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Cannabis Light Schedule: All You Need to Know

cannabis grow room with LED lights

Whether you’re planning to grow cannabis for recreational or medicinal reasons, the end goal is always the same, getting as much bud from your plants as possible.

One of the best ways to maximize your yields is by paying close attention to Cannabis light schedules, as it’s one of the most important aspects of weed growing, next to quality of soil, nutrients and topping.

cannabis grow room with grow lights
cannabis grow room with grow lights

Exposure to the correct amounts of light has a quintessential effect on how big your cannabis will grow, which in turn will directly increase the amount of buds your plants will produce.

Cannabis plants have two important stages in their development. The vegetative stage is where plants gradually grow and develop, and the flowering stage is when female plants reach maturity and begin to produce flowers.

These crucial developmental stages require their own specific Cannabis light schedules, and in this article we will be discussing the lighting requirement for both the vegetative and the flowering stage, for both indoor and outdoor growing.

We will first talk about the light schedule for the vegatative stage, for indoor and outdoor conditions.

Cannabis Light Schedule for the Vegatative Stage

As we already mentioned, adequate light is essential for maximizing yield, and since cannabis plants do most of their growing in the vegetative stage, it’s absolutely crucial to have proper lighting conditions during this time.

The majority of cannabis growers like to start the growing in indoor conditions, as this allows them to carefully nurture their plants, so the plants are able to thrive when they are placed outdoors.

There are two main methods for light schedule during the vegatative stage, commonly known as 18/6, and 24/0.

The 18/6 method implies that the plants are going to be exposed to grow lights for 18 hours during the day, and receive a total of 6 hours of darkness each day.

While the 18/6 method is definitely the most popular option, some growers like to kick it up a notch and expose their plants to light 24 hours a day during the vegatative stage.

Since the plants are receiving light during the entire day, this method is known as 24/0.

It’s important to mention that cannabis plants grown in indoor conditions can be kept in the vegatative stage indefinitely, as they require 12 hours of continual darkness to enter the flowering stage.

This natural mechanism of cannabis plants allows the growers to precisely determine when they want their plants to start flowering, and can keep them in the vegatative stage until they are sufficiently developed.

Vegetative Stage Indoors

Since we already stated that weed plants grown indoors typically need to be exposed to grow light between 18~24 hours per day, we are also going to cover some other important aspects for the vegetative stage in indoor conditions.

Even though indoor growing allows cultivators to extend the vegetative phase for as long as they want, other factors also come in play that ensure the quality of the yield.

For instance, adequate room is essential when growing cannabis indoors. If your grow room doesn’t offer sufficient space, the plants cannot reach their full potential.

Topping your plants is also essential, as it makes them wider and busher. A topped plant allows the light to reach more surface area, and this in turn increases the overall size of the buds.

Finally, if you’re looking for massive yields at the end of your growing, it’s important to pick a strain that is able to produce a massive amount of buds.

Vegetative Stage Outdoors

Cannabis plants intended for outdoor cultivation typically start their journey with high quality cannabis seeds grown in a controlled room. They stay in the closed environment till they begin to develop and mature. Then they are replanted outdoors.

Such plants usually enjoy the 18/4 or 24/0 light conditions for a few months. Most cannabis growers move them outdoors in May or June.

cannabis in vegetative stage outdoors
cannabis in vegetative stage outdoors

The greatest threat in outdoor cannabis growing are freezing temperatures, so it’s essential to avoid sudden drops in temperature as they can greatly damage or even destroy your plants.

Cannabis plants grown outdoors generally remain in the vegetative stage until late summer, when light conditions start changing, which kickstarts the flowering stage.

Cannabis Light Schedule for the Flowering Stage

As we already mentioned, cannabis plants require at least 12 hours of darkness in order to start with the flowering stage. If these conditions aren’t met, the plants will remain in the vegetative stage.

We are now going to cover how to set up the ideal light conditions for the flowering stage for both indoor and outdoor growing.

Flowering Stage Indoors

After keeping the cannabis plants in the vegetative stage (usually for 4 to 8 weeks), cultivators change the light conditions to start the flowering stage and plants begin to produce buds.

This is generally achieved by setting the grow light to 12 continuous hours of light, and 12 hours of complete darkness. This light setting is usually abbreviated as 12/12.

Flowering Stage Outdoors

Since plants rely on the sunlight to grow and develop when they’re grown outdoors, there isn’t really much to do regarding artificial Cannabis light.

Cannabis plants typically enter the flowering stage on their own at the end of summer when days get shorter, which usually happens during late June.

But, what you can do is to make sure that your plants aren’t exposed to any light sources during the night.

Even weak light sources like flood lights or street lights can interfere with the natural mechanism of your plants and interrupt the flowering process.

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