how much sun does marijuana need

Growing Cannabis Outdoors: How Much Sunlight Do Plants Need?

Published : Jun 28, 2018
Categories : Other subjects

Growing cannabis outdoors encourages fantastic natural growth, allowing plants to grow much bigger than they would indoors. But there is a big difference between growing photoperiod and autoflowering seeds outdoors. Depending on your location, you may want to choose one type of seed over the other.

Sunlight is what encourages natural leaf and stem production in cannabis, allowing it to flourish and reach heights that can far exceed indoor grows. With an outdoor grow, the best yield will come from plants that have the most access to sunlight (in favourable conditions), so this will always be key to take into consideration when moving your cannabis growing skills outside.


Cannabis is a hardy plant—but before you start growing, it is best to find a spot with a lot of sun exposure. This could be a clearing or a particularly open part of your yard, away from trees and other obstacles that might prevent your plant’s leaves from utilising as much solar power as possible. It’s always a good idea to start growing your photoperiod cannabis in early spring to take advantage of the valuable solar energy early in the growing season. Darkness is what triggers flowering in cannabis, so starting your grow in the springtime will ensure your plant receives as much sunlight as possible by the end of the summer.

Ultimately, the objective for the outdoor grower is to make sure your plant is getting at least five hours of direct sunlight and five hours of indirect sunlight each day; however, days tend to be longer during the middle of the growing season, where the sun can be out for much longer. As a short-day plant, a 12-12 hour photoperiod is the easiest to work with when planting cannabis, and with most strains, it bears excellent results. Growing cannabis is not an exact science, and it takes time to build the skills necessary to support a flourishing grow—but if you are dedicated to the task, you may be able to achieve great results.

Now, you might have to make some compromise for your ideal spot after you have taken issues like water access and security into consideration. If you choose to grow photoperiod seeds, your plants will require more attention. Don’t forget to be patient and use as many resources as you can to acquire the best data on your plant’s climate, such as a sun calculator.


Photoperiod cannabis plants use photoreceptors to sense forms of phytochromes or cytochromes created by light. Therefore, the photoperiod of cannabis can be considered in terms of the hours of light a plant receives over a 24-hour time period.

One benefit of selecting photoperiod strains is that you are able to take cuttings of your best plants and use them to breed new plants. However, you will always have to pay close attention to the amount of sunlight your plants are getting, and spend a lot more time getting rid of males that could pollinate your crop.

A problem that may occur when growing photoperiod is late blooming. Greenhouse growers can make use of tarps and plastic sheeting to reduce the hours of sunlight and trigger the flowering stage, which will be especially important in the Northern Hemisphere, where the nights become shorter. Using this method requires you to always remove the shade material before sunrise.


Most photoperiod strains tend to begin flowering when the hours of daylight the plant receives drops below 15. Yet, this type of seed is able to stay in its vegetative stage indefinitely as long as it receives at least 15 hours of sunlight each day.

By finding the point at which your plant will be receiving 18+ hours of sunlight each day, you will be able to determine the best period for vegetative growth. The next important factor is finding when sunlight drops below 12 hours in order to trigger flowering and eventually harvest.

When seeds are planted in the spring, plants should shift steadily from their vegetative stage to the flowering stage after the solstice. As the nights get longer, outdoor photoperiod strains begin to bloom more steadily; some late-blooming sativas can continue to grow until late-autumn. The kind of sunlight the plant receives will directly affect the way in which it develops.

It is important to take extra care when growing this type of seed. You must always ensure that your plant receives 5 hours with and 5 hours without continuous sunlight. Try not to rush over this crucial detail. It is a steep learning curve, but light levels will determine the rate at which your crop grows.


The fastest-growing and smallest plants are typically autoflowering seeds, making them perfect for a stealthy operation. This allows for a low-maintenance and cost-effective grow with fast results. Don’t forget to learn the approximate growth and flower time of the strain you are using, so that you can start growing your next seeds before harvest.

For guerrilla growers, it might be a great idea to pick several locations to plant your autoflowering seeds. Known as the “plant and forget” method, this technique allows you to simply put a seed in the ground and forget about it (for a few months). When you come back to your locations, you will have already increased your chances of getting a crop. You might not get the biggest yields, but if you have concerns about getting caught, this is a simple sidestep.


Autoflowering strains are developed so that they are able to flower under nearly any light conditions. This makes them great for beginners, and keeps things simple for all growers. But it is still important to get as much sunlight as possible when growing autoflowering seeds outdoors. Your final yield is a direct reflection of this.

