Best Practices For The Cannabis Flowering Phase

The Cannabis Flowering Phase

Luke Sholl
Luke Sholl
Last updated:

During the flowering phase, cannabis plants focus on producing precious flowers. Colas start to emerge, the plants develop trichomes and start pumping out a viscous resin filled with cannabinoids and terpenes. For most cultivators, this is the most exciting period of the growing cycle—they finally get to lay eyes on the result of their hard work!

Cannabis plants have specific demands during the flowering stage and require different levels of light and nutrients in comparison to their vegetative phase. Dialling in optimal temperature and humidity levels can also do wonders in preventing mould and boosting the quality of your flowers. Consult the guide below to learn about the stages of flowering and how to ensure that this phase is successful and leads to a fruitful harvest.

Your cannabis plants have been in the vegetative stage for a while now. They grew in size, developed a vigorous structure, and plenty of fan leaves. When the female plants grow small white pistils from the nodal areas, they’re signalling that it’s time for the flowering phase. During this phase, buds grow and develop a solid cannabinoid and terpene profile.

The 4 stages of flowering

Outdoors, the flowering phase begins naturally with the fall season, while indoor growers need to kickstart the flowering phase by changing the light cycle from 18-6 to 12-12 hours of light and darkness. Before we proceed with the details, it’s important to note that the main mistake growers make during the flowering phase is overfeeding plants. Just because buds are forming doesn’t mean that they need to be blasted with fertilisers and boosters; this often leads to nutrient toxicity. As a rule of thumb, less nutrients produces better results. If nutrient deficiency is detected, one should gradually add the necessary compounds into the mix.

1. Pre-flowering

Pre-flowering Cannabis

Usually, the flowering phase is considered a singular stage, however, there are certain nuances which are valuable to distinguish for best results. When the white pistils (hairs) begin to show in the nodal areas, the pre-flowering stage has begun. At this point, indoor growers switch the light cycle to 12-12, which signals to plants that the fall season has commenced and it's time to develop flowers. It’s important to continue with the regular veg feeding, then gradually shift it to the P-K (phosphorus and potassium) side so the buds can grow and mature.

Novice growers often switch completely from the vegetative nitrogen-rich fertilisers to P-K heavy fertilisers, which often results in disaster. At this point, the buds have barely formed, they only require trace amounts of nutrients. During the pre-flowering stage, the nodal areas will develop more pistils and larger calyxes (cannabis flowers), which leads to the next stage.

2. Early flowering

Early Flowering Cannabis

The calyxes are growing in size and the pistils are becoming longer. This is the early flowering stage. The buds resemble round balls with white spines. At this point, the plants are still growing in size and can stretch significantly depending on the strain's genetics. The buds will require slightly more P-K at this stage. If possible, the temperatures should be slightly lowered to around 23°C during the light hours. This will signal to the plants that we’re further into the fall season.

3. Peak flowering stage

The peak flowering stage begins when the bud sites merge with one another, forming a long compilation of green calyxes and white pistils. During this stage, the plants should receive higher amounts of P-K, as the buds will now grow significantly in size. This is the stage when growers need to be extremely careful with environmental conditions and feeding. If something goes wrong during the peak flowering stage, the buds won’t grow much in size. Therefore, caution is advised.

At this point, the plants will stagnate in growth, allocating most of their energy into bud formation. Large plants may need string support at this point. Buds are filled with water and can become too heavy for the stems, which might snap under the weight. At this point, trichomes are beginning to take shape and the cannabinoids and terpenes within develop.

4. Late flowering - maturation stage

Late Flowering Cannabis - Maturation Stage

Here’s the last stage in the flowering phase, the maturation stage. At this point, the buds are quite large, dense, and heavy. The white pistils are beginning to curl, turn yellow, orange, then brown. The trichomes turn from see-through clear to cloudy and milky. When left for a longer time, some trichomes will turn amber. If one desires more uplifting effects from the buds, they should be harvested when the trichomes are mostly milky. For more sedating and narcotic highs, one should wait until some trichomes become amber.

During this stage, the nutrient amounts provided should be gradually lowered and nitrogen should be virtually eliminated from the mix. 1-2 weeks before harvesting the plants, they need to be flushed of all nutrients, which are undesirable for consumption. This is usually done by drenching the soil with clear pH-regulated water. This allows the plants to utilise all the stored nutrients. After flushing the plants, the leaves will become yellow and start falling off; at this point, it’s a good sign. When the buds are fully mature, it's time for harvest, which marks the end of the flowering phase.

Watering during the flowering period


During the pre-flowering and early flowering stage, the plants don’t require additional watering. However, once the plants enter the peak flowering stage, the buds start sucking the soil dry. The buds are filled with water; it’s logical that more watering is required. The best way to go about this is to simply feel the soil. When the soil dries up, the watering schedule needs to be adjusted.

Nutrients during the flowering period

Nutrients during the vegetative phase must be nitrogen-heavy. As mentioned above, during the flowering phase, the nutrients should gradually shift to more P-K based nutrition.

Foliar feeding


Foliar feeding is straightforward during the vegetative phase, however, during the flowering phase, one wants to avoid spraying any chemicals on the buds. When the buds begin to increase in size, foliar feeding should be avoided altogether. If one needs to use foliar feeding during bloom, be sure to intelligently isolate the affected leaves from the buds. It's extremely time-consuming, but it can be done.

Best grow room circumstances for the flowering period


Light: Lighting during the flowering phase should be stronger in the "red" wavelength spectrum as opposed to "blue" wavelength spectrum during veg. The light cycle should be switched to 12-12 for indoor operations unless we’re dealing with autoflowers, which can handle longer light periods.

Temp/humidity: For photoperiodic plants, mimicking the differences between summer and fall by making the light cycle shorter and the temperatures slightly lower is good practice. Lowering the temps by 2-3°C during the flowering phase will do great, but it’s not necessary to develop high-quality buds. The humidity levels should not surpass 50%, otherwise the buds can begin to rot.

pH: For soil-grown cannabis, 6.0-6.5 pH levels are ultimate, for hydro, 5.5-6.0pH does the trick.

Ventilation/circulation: Good air circulation is important during every phase of growth. Something to consider during the flowering phase is that buds exude pungent aromas, which can be detected by neighbours quite easily.

You’re visiting our International website.