Ever wondered How far away should LED lights be from plants? We show you how to evaluate proper grow light distance for yourself, for each of the growth stages for your indoor plants or type of grow light you are using.
As an indoor grower, one of the things that could be troubling is figuring out how far your grow lights should be from your plants.
The truth is, there could be multiple answers to this question, but there is a general rule you can follow, and that is called the hand test.
The hand test is when you leave your hand under your grow lights for 30 seconds and when you find the heat too much to bear, then your lights are too close to your plants.
That’s something you don’t want as too much light, or strong intensity of lights could damage your crops, or worse, it could even kill your plants.
While the hand test could work, there are still different types of grow lights you may use when setting up an indoor garden. This determines the specific distance you should consider when it comes to your grow lights.
Here we will discuss optimal distance between your grow lights and your plants to get enough light coverage for robust photosynthesis and maximum yield in all stages of plant growth, seedling, vegetative and flowering. You can apply this information to HPS, LED T5, or CFL technology.
Importance of Grow Lights When Growing Crops Indoors
Plants require light in order to thrive and when indoors, this is one of the important factors to consider. We need to mimic how healthy plants grow outside and because of that, we need something that will substitute the sun when it comes to giving the plants what they need.
Light, whether natural or artificial, helps plants go through the process of photosynthesis. This is when plants produce glucose through the carbon dioxide, water, and light that they get. They store the glucose in their system so that they can consume it as their food and energy.
Like a lot of things, too much is just too much. Same thing with getting not enough. It just won’t work, so we have to make sure that our plants are getting just the right amount of light they need.
You need to know how long you should be exposing your plants under the light to make sure that you’re doing things correctly, but aside from that, the heat your grow lights produce also has to be considered.
There are different grow lights that you can use for indoor gardening. Some growers use fluorescent bulbs, HPS lights, and LED grow lights. What’s nice about getting LED grow lights is that these have the shades that plants need to thrive. These are the colors red and blue.
Why do Different Grow Lights Need to be Hung at Different Heights?
As you already know, there are different grow lights that you can choose from when it comes to delivering to the light needs of your plants.
However, you need to take note that not all grow lights are entirely alike. Each grow lights need to be hung differently to avoid over and underexposure of your plants to the light.
Even if all of them give the light your plants need, their intensity and spectrum are all different, and it doesn’t mean that you can have them placed above your crops in the same manner.
Here we will tell you what those are and how far you should be placing them from your crops.
HID Light Spacing: How close is too close?
HID or High-Intensity Discharge grow lights can produce a strong amount of heat while it’s turned on. With that said, if you’ll be using these as your light source, this should not be placed too close to your plants as it will quickly dry them up.
Here’s a suggested guide on how far you should be placing the HID grow lights away from your plants based on the wattage:
400W – 600W
12 to 19 inches away from your plants
600W – 1000W
14 to 26 inches away from your plants
More than 1000W
16 to 31 inches away from your plants
Now, even if HID grow lights produce can produce intense heat, it doesn’t mean that it should be placed way too far from your plants.
Underexposure to lights will also cause you a problem. You should really take note of the maximum distance for each wattage to be sure all your plants will get enough light.
fluorescent grow light distance
There are different types of fluorescent grow lights like T5s, CFLs, and T12 so there will be differences when it comes on distancing them from your plants.
T5s and T12s do not really produce enough light to cause light stress or burn on plants but do take note that T5s has higher light output. That said, T5 is still more intense than T12s.
CFLs, on the other hand, can produce heat that can build up, especially if you’ll get the compact ones. However, this is generally not too intense that it produces heat that could kill your crops.
The general rule you can follow when it comes to using fluorescent T5 grow lights is to keep them at least 12 inches away from your plants. When your plant grows, that’s when you can just readjust the distance.
Metal Halides and HPS Grow Lights
These two usually both comes together in kits as they both help in giving the right spectrum to your plants. Metal Halides provide the cool spectrum which is good for the vegetative stages, while the HPS (High-Pressure Sodium) lights are ideal for the flowering stage.
