Best Light Schedule For Cannabis In The Vegetative Stage

by in Cannabis Growth February 27, 2018

The amount of light cannabis receives in this stage will directly impact its health and ability to support the buds.

The vegetative stage has the ability to prepare the plant to support the bud, while also making it grow more and more healthy. Failing to provide a good amount of light will result in an unhappy plant that will be more prone to diseases and bugs.

The proper amount of light in the vegetative stage has the ability to prepare the plant to support the bud, while also making it grow more and healthier.

1. What Is The Light Cycle In Vegetative Cannabis?

Light is extremely important for plants in the vegetative phase because its what they use to photosynthesize and grow sturdy and healthy, so if they get more light, the more and better they grow.

Generally, the most common light cycle for the vegetative stage is 18/6 (light/darkness) but it can be any combination of light and darkness (like 20/4, 19/5, 17/7) as long as they dont get more than 12 hours of darkness per day as this will trigger flowering.

light schedule for cannabis

Light cycles for cannabis vegetative stage.

Have in mind that giving your plants less light will cause them to develop slower and if youre not that experienced, you should follow the 18/6 light cycle and only give them more light (like 20/4) if you know your plant can take it.

Not always giving them more light is going to result in faster or more development and you can harm or really stress your plant by doing this, making them turn into hermaphrodites or showing other heat stress symptoms.

2. Light Cycle For Vegetative Cannabis Outdoors

Photoperiodic Plants

When growing outdoors, the light cycle will solely depend on the season youre in. Each season has a different amount of light and darkness hours, and this will hugely influence when you can start growing your photoperiodic cannabis plants.

For example, in California, we have the following light cycles throughout the year:


December (9/15)

January (10/14)

February (11/13)


March (12/12 of light)

April (13/11 of light)

May (14/10)


June (14:30/9:30)

July (14/10)

August (13/11)


September (12/12)

October (11/13)

November (10/14)

This means that when growing outdoor you have to know the amount of light and darkness you will receive in the next couple of months so your plant develops the way you want to.

Note: Have in mind the information above is exclusive to California, you should get information about how is it in your area. That information can easily be found on the internet.

lightcycle cannabis

When growing outdoors, the light cycle will solely depend on the season youre in.

Autoflowering Plants

On the other side, autoflowering plants do not have a vegetative stage and start flowering directly from seed, not depending on a light cycle to do so.

This means you can grow autoflowering strains outdoors all year long. Although the amount of light and other factors like humidity and temperature may have an influence on the development of your plant, they will definitely vegetate and develop properly outdoors at any given time, before flowering.

3. Light Cycle For Vegetative Cannabis Indoors

Photoperiodic Plants

As you may know, when growing indoors we are responsible for maintaining all the elements of the environment, in the beginning, it can be a little bit hard but when we get more experienced it can have various advantages.

Like we said above, photoperiodic cannabis depends solely on the amount of light and darkness to start flowering, which can be tricky for new growers outdoors but when growing indoors, we are in full control of everything, including the light cycle.

Unlike autoflowering cannabis, photoperiodic plants indoor can vegetate for a long time and will only flower when we change the light cycle.

This allows us to vegetate our plants as long as we want and then flip them to the flowering stage when we have met our goals in the vegetative phase.

100watt cannabis grow light

As long as you keep your plants in an 18/6 (or other combinations with no more than 12hs of darkness) they will continue to grow.

Autoflowering Plants

Autoflowering cannabis will flower independently of the amount of darkness they get. Obviously, giving them too little light like a 5/19 light cycle will make them seriously underdevelop but they will flower either less.

More experienced growers can experiment with different light cycles, some growers even saying they got the best results by giving their autoflowers 24hs of uninterrupted light. We encourage you to experiment also, but be aware that too much or too little light may stress your plants.

Different light cycles with autoflowering cannabis are also used to save electricity, by giving your plant a little bit less of light (like a 16/8) it will sum up to an important amount at the end of each cycle.

Even though it can affect the yield, removing only 2hs of light per day shouldnt make a big difference on the plant and can save you a couple of bucks.

If you are still new to growing cannabis and want to guarantee your harvest, start with an 18/6 light cycle, and after you get a little bit of experience, it will be easier to read your plants signs and you can start experimenting with other light cycles.

4. In Conclusion

The vegetative stage of cannabis is super important. In this stage cannabis is building up strength to be able to support all the buds in the flowering stage. There’s nothing as the best light cycle for the vegetative stage, the light cycle will depend on a lot of factors that are individual to each grow room.

It is crucial that you give the amount of light and nutrients it needs so she can develop properly and be ready for the next stage.

Even though it mostly depends on genetics, the amount of light your plant will be able to receive is a decisive factor in the amount and quality of flowers it will produce.

If you don’t know which one to follow, we recommend providing a 18/6 light cycle for your cannabis plants in the vegetative stage as this cycle has been proved by a lot of growers to work really well, allowing the plant to develop properly.


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