What’s the Ideal LED Grow Light Distance From Plants?

What's the Ideal LED Grow Light Distance From Plants

Many people often debate about whether growing marijuana is an art or a science! We say it is both of them. Just look at the simple case of grow lights – it is a scientific process to choose the grow lights but it is quite an art to hang it in just the right place so that your plant gets enough heat and light! In this article, we take a closer look at what is the ideal LED grow light distance from the plants – how to grow your weed in the best possible manner!

However, before we head into that, let us talk a little bit about how to grow weed indoors and the role that LED lights play in it – when it comes to growing weed, there are two ways to do it. You can either choose to grow it outdoors by burying your marijuana seeds in the mud and then waiting for them to grow naturally, or you can choose to grow the seeds indoors by creating an indoors-setup which emulates the natural environment – this includes setting up grow lights (which emulate the warmth and light of the sun) and providing water and ventilation which support growth. 

Growing weed indoors has a number of benefits as compared to growing weed outdoors, because when it comes to indoors growth, you have a much greater degree of control over the factors that affect the growth. For instance, outdoor growth may get hampered  due to bad weather, the prolonged absence of sun, excess of rain, too much heat, etc. However, when it comes to growing marijuana indoors, you can actually customize your setup exactly the way you want it to be.

The Need and Benefits of Grow Lights

Now before we talk about the ideal distance that your grow lights must hang at over the plants, let us first take a moment to appreciate grow lights and understand why LED grow lights are the best for your plants.

You need a grow light for your plants because when you grow your cannabis plants indoors, you do not have access to sunlight, which is the most important factor for any plant’s growth. Sunlight acts as the primary source of energy and it is also important because that is the direction most plants grow towards. Sunlight helps promote photosynthesis which is the process where plants convert light into energy. Light is also needed by plants to create various pigments (particularly important in case of marijuana plant as this decides the flavour).

Hence, you need grow lights to replace sunlight. The best part here is that unlike sunlight, which you cannot actually control, you can control grow lights. For instance, a plant like marijuana needs about 18 hours of light during its early-growth phases, but it is not possible in most places under the natural sun. However, you can emulate such a situation in a controlled environment to ensure that your plant gets the best possible care. 

  • Why Are LED Grow Lights the Best Option for Your Marijuana Plant?

LED grow lights are the best when it comes to an indoor growing setup! This is because they provide a much better wattage of light compared to some of the older/traditional lighting systems (fluorescent lights/high pressure sodium lamps/metal halides) while also not carrying any harmful chemicals inside them. Moreover, they are much more energy efficient and help save electricity costs. Furthermore, LED grow lights tend to last for much longer (about 50,000 hours on an average) compared to older forms of lighting. The best option for most modern-day growers is to get panels of full-spectrum LED grow lights which allow them to easily provide light to different kinds of plants through different kinds of phases of their growth.

Let us now head into the ideal distance between LED grow lights and plants.

What’s the Ideal LED Grow Light Distance From Plants?

It is important to understand that LED grow lights need to be hung at an appropriate distance from plants! Keep it too far and it might not provide the needed amount of light and heat and keep it too close and you risk burning the plants as well as reducing the coverage area. Growers need to consider two factors in mind before they start growing weed indoors – the time that you are providing the light to the plants and the amount of light that you are providing the plants with!

The amount of light you provide is also directly proportional to the amount of heat your provide. The more intensely focused the light is, the higher the levels of heat are! You need to keep a number of things in mind, but the most important of these things is the growth cycle of the marijuana plant. You need to know that in its early stages, when it is still a seedling, the plant requires the most heat and the most light – however, as it grows bigger, the requirement too, reduces. 

During the vegetative phase of the cannabis plant’s growth cycle, it requires between 16 to 18 hours of light. The basic idea here is that summertime is conducive for the growth of these plants and doing this mimics the summertime photoperiod, helping the plants grow in an ideal way. After four to eight weeks of this, most marijuana plants would enter the pre-flowering or early-flowering stage, which is when you need to increase the height and reduce the light-time to about 10 to 12 hours a day. 

