When Do Cannabis Plants Begin to Flower?

It’s flowering season for cannabis! Here’s a guide on when your plants will begin to flower based on their strain, sex, and more.

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Cannabis plants typically flower within 10-12 weeks, though the exact timing depends on the strain. indica strains tend to have a shorter flowering time than sativas. Some growers prefer to “force” their plants to flower by manipulating the light cycle, but this is not necessary.

Flowering is induced by shorter periods of light exposure (called the “light cycle” or “photoperiod”). In nature, cannabis plants begin to flower in late summer/early fall as the days grow shorter. Indoors, growers can control the light cycle and induce flowering at any time of year.

For most growers, the goal is to produce female plants that produce high levels of THC (the main psychoactive compound in cannabis). Male plants are usually discarded, as they do not produce significant levels of THC and their pollen can ruin a batch of buds. However, some growers cultivate male plants for their hemp fiber or CBD-rich pollen.

The Science of Flowering

Flowering is the process of sexual reproduction in plants. The cannabis plant produces flowers that contain high levels of cannabinoids, which are the compounds that are responsible for the plant’s psychoactive effects. The flowering process is initiated by the plant when the day length, or the amount of time the plant is exposed to light, decreases.

The Cannabis Life Cycle

Cannabis plants go through well-defined stages of development. These stages are determined by the amount of time the plants spend in each stage, and the changes that occur during each stage. The main stages in the life cycle of a cannabis plant are as follows:

Seedling: This is the stage when the plant first sprouts from its seed. The seedling stage lasts for about 2-3 weeks.

Vegetative: The vegetative stage is when the plant begins to grow leaves and stems. This is also the stage when the plant starts to develop its root system. The vegetative stage lasts for about 4-8 weeks.

Flowering: The flowering stage is when the plant produces flowers (or buds). This is also thestage when the plant starts to produce THC and CBD. The flowering stage lasts for about 6-8 weeks.

Harvest: The harvest stage is when the flowers (or buds) are collected and dried. This isalso thestage when THC and CBD levels are at their highest.

The Flowering Stage

The flowering stage is the final stage of a cannabis plant’s life cycle. It’s when the plant grows its flowers, which are the reproductive organs that contain the majority of the cannabinoids like THC and CBD. The length of time it takes for a cannabis plant to flower will depend on the strain, but it generally takes around 6-8 weeks.

The Environmental Triggers of Flowering

The flowering stage is when a cannabis plant matures and produces flowers. The flowers are where the plant’s female reproductive organs are found. When the female flowers are pollinated by the male flowers, the plant produces seeds. But before all that can happen, there are several environmental triggers that must take place in order for a cannabis plant to begin flowering.

Light Exposure

The amount of light your plant receives each day is the most critical factor in when it will begin to flower. All cannabis plants are photoperiodic, meaning they rely on light cycles to determine when to flower. In their natural environment, cannabis plants begin to flower in late summer when the days start to get shorter.

In order for a cannabis plant to flower, it needs to receive less than 12 hours of light each day. This decrease in daily light exposure triggers the plant’s flowering response. When grown indoors, you can control the amount of light your plant receives each day by using a timer to turn your lights off and on. Many growers choose to keep their lights on for 12 hours each day during the vegetative stage and then switch to an 8-hour light cycle when they want their plants to start flowering.


Temperature is the first environmental factor that initiates flowering in long-day plants. In short-day plants, temperature works in synergy with the number of darkness hours to induce flowering. A drop in temperature signals to the plant that winter is coming and that it needs to start flowering so that it can reproduce before frost kills it.


Nutrients are one of the environmental triggers that induce flowering in cannabis plants. The lack of a particular macronutrient, such as nitrogen, phosphorus, or potassium, can cause a plant to flower. However, it is more likely that an imbalance of nutrients is what causes flowering. When a cannabis plant does not have enough of a specific nutrient, it will begin to extract it from other parts of the plant, causing the plant to become imbalanced. As the plant becomes more imbalanced, it will trigger the flowering process in order to conserve energy and resources.

How to induce Flowering

Cannabis plants flower according to the light cycle they are exposed to. In nature, the length of a day changes with the seasons. In the northern hemisphere, days become shorter in the fall and winter months, and plants respond by flowering.

The 12/12 Method

The 12/12 method is the most common way to induce flowering in cannabis plants. This involves changing the light cycle from 18 hours of light to 12 hours of light, with 12 hours of darkness in between. This simulates the shorter days of fall and winter, when cannabis plants would typically begin to flower in the wild.

The Screen of Green (ScrOG) Method

The Screen of Green, or ScrOG, method is a cannabis training technique that involves using a screen to control the horizontal growth of your plants. By doing this, you’re able to create a flat canopy with an even distribution of light and buds. The result is increased yields and better quality buds.

To ScrOG your plants, you’ll need to set up a screen above your canopy. The screen should be big enough to cover the entire area where your plants will be growing. Once the screen is in place, you can start training your plants by gently bending and tucking them under the screen. As your plants grow, continue to tuck them under the screen so that they fill in the gaps.

The ScrOG method is an easy way to get evenly-distributed light and buds without having to do much work. However, it does have some drawbacks. First, it can be difficult to find a screen that’s big enough for your setup. Second, if you have tall plants, they may not be able to reach the holes in the screen, which can limit their growth.


To summarize, Cannabis plants will begin to flower when they receive 12 hours of uninterrupted darkness per day. This can happen naturally as the days get shorter in the fall, or it can be induced by the grower using a light schedule of 12 hours on and 12 hours off. Most Cannabis strains will be ready for harvest 8-10 weeks after the flowering process has begun.

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