what is the best light schedule for growing weed

This isn’t to say your plant will stop growing and only produce flower at this point. On average, plants will double in height after the begin the flowering stage both indoors and out. When growing outdoors, however, it’s extremely important plants aren’t exposed to light during the 12 hours they’re supposed to be in darkness. Even streetlights or floodlights can disrupt the flowering period. So, if you’ve got that neighbor who leaves on a floodlight all night that shines on your plants, you might want to see if they’d be willing to put it on a sensor.

Many growers will start their grow indoors under lights before moving their plants outside to grow naturally under the sun. Starting seeds or cutting clones in March or April and keeping them under 18-24 hours of light until they’re moved outside in early May or June is common.

Growing your plants indoors means you get to manipulate your environment as much as you want. When growing indoors, you can essentially keep your plants in the vegetative stage as long as you desire by keeping plants under light 18-24 hours each day.

Typically, the goal of growing weed is to have a large yield when it comes time to harvest. Whether you’re growing indoor or outdoor herb, light is one of the essential aspects of your grow. The light your plants get throughout their entire life cycle will have a tremendous impact on how much they weed they produce.

If you are growing outdoors , it’s vital you keep your plants inside until all danger of freezing temperatures is over. The last thing you want is for a late-spring snowstorm or sudden drop to freezing temperature to kill your plants. Once all danger of a cold snap has passed, plants will remain in veg outdoors from late spring until late summer.

Light Cycle for Indoor Flowering Period.

If you’re growing outdoors, keep them inside on an 18/6 or 24/0 light schedule until all danger of frost and freezing temperatures are over and you can safely take them outside. Once they’re outside all you need to do is let nature do its thing as the sun rises and sets each day on its own.

When growing indoors, growers will typically put plants on a schedule of 12 hours of light and 12 hours of darkness (12/12) once plants have reached the desired size during the vegetative period. On average, growers veg indoor plants for 4-8 weeks under an 18/6 or 24/0 light period.

If you’re growing outdoors, all you need to do is let nature do its thing. When grown outdoors, cannabis will naturally start flowering on their own. This typically happens after June 21 st , when days begin to become shorter.

It’s important to keep in mind however that it’s not just your light schedule during veg that will ensure a bigger yield come harvest. Some strains, such as Jack Herer and Northern Lights , simply produce more weed. And if you’re growing inside and don’t have high ceilings and a well-maintained grow room, your plants aren’t likely to get as big as you’d like them to be. Big plants with big yields need plenty of space to grow.

The key to growing indoor cannabis is mimicking what happens in nature. When grown outdoors, cannabis starts to produce flowers (buds) when the days begin to become shorter and they receive at least 12 hours of total darkness. All that’s needed to do this is to switch your light schedule from 18-24 hours of “sunlight” each day to 12 hours of light and 12 hours of darkness.

Whether you’re planning on growing indoors or outdoors, knowing the best light schedule to follow will help maximize your yield in the end. If you’re growing inside and height and space are not a big issue, letting your plants stay in the vegetative stage on an 18/6 or 24/0 light schedule for at least 60 days (8 weeks) is your best bet to grow the most bud.

Marijuana plants don’t begin to flower until they begin to receive 12 hours of uninterrupted darkness. Until then, they’ll continue to stay in the vegetative stage. You can essentially keep your plants in veg forever as long as they’re receiving 13 hours or more of light each day.

Until plants have 12 hours of complete, uninterrupted darkness they will stay in the vegetative stage. They only begin to flower when they’re exposed to 12 hours or more of darkness each day.

That being said, they also need plenty of light to reach their maximum potential. This is why some growers give their plants 24 hours of light each day. Stick with 18-24 hours of light during the vegetative stage and your plants will reach their maximum potential before it’s time to manipulate the light schedule to make them flower.

There are two major cycles of growing marijuana. These are the vegetative stage (when plants are growing) and the flowering stage (when plants produce flowers or buds).

Outdoor Vegetative Light Period for Maximum Harvest.

Even when growing outdoors, many growers will start their plants inside to ensure they can grow as large as possible. When in veg, plants should be kept under grow lights for a minimum of 18 hours (commonly known as 18/6). Some growers will keep plants under 24 hours of light during this time (known as 24/0) to allow their plants to grow as big as possible.

Being able to manipulate a plant’s light schedule makes it possible to achieve higher yields when it comes time to harvest. When plants are in the vegetative stage, the more light they receive the larger they will grow.

Once the vegetative and flower stages are over (anywhere from 3-6 months), it’s time to reap what you’ve sown and harvest those big, beautiful buds.

Indoor Vegetative Light Period for Maximum Yields.

Our days only have 24hrs, so after 12hrs of darkness , the maximum hours of light we can give them is 12hrs.

When flowering outdoors, you have to be really careful and plan ahead. As you may know, every season has a different cycle and this will determine how long your plant grows before starting to flower.

By crossing with Ruderalis, cannabis strains can have its characteristic of automatic flowering.

Photoperiodic Plants.

When you feel like your plants have grown enough, you can simply change the cycle from 18/6 to 12/12 by adjusting your timer .

