The Flowering Phase Of Cannabis

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Categories : Cannabis cultivation

The Flowering Phase Of Cannabis

Our beloved marijuana flourishes during the flowering phase. Here we provide you with the best practices, tips, and tricks to elevate the quality of your buds.

Once the vegetative phase comes to an end, it’s time for the buds to develop. This phase begins when the white hairs (pistils) on female plants start emerging from the nodal areas. The beginning can also be marked at the precise moment indoor growers switch the light cycle to a 12-12 schedule (12 hours of light, 12 hours of complete darkness). The flowering phase comes to an end when the buds are fully mature and harvested. During the flowering phase, the buds grow in size, which is a magical experience for growers to observe. Let’s go through the following practices to ensure amazing-quality buds by the end of flowering.


When plants display the desired shape and size, indoor growers switch the light cycle from 18-6h to 12-12h. When the plants sense the diminished period of light hours, they interpret it as “the winter is coming soon! We need to produce flowers in order to drop seeds and reproduce!” At this point, buds start forming immediately after the light cycle switch. Outdoor growers simply plant their cannabis seedlings during March-May and wait for the naturally occurring decline in sunlight hours to provide the plants with the flowering phase treatment.

Autoflowering strains don’t depend on the declining photoperiod to start forming buds; their internal flowering clock is independent of the changes in light hours. Autoflowers can handle up to 22 hours of light throughout their entire growth, from seed to harvest. Growers have different opinions as to how many hours of light autoflowers should receive for optimal results. When unsure, it’s best to stick with a 20-4h light cycle.


The number one mistake made by novice growers is over-fertilising the plants. Once they go into the flowering phase, many growers tend to stop giving the plants nitrogen and blast the soil with high phosphorus and potassium (P-K) feedings. This results in a disaster. One needs to gently approach the switch from the vegetative phase to the flowering phase. The moment the flowering phase begins, the buds are minuscule, so they require trace amounts of P-K to thrive.

Nitrogen is still necessary throughout the entire flowering phase, albeit in smaller quantities. When plants don't receive nitrogen, the leaves start to yellow and fall off. This yellowing begins from the bottom of the plant, moving its way up and preventing photosynthesis from taking place. So remember, gradually shift the feeding for optimal results. During the first stages of flowering, one should focus mostly on ensuring the leaves have a healthy green colour and stay on the plant.

The Flowering Phase Of Cannabis


Indoor growers usually use the same lights for the entire plant life cycle. HPS and LED lights are the most commonly used in indoor settings. However, if one wishes to get fancy, let’s go through some expert techniques. Many professional growers change the light spectrum depending on the cycle the plants are in. During the flowering phase, the size and quality of buds increase under lights emanating a substantial amount of “red” light, like HPS lamps. When the cannabis plants receive red light, they stretch to allow buds to grow and receive more space to catch pollen from the wind for reproductive purposes.

Something to consider is that during the flowering phase, plants can stretch significantly. In limited settings, one needs to make use of topping, ScrOG, and SOG methods during the vegetative phase if the cannabis strain is genetically prone to super-stretching, like sativa cultivars. The manipulation of the light spectrum during the flowering phase is not nearly as important as exposing the plants to the correct light cycle, and a substantial amount of light to boot. If you’re a novice grower, stick to HPS lamps. If your grow environment is very limited in space, you can use CFL lights.


During the first stages of flowering, the plants will consume virtually the same amount of water as they did during the late-vegetative phase. The water temperature should feel cool to the touch; 20°C will do. When the buds start developing larger pistils and the calyxes begin expanding in size, the roots will absorb a lot of water, which goes straight to the buds. As a rule of thumb, the bigger the buds, the more water the plants require. When growing in soil, one needs to water the plants when the soil feels mostly dry.

Many growers use the following watering schedule during the flowering phase: First day, the plants are watered with nutrients; second day, no watering; third day, the plants are watered with pure water; fourth day, no watering; repeat. It’s a good idea to switch between watering the plants with regular water and fertilised water. Different growing media will have different water retention levels, hence there is no one-size-fits-all schedule. And of course, the water needs to be pH-controlled. Between 6-7pH for soil and 5.5-6.5pH for hydro.


Indoor growers need to be slightly more careful with temperatures and humidity levels during the flowering phase in comparison with the vegetative phase. When the buds develop, they create terpenes, which generate the amazing aromas and flavours we attribute to high-quality weed.

Indoors, when the temperatures rise above 26°C, the terpenes will start disappearing from the buds, reducing their quality. Also, terpenes are there to manage the temperature levels of the plant by cooling them down. Terpenes also function as natural insect repellants. On the other side, when the temperatures drop below 15°C, the plants stagnate in growth and are more at risk of mould and various pests and diseases. During the light cycle, keeping the temperatures between 21-24°C is optimal. During the dark cycle, the temps can drop to 18-22°C. Outdoor cannabis plants can handle significant heat because the roots are suspended in cool soil. Conversely, if it's cold outside and the soil is even colder, the plants can quickly freeze to death.

The Flowering Phase Of Cannabis


During the flowering phase, especially when the buds are large in size, the humidity levels should be between 40-50% RH (relative humidity). When it gets too dry, the buds will stagnate in growth and the leaves will dry out. When the humidity levels are above 60%, however, it invites mould, especially in strains which develop dense buds. When the humidity levels are too low, one could simply purchase a humidifier, which are usually quite cheap. However, when the humidity levels are really high, one needs to get a dehumidifier, which costs loads and is a hassle for regular indoor growers. If you’re dealing with high-humidity environments, the best move is to choose sativa strains that are more stretchy and develop fluffy buds, allowing the plants to respire easily.


The flowering phase comes to an end when the majority of trichomes turn cloudy and milky. Now it’s time to prepare for the curing phase by flushing out the fertilisers and boosters from the plants. Flushing is necessary for producing quality buds. This is mainly done by giving the plants only pure water during their last 1-2 weeks before harvest. One should allow the water to drain through the soil and run out the bottom.

During the flush, fan leaves will start turning yellow and begin to fall off. Expert growers often use chemicals which attach to the nutrients and salts present in the soil, flushing them out. Both methods work, however, flushing with pure water is the best method for novice growers. The timing is key here; when plants are flushed too early, the leaves will fall off, leaving the buds immature. When the plants are flushed too late, the buds lose their potency. If one prefers a more uplifting buzz from the buds, they should be harvested when almost all trichomes are milky with some still being clear. If a more narcotic high is desired, the trichomes should be milky, with some turning amber.


There are many important things to consider during the flowering phase. The best advice for all you novice growers is to keep it gentle, don’t overdo things, and learn from your mistakes. Right now, you don’t need to think about light spectrums during your first grow. Just use HPS lamps and work your way up from there. Remember, cannabis is a weed, it grows quite robustly in natural environments. May your buds flourish!