Another thing that you should know is that there is a direct corelation between the wattage of the LED light and the distance that you need to maintain from the plant.

Wattage and Distance: How Far Should Your LED Grow Lights Be From Your Plants?

  • 200 Watts – 12-20 inches during the vegetative phase, 8-16 inches during bloom phase
  • 400 Watts – 20-27 inches during the vegetative phase, 13-21 inches during bloom phase
  • 600 Watts – 30-38 inches during the vegetative phase, 18-30 inches during bloom phase
  • 800 Watts – 32-42 inches during the vegetative phase, 19-34 inches during bloom phase
  • 1000 Watts – 36-46 inches during the vegetative phase, 21-36 inches during bloom phase

Ideal Distance For Other Types (non-LED) of Grow Lights from Plants:

Now that you know what the ideal distance of the LED grow lights from the marijuana plants is, you also need to know the distance between non-LED grow lights and your cannabis plants.

  • Metal Halides/HPS Lights

Metal halides and High Pressure Sodium lights are important because the former provides a ‘cool spectrum’ of lights and the latter provides the ‘hotter spectrum’. Halides are great for the vegetative stages and HPS lights are great when it comes to the flowering stages. At about 400 Watts, they should be kept between 7 to 21 inches away from the plants and you can adjust accordingly.

  • Fluorescent Grow Lights

T5s, CFLs, and T12 are Fluorescent grow lights which are also pretty popular with the growers. While you can place the T12 and T5 lights closer to the plants, CFLs should not be kept near to the plants because they allow a lot of heat to be built up which can actually damage the plants. T5s and T12s should be 12 inches away and CFLs should be a little higher but that varies from growth stage to growth stage. 

One of the best ways to determine how far you should keep the light from the plant is by using the ‘hand test’. Keep reading to find out what that is. 


  • What is the hand test?

The hand test, also known as ‘Back of the Hand Test’ is a very basic thing which needs to be done if you don’t really have your measurements right. Place your hand just above the highest leaf and adjust the grow light about a foot and a half away. Keep your hand there for 30 seconds. If it begins to burn in under 30 seconds, it means your lights are too close and they need to be moved up. Move the light a little closer and wait another 30 seconds. This is a rough approximation and should be done only to get an estimate. 

  • Can LED grow lights hurt your eyes?

Looking into any source of light for prolonged period can hurt your eyes. LED grow lights are much better compared to most other forms of grow lights and using them, even for extended hours will not hurt your eyes as long as you use them in the intended way. There’s no need to stare directly into the lights and for a long time – doing which will definitely hurt your eyes. However, under normal circumstances you do not need to fear while using these grow lights.

  • Can grow lights have a negative effect on your plants?

An excess of everything can be dangerous. If you use grow lights on your plants, under the best circumstances, you can get the ‘ideal growth’. However, if you use them a little too much or put them a little too close to your plant, you might end up harming the plant by burning the edges and the tips of the leaves. Too much warmth also leads to excess humidity which is bad for the plants. Hence, it is essential to use grow lights only for the required amount of time and at an appropriate distance. 

  • How long do you need to keep the lights on?

How long you need to keep the grow lights on depends on what stage of growth your plant is in. Especially in the case of marijuana/cannabis plant, you need to keep the lights on for a really long time (about 18 hours) in the early growth phase/vegetative phase. However, in the flowering stage you can reduce this (about 12 hours). However different plants have different light requirements – plants such as cactus can grow with ease even with up to 24 hours of light while others don’t have the same capacity.

  • Does more light mean more growth?

No, more light does not mean more growth, especially when it comes to growing weed indoors. Marijuana plants require a cooldown period as well, so that they can ‘rest’ after producing energy for 18 hours a day. Darkness is as important to the growth of most plants as light is! Your plant would get exhausted and burn out if you keep it under light all the time!


In conclusion, we hope that this article helped you understand what the ideal distance between your plants and your grow lights need to be. We hope it helps you grow just the perfect type of weed which you would enjoy smoking up!

Happy Smoking!


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