We’ve come up with a guide you may use when it comes to distancing them to your plants based on their wattages.
8 to 12 inches
10 to 14 inches
12 to 19 inches
14 to 25 inches
16 to 31 inches
Remember to keep an eye on your plant’s growth as you need to adjust the distance of your grow lights once the plants grow taller. If you don’t do this, it will hurt the tip of your plants.
How Far Should Led Grow Lights Be From Plants
With right distance, you’ll be able to grow strong and healthier plants or crops as this won’t burn them out. Keep in mind that grow lights as LEDs can easily burn your plant out if it’s placed way too close to your crops.
When plants are overexposed and are grown too close to their light source, you’ll see that they’ll acquire bleaching and have yellow spots all over their leaves.
This could also cause them to have nutrient deficiencies that we’d really need to avoid.
The distance really varies and so there’s nothing specific when it comes to the distance of your LED grow lights form your plants.
When we say it varies, what we consider is the shape, size, and wattage of the LED grow lights that you have.
You need to check the specifications of the LED grow lights you purchased. If it doesn’t have any recommendations when it comes to how you should be placing it in your grow room, tent, or space, it’s always best to contact the manufacturer.
This is why it’s advisable to get an LED grow light from trusted manufacturers or brands.
Unlike other types of grow lights, it could be a bit complicated to know how exactly far your LED grow lights should be from your plants.
Led Grow Light Distance Chart
There’s no exact computation to help you determine how far your grow lights should be from your plants, but here is a guide that we can share with you:
LED grow lights Wattage
Distance from Plants
16 inches or 30 cm from your plan
20 inches or 30 cm from your plants
21 inches or 53 cm away from your plants
12 to 20 inches away from your plants
16 to 30 inches away from your plants
450- 550 watts
20 to 30 inches away from your plants
600- 800 watts
28 to 42 inches away from your plants
900- 100 watts
36 to 46 inches away from your plants
MEASURE HOW MUCH LIGHT YOUR PLANTS ARE GETTING
Keep in mind that LED grow lights can wilt and burn your plants even if they don’t really produce much heat.
If you want to be sure you’re not going to overexpose your plants, you can always have it placed as far as you prefer. What’s important is that all your crops are lighted evenly.
This could be a trial and error process when it comes to perfecting the distance of your LED grow lights from your plants, so be patient and alert to see how your plants are doing with the distance you’ve set.
Generally, it’s safe to say that you should keep the grow lights at least inches away from your plants.
There are flowering plants, like orchids and citrus that require a high light intensity to flower and produce fruit.
This means that the grow lights should be placed closer to these plants. ZZ and Snake plants only need low light intensity, and so your grow lights should be placed farther.
Lux Meter to measure light levels in your grow room
A lux meter is used to measure brightness levels. This could help you have a better grasp of the distance that you should be giving between your plants and grow lights.
Remember that this doesn’t measure the heat the light emits, but it only measures the brightness. To be more specific lux meter can only measure the brightness based on what humans can see.
Even if it doesn’t measure the heat, this can still be an accurate reference for you to know what would work best with your plants. Here is a guide chart you can check:
15,000 Lux to 70,000 Lux
35,000 Lux to 35,000 Lux
Clones and seedlings
While you can already have this during seeding or germinating, the best time for you to really reap the effects of LED grow lights is during the flowering and vegetative stage.
Remember that this shouldn’t be something to miss when growing plants indoors!
I hope that you find this very useful when it comes to keeping your plants and crops string and healthy. Have fun growing plants indoors!
Lindsey Hyland grew up in Arizona where she attended University of Arizona’s Controlled Environment Agriculture. She has supplemented her formal education by working on various organic farms, including spending a semester abroad in India.
Growing and/or raising just about anything gets her excited. She is especially passionate about environmental justice and low-tech, sustainable ways to better run small-scale farms and homesteads. Lindsey started Urban Organic Yield to discuss gardening tips and tactics.