Picking the right time to grow autoflowering seeds is crucial. You may find that if you start at the beginning of summer, you can harvest multiple crops by the end. Try to pick a strain that will get the most out of your specific growing conditions. There will always be more for you to consider when growing in northerly regions. You can use the preset life cycle of your seeds (usually printed on packaging or available on seedbank websites) in order to build a grow plan and pick a strain that will work best with your climate.

A Guide On Mixing Different Cannabis Strains Together

Take a look at our tips for growing photoperiod and autoflowering cannabis strains under the sun. There are multiple aspects to consider.

Cannabis Light Periods – What do I need to know about marijuana light cycles? (length of sunlight hours each day)

If you’re growing a cannabis plant grown from a random seed (“bagseed”), unless you somehow have an auto-flowering seed, you will need to understand about cannabis life stages and how they are affected by light periods.

If you don’t understand light periods, your plant may never start making buds! The light schedule experienced by your plant will actually change its life stage. Learn more…

Cannbis plants have two life stages:

1.) Vegetative – Seedling or clone leads to Vegetative Stage

  • Give 18-24 hours of light a day (indoors)
  • Cannabis grows only stems and leaves

2.) Flowering – Flowering (Budding) Stage leads to Harvest

  • Give at least 12 hours of uninterrupted dark each day (short days)
  • Cannabis starts growing flowers/buds

The first stage, “Vegetative” begins when marijuana plants first sprout, at the beginning of their life.

Most indoor growers give their cannabis plants 18-24 hours of light a day during the vegetative stage. The exact number of hours needed to keep a plant in the vegetative stage is dependent on the strain, but 18+ hours/day will keep basically all cannabis plants in the vegetative stage.

Outdoor growers plant their seeds in Spring when the days are naturally longer. In the wild, cannabis seeds naturally germinate in the Spring.

For an indoor grower, when a plant is about half the final size you want it to be, you should change it over to the “Flowering” stage. This is the stage when your plant starts growing buds.

You do this by changing your light so that it only shines for 12 hours a day, and the other 12 hours a day your marijuana plants are kept in TOTAL darkness.

After 2-3 weeks of the 12-12 light schedule, most cannabis plants will show the first signs of their gender (they either are a female plant which starts growing buds, YAY! or they are a male plant which start growing balls/pollen sacs, NO!).

Boy cannabis plants don’t give you any usable amounts of THC, so most growers toss them on sight. These male plants can also impregnate (pollinate) your female plants, which causes your female plants to produce seeds and less buds.

So unless you’re planning on breeding, it’s important that most growers destroy male plants as soon as you notice them growing grape-like balls where their buds would normally be.

Unfortunately, about 50% of all regular (unfeminized) cannabis seeds are male (though this varies from strain to strain, and from environment to environment). Fortunately for small growers, you can purchase feminized (all-female) seeds so you don’t have to worry about male plants if you don’t want to. Learn more about buying seeds.

When does a cannabis plant start budding?

Marijuana plants have an internal process that allows them to detect how long they receive darkness each night. This is because they are a “photo-period” plant, specifically a “short-day” plant which means these plants start making flowers/buds when days start getting short.

In the wild, as the days get shorter and nights grow longer, a marijuana plant “realizes” that winter is coming and will start budding/flowering. It “knows” it’s approaching the end of its life cycle so it frantically starts making buds in time before winter.

When growing marijuana outdoors, a grower doesn’t need to do anything to induce flowering because the sun will take care of things on its own. It’s just important to make sure that there are no lights shining on your plants during their night period (which will disrupt their dark cyle).

However, when growing weed indoors, a marijuana gardener will have to fool their plants into “thinking” winter is coming to induce flowering and kickstart the creation of buds.

This is done by changing the plant’s light schedule to 12-12, where the weed plants gets 12 hours of light a day and 12 hours of total darkness.

You’ll get the best results if the start and end time for the light is exactly the same each day, which is why most growers end up getting a timer to flip their lights on and off, like an automatice light switch.

I tend to set my timer to shine line from 8pm-8am. This gives me time to check on my plants at night when the lights first come on, and I can also check them quickly in the morning before I go to work. It also keeps things cooler since the lights go on at night.

But ANY 12 hour period will work, as long as you remain consistent.

Check out my cannabis grow light guide for more info about picking out suitable lights!

Photoperiod dependent strains vs. auto-flowering strains

So all strains of cannabis that respond to light in this way (where the light period effects what stage they’re in) are called “Photoperiod dependent” strains.

Auto-flowering” marijuana strains pretty much ignore how much light they get each day. Generally you don’t run into these unless you buy them particularly from a cannabis seed bank.

Cannabis Light Periods – What do I need to know about marijuana light cycles? (length of sunlight hours each day) If you’re growing a cannabis plant grown from a random seed (“bagseed”), unless