Most growers using this schedule leave the light on at night which is usually colder and off during the 6 hotter hours of the day, allowing you to save up to 25% electricity while keeping the growing conditions on point.

Just like in the vegetative stage, when in the flowering stage your plants need the proper amount of light, so if you want your plant to develop to its maximum make sure you buy the best weed light fixture you can. Cannabis flowering stage lighting is very important, i f they don’t get the amount they need while flowering, the buds won’t develop properly and won’t produce the maximum amount of trichomes they can, resulting in lower yields and buds with less quality.

Now, this schedule is a good choice if you’re growing in winter, for example, and want to keep your cannabis plants warm but for some strains, it may be too much so you should be careful.

All of these cycles have their pros and cons, there’s no better cycle in general, each one will work better depending on the growing conditions and specific strain you’re growing so we highly recommend that you experiment with the different schedules mentioned.

As said above, photoperiodics flower in a 12/12 cycle. When growing indoors we keep it the same, although it can be easier to flower indoors because you don’t have to plan ahead .

Autoflowering Plants.

Now, if you’re an autoflower grower and want to experiment with new things, you can also try the different cycles mentioned in the table. To help you understand better, here’s a couple of things you should have in mind when dealing with the different cycles for autoflowering plants.

Growing your autos under 12/12 won’t harm your cannabis plants but it’s most likely that the quality and quantity of your harvest ends up not being what you expect.

Failing to provide them a good amount of light in the flowering stage will result in airy buds, low yields, and your plant can become weak and unhealthy.

Obviously, you’ll be spending a bit more than when growing under 18/6 but the better quality and yields it’s sometimes worth it for some growers.

Light cycle for photoperiodic and autoflowering cannabis plants.

Marijuana flowering stage lighting is super important ; This is because marijuana starts the flowering stage when they receive at least 12hrs of darkness, while still needing the maximum illumination possible to produce buds.

This is used by all farmers, independent of the kind of plant they’re growing, the downside is you will need a greenhouse to be able to do this, as you need to block all lights from coming in and this can be really hard to achieve without a structure to firmly hold the tarp.

This happens because if they get less light, they have a shorter period where they can perform photosynthesis, ending up absorbing less energy which won’t allow them to reach their full potential; As said before, this won’t harm them but will result in a decreased potency and yields.

To give you an example, marijuana outdoors in California only flowers from September to March. So if you were to cultivate a plant starting in April it would grow for 5 months before starting to flower, in September, resulting in a huge plant .

In the flowering stage, the amount of light your cannabis receive will influence the quality, density, and yield of the buds. This means the buds will produce more resin and grow denser the more they receive, resulting in a higher yield.

What keeps cannabis in the vegetative stage?

The vegetative stage is one of the most important parts of the life of your cannabis plant.

Some outdoor growers start their plants indoors to give them a headstart before putting plants outside.

So indoor growers have a choice to flower their plants whenever they want… When is the best t ime to start flowering your cannabis indoors?

Flowering – Flowering (Budding) Stage leads to Harvest – Give 12 hours light & 12 hours dark each day.

The indoor grower will need to artificially induce flowering/budding in plants by changing the light schedule so the plant receives only 12 hours of light a day, and 12 hours of uninterrupted darkness.

Cannabis is a "photoperiod" plant, which means the amount of light received each day decides when the plant starts flowering or making buds. This article explains how much light a day your photoperiod cannabis plants need to grow and start budding, so you get to a happy harvest day. What about auto-flowering strains?

Outdoor growers wait until their cannabis plants start naturally flowering on their own, usually after mid-summer when days start getting shorter than 12 hours.

Don't want to worry about light schedules? For growers that don't want to pay attention to light schedules, there are auto-flowering strains of cannabis, which will automatically go through their whole life in about 3 months no matter what light schedule is provided. For some growers, an auto-flowering strain may be more simple than a traditional (photoperiod) strain.

During the entire vegetative stage the plant does not produce buds at all. It only grows stems and leaves. During the vegetative stage plants tend to grow very fast, especially when conditions are right.

While not technically a "stage," all grows start with cannabis seeds or clones.


The vegetative stage is the growing stage of the plant. When in veg, cannabis plants grow bigger and taller, growing only stems and leaves. As a grower, you are able to control the size and shape of your plants in the vegetative stage using simple training methods.


Whether you're growing indoors or outdoors, you must make sure your cannabis plants get at least 13 hours of light each day to stay in the vegetative stage. If your plant gets a few long nights, it may start budding before you want.

Vegetative – Seedling or clone leads to Vegetative Stage – Give 18-24 hours of light a day.


The plant can receive as much as 24 hours of light a day while in the vegetative stage. Many indoor growers provide 18-24 hours of light a day (known as 18-6 or 24-0 light schedules) during the vegetative stage to encourage faster vegetative growth.

Most indoor growers provide 18-24 hours of light a day (known as 18-6 or 24-0 light schedules). Giving your cannabis plants more hours of light each day in the flowering stage will encourage faster growth.


It's important to make sure plants aren't exposed to light at night during their dark period, even street lights or spotlights, as this can prevent cannabis plants from flowering properly.

What is 12-12 Lighting?