Flowering stages in cannabis plants

The flowering stage in cannabis plants is the period when flowers and future buds begin to grow. After a few weeks of vegetative growth, the plant enters its flowering stage and our crops begin to flower.

When does the flowering stage start?

This will depend on whether we are growing outdoors, indoors or if we used autoflowering seed.

In outdoor plants, they will begin the flowering stage when the days shorten as they will receive fewer light hours.

Indoor cannabis plants enter the flowering stage with the beginning of the photoperiod and for this the lighting time should be changed to 12 hours of light/12 hours of darkness.

Autoflowering strains do not need a photoperiod change to start blooming, their vegetative stage lasts for around 4 weeks and then it changes stages automatically.

How long does the flowering stage last?

This will depend on the variety that is being grown. The flowering stage in marijuana plants generally takes 8 to 11 weeks.

The flowering period for Indica strains usually begins around week 8, but can take up to 10 weeks. Sativa varieties can take up to 10-12 weeks. Hybrid strains usually take 6 to 10 weeks.


Light is very important in each stage of the life cycle of cannabis plants, but in the flowering stage it is key to maintain a photoperiod of 12 hours of light/12 hours of darkness. When the plant is resting in total darkness, the grow room should not be opened because light pollution can slow the flowering process and even revegetate the plant or produce hermaphrodite flowers.

Temperature, humidity and ventilation

Cannabis plants in the flowering stage thrive in temperatures around 18° to 26°C. Temperatures below 17°C can delay plant growth and very low temperatures can irreversibly damage the plant, even killing it. On the other hand, high temperatures also negatively affect the plant. Temperatures above 28°C can cause a variety of problems such as slow growth, burned leaves, excessive water evaporation, and dehydration, among others.

Humidity should ideally be kept between 40-50% at this stage. Higher humidity levels can cause problems like mold, mildew and other pests that are harmful to the plant.

A good fan that moves air around the indoor room helps a lot, but should not be aimed directly at plants. A extractor fan is ideal for increasing ventilation and air movement, which helps reducing humidity. If the fan is not enough, a dehumidifier is definitely the best solution to keep humidity at a desired percentage.

Nutrients, watering and pH levels

The plant needs nutrients throughout its growth but in the flowering stage it is essential that they have nitrogen, phosphorous and potassium. The secondary nutrients that will also be necessary for the proper development of the plant are magnesium, calcium and sulfur. The micronutrients to consider are zinc, manganese, iron, boron, and chlorine. To correctly apply the nutrients you must read the measurements and guides of each product.

Water your plants regularly with clean, chlorine-free or filtered water. Avoid excessive watering and pay attention to a good drainage. To know if the plant is well hydrated, put a finger one or two centimeters into the soil and if it feels dry it is time to water. The pH levels should remain between 6.5 and 7 when they grow in soil.

Flowering stages

Weeks 1 to 3: During this period, plants stretch and grow in size and height. This phase is also known as the transition phase, as plants will suffer drastic changes. The female cannabis plants begins to flower producing pre-flowers and white hairs appear. Towards the end of the third week, the plant begins to sprout at the nodes where the main stem and branches meet.

Weeks 4 to 5: At this stage, the plants stop growing and begin to gain weight. Buds can be seen and the hairs continue to grow. Humidity levels should be between 40-50%. Temperatures should also drop, as they help the flowering process and when lights temperature should be between 18-26°C. This is when we might need to tie or move the plants, so that all the energy is concentrated in flowers growing.

Week 6 until harvest time: We are going to see big, fat, sticky flowers with trichomes. The aromas in the grow room are going to get deeper and deeper. For this stage it is best to reduce humidity levels to 35-45%.

Last two weeks: It is time to wash our roots! This is very important and easy to do. You only have to water the last two weeks without nutrients. You can let a lot of water run through the growth medium (soil, etc.) to remove excess salt and nutrients. This will improve the taste and aroma of our flowers.

When your buds are already full of trichomes, sticky, crystalline and we can see that the hairs of the flowers are orange and brown, the long-awaited moment has arrived. Time to harvest and enjoy!

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