LEDGrowlights101 is reader-supported. If you buy via links on our site, we may earn an affiliate commission at no extra cost to you.

The Significant Role of Light When Growing Cannabis

Last Updated on

It doesn’t matter if you grow your cannabis plants outdoors or indoors, they’ll need light, either way, to grow and mature. Your plants can’t keep living and growing if they don’t receive enough light from the right type of lighting. Except during the germination of seeds, you’ll be needing light for all stages of your plant’s life.

Today, let’s learn about the lighting systems, various temperatures, and colors, the different sources of light, the positioning of lights, as well as the right amount of light for each growth stage.

Lighting Systems

If you’re going to plant your marijuana outdoors, you don’t need lighting systems because the sun’s light is already present and is for free! However, if you’re going to plant marijuana indoors, you’ll come across various lighting systems. These lights might include bulbs, reflectors, ballast, timers, and more. Each type has its advantages and disadvantages. What you need to consider is if it can provide the sufficient amount of light for your plants. In case you didn’t know, lighting systems activate the hormones found in your plants to help them grow faster. This makes them similar to sunlight.

Different Sources of Light

Aside from our glorious sun, there are other sources of light you can rely on when cultivating your marijuana plants indoors. Don’t worry; though artificial, they’re made to replicate natural sunlight.

Here are the three common sources of light you’ll encounter when you search for the perfect light for your plants:


  • High-Intensity Discharge or HID lamps aren’t as widely distributed around the planet, but they are believed to be effective artificial sources of lights for any indoor plant. The most common are the metal-halide and High-Pressure Sodium (HPS).

metal halide lamp

  • Light-Emitting Diode or LED lights are now considered the most efficient artificial light for indoor gardens. Although they are priced higher than the previous two, they have lower total operating costs which make them beneficial in the long run. Get to know the other benefits of LED lights now!

King Plus 1000w

Here’s an informative YouTube video comparing HID lights and LED lamps to each other:

Temperatures and Colors

Don’t choose a lighting system just yet! You still have to do your homework; that is to study the light’s temperature and color. Temperatures that are extremely high can harm and burn your plants, and each color offers a different influence on them as well.

If you’ve read a few articles about lights, then you know that growers usually use lights with a maximum wattage of 1,000 to grow cannabis sativa. That’s because if you go further than 1,000, your plants will be damaged. It’s then safe to use less than 1,000 only.

For your information, one cannabis plant requires at least 3,000 lumens of light for every square foot. So if you want to achieve the greatest productivity, you should provide 7,000-10,000 lumens of light for each square foot.

Positioning of Lights

After considering which type of lighting system you should get, you should install it correctly. If your lighting system releases too much heat like CFL and HID lamps, you should hang them more than 14 inches away from your marijuana plants. Placing them too near can damage your crops. But for LED lights, place them 10-14 inches above your plants. You don’t have to worry about them damaging your plants because LED grow lights release less heat but more light compared to the two.

Sufficient Light

grow tent with cannabisEach stage requires a different amount of light. Make sure to follow the guideline below:

  1. Seedling phase – Requires 16-18 hours every day
  2. Vegetative stage – Needs 18-24 hours of light daily
  3. Flowering stage – Requires 12 hours of light each day

Don’t supply less light; that’ll slow down the plants’ growth. Likewise, don’t give them more than they need for the day; doing so might damage and burn the plants.


I know I probably don’t have to mention it again, but light has a significant role in the growth of your cannabis crops. Because that’s the case, you have to consider the quality of lighting system you have in mind as well. You should also examine the size of your indoor garden. CFL and HID lights need extra fans because they build up heat, and they also need a larger room because they can’t be placed side by side with little space. On the other hand, LED lights can be used even if your growing area is small because they don’t build up heat and don’t require additional fans.