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Cannabis Guide

Vegetative Stage To Flowering Stage

by Neal Brown . Updated: March 31, 2022

Cannabis Guide: Vegetative Stage To Flowering Stage

Transitioning Cannabis From Vegetative To Flowering

In the wild, cannabis plants thrive in hot sunny weather. Most strains are short-day plants, meaning they need to have at least twelve hours of darkness to get the message that it’s time to flower. In nature, this is achieved as the earth slowly tilts away from the sun as high spring becomes summer. The change in daylight hours signals to the plant that winter is coming and it’s time to stop producing leaves and start producing reproductive parts. With our selective breeding of cannabis, this process has intensified, and now it happens artificially over just a few weeks. Growers call this flipping or switching the plant.

The difference between a mediocre yield and a spectacular yield is in how you treat the plants in the transition space between vegetative and flowering phases. Knowing when to flip the switch, especially in the case of indoor growing, is everything. It’s also vital to be giving your plants the right food and environment when they’re being flipped, as both will make a huge impact on their yield. It’s not just about lighting and timing, it’s about whether the conditions of your space are right for supporting the gorgeous buds you’re hoping to get from the plant. It is advised to pick the strains you’ll be growing based on what kind of space you have. A large warehouse with plenty of room for fifteen-foot sativas and an army of gardeners will be flipped differently than a couple of indicas on the back porch.

When Should I Switch My Cannabis Plants From Veg to Flowering?

Common wisdom concludes that you should wait sixty days from germination to make the switch from the vegetative phase to flowering. This gives plants ample time to build strong root systems before starting their flower production. Knowing when to switch your plants is a much more complicated decision that should be based more on the plant’s specific situation rather than just common wisdom. The golden rule is to keep your plants in the vegetative phase for as long as possible to maximize their yields without risking burning your crops. Using LEDs instead of traditional grow lights can help but the genetics and environment you are working with will determine how long your plants stay in the vegging phase. Pure sativas should be flipped when they have filled one-third of the growing space. Indicas and hybrids should be flipped when they have taken up fifty percent of the space. When using a Screen of Green (ScrOG) technique to make a bunch of little plants flower early, flip them once they have all reached a foot in height maximum.

If your plant has recently gone through any kind of stress, it’s best to let it recover first. If your plants have had issues with pests or mold, eradicate these and give them a week or two to recover before flipping. It is much harder to get rid of infections and pests when a plant is flowering. It’s the same if you are using any kind of low or high-stress technique. Let the plants recover before flipping them.

How Do I transition from vegetative to flowering?

When you are sure that it’s time to flip your plants, start by switching their photoperiod. Instead of sixteen hours of daylight to eight hours of darkness, or however, the strain likes it, switch to twelve hours of daylight, and twelve hours of darkness. Indoors, this means switching lighting schedules, and outdoors it’s all about blackout tents. Let the plant adjust to the new schedule for a few days before gradually adjusting the temperature, humidity, nutrients, light intensity, CO2 availability, and airflow.

Cannabis plants are wind pollinated. To trick them into giving you their absolute best and most resinous flowers, it has to feel like the best possible weather for viable pollen to be blowing past. That means reducing the relative humidity in the room by at least ten percent, from a range of fifty to seventy percent down to between forty and sixty. The temperature can be anywhere between eighty and sixty-eight degrees Fahrenheit depending on the strain. Increase the amount of light intensity over the first two weeks of flowering, from roughly five hundred and fifty lumens to eight hundred. As you switch the plant, give it a boost of phosphorus and magnesium while cutting down the amount of nitrogen. CO2 and air circulation can be increased, giving the plants plenty of fresh air to work with. All of these will have to be done gradually, in small increments throughout the first two weeks of flowering. You should start to see changes after the first week.

Vegetative to Flowering Stages

When To Switch Between Growing Stages


Controlling Vegetative Stage to Flower Stage