the plants to grow in size. Once the flowering period begins, then it is all about bud and trichome development. Instead of providing a set of conditions, treat this stage as four distinct phases.

This way, you can provide for their needs, ensuring each step of the way, they are growing at their best. A successful harvest is not only about getting the buds. It is more about raising quality levels and yields.