Do Plants Need Direct Sunlight, or Just Light?

When discussing growing marijuana indoors, one of the things you will hear growers talk about the most is lighting.

Cannabis is a plant that grows naturally outdoors, because it gets full sunlight during the day. Indoor growers need to be able to recreate this sunlight artificially in order to achieve the best results and produce the highest yields.

So, they use indoor grow lights. Is this different from natural sunlight, and how does it affect plant growth? Let’s find out.

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Natural Sunlight vs Grow Lights

As a general rule of thumb, plants that are grown outdoors need about 10 hours of sunlight daily, and this should be direct sunlight without any shadows. Indoor plants need just as much light, so the grower has to use lighting that is specifically designed for growing plants inside. While these lights are not as bright as real sunlight, they will do the job nicely, and they can make up for the lack of brightness in other ways.

When you use artificial lighting, you have total control over how much light your plants receive, which is a good thing. Different lighting systems should be used for different stages of growth. For instance, during the seedling, clone, and young stages, medium intensity, cool-spectrum light (blue light) should be used. During the vegetative stage, it is best to also use the blue light spectrum. When the plants reach flowering stage, switch to warm, red spectrum lighting.

Obviously, the best choice is natural sunlight. Growing plants outdoors ensures that your plants will receive the full amount of sunlight they need for 10 to 12 hours daily, so they soak up plenty of solar energy. But, not everyone has access to an area where there are no trees or other things that can create shade and keep the plants from getting all of that sunlight. When you grow indoors under artificial lighting, you can control the light your plants get for optimal growth and yields.

Grow lights can replicate the UVA rays from the sun, which plants rely on. Plants also need a combination of UVA and UVB rays, which can also be achieved with indoor grow lights. These lights can recreate the full color spectrum of lighting, so your plants get what they need, when they need it, and can grow to be large and healthy, and produce a lot of buds. You can’t completely recreate the effects of Mother Nature, but you can come pretty close.

It just takes a bit of work, and a lot of trial and error until you get just the right setup for your particular needs.

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Using Grow Lights

If you are growing plants indoors, you will need to have full-spectrum lighting for the best results. These days, LED lights are becoming more and more popular with growers, for a variety of reasons. To begin with, there is much less of a financial investment with LED lighting than there is with other types of indoor grow lighting. Also, LED lighting is more energy-efficient, so you won’t see a huge increase in your electricity bills.

One of the biggest advantages of LED lighting is that it doesn’t give off nearly as much heat as other types of bulbs. This means that there is less of a risk of heat damage to your plants. They are also much safer to use, because they stay relatively cool to the touch. These lights are available in a variety of wattages, and different shapes to enhance their effectiveness. Generally, home growers tend to use bulbs with lower wattages, in the 200 to 600 watt range.

Controlling the Growing Environment

One of the best reasons to grow indoors with grow lights is the fact that you get to control the growth environment. You can decide how intense the light needs to be, when to use the various color spectrums, etc. to produce the best plants with the highest yields. You can also control the oxygen and airflow, which is also important for plant growth. There is little risk of pests when you grow indoors, and your plants won’t be affected by bad weather. Light intensity will be constant, with no risk of shadows.

Best Bulbs for Indoor Growing

There are three types of bulbs that are generally used for growing cannabis successfully: fluorescent lighting for seedlings, clones, and immature plants; metal halide light in the vegetative stage; and high pressure sodium light during the flowering stage. Or, you can use full spectrum LED lighting during all of the growth stages. Not only is it a good light for all stages, it is also much more economical than other types of indoor grow lighting.


There will always be arguments for and against indoor growing with artificial lighting. Those who like it, like it a lot. But, there are going to be those who say the best weed is weed that is grown outdoors. If you are unable to grow outdoors, and you have space in your home, using indoor grow lights will help you to produce healthy plants with lots of buds.

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  1. I’ve been exploring for a bit for information on this area for growing plants indoors. I stumbled upon this web site. Reading this information was helpful. I have bookmarked the site and will return. Thanks

    • You made some fine points there. I did a search on the issue and found mainly people will agree with your blog.

    • Thanks, Noriko. I gather you know from the article that the spectrum of light used in the source you give to your plants can improve their health and growth rate. Using an artificial light source that is correctly spectrum balanced for the purpose is important, especially if you want to enhance growth or if you have to use a space devoid of natural light. Make sure you check out the review articles on lights designed for growing plants under the ‘Growl Lights’ sub-tab of ‘GROW’ and you can subscribe for upcoming information articles to be sent straight to your inbox!

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