How Close Do LED Grow Lights Need To Be

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LED grow lights for indoor plants have many advantages and are getting popular. It is a useful alternative to sunlight, whether for cannabis, orchids, or other fruit and vegetables. But, many are questioning how close do LED grow lights need to be?

LED grow lights need to be within 12 – 30 inches or 1 – 2.5 feet from the top of your plants. You must also adjust when your plants grow taller to ensure consistent distancing. Note that the light wattage, plant types, and other factors will also affect the required distance above plants.

This article shares everything you need to know about the proper distance of LED grow lights from your plants. Let’s dive right in!

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Importance to Ensure Proper Distance of LED Grow Lights

Indoor plants require a good distribution of lights for healthy growth at any growth stage. A LED grow light can provide the necessary light spectrum to each type of plant with proper use. It will result in better lighting conditions for your plants.

Besides, LED grow lights for indoor plants consume lesser power and produce lesser heat. While saving energy, it can better prevent plants burns, though you still need to take good care of the distancing.  

Also, when placed right, the LED grow lights can increase your plant yield within a shorter time when compared to other light sources. 

You should read this article to prevent the most common mistakes when using LED grow lights for indoor plants.

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Deciding Factors for Proper Distance of LED Grow Lights

1. Growth Stage of Your Plant

Within the first 3 weeks, the plant is experiencing the seedling growth phase. You should keep the LED Grow Lights within 24-26 inches above the top of the soil.

After that, the vegetative stage of your plants requires more light to carry out photosynthesis. You’ll have to adjust the LED grow lights to 12 – 24 inches from your indoor plants.

Then, the plants need more intense light to encourage flowering at the flowering stage. They will also grow taller and produce fruits at this phase. Place your LED grow lights within 18 – 24 inches from the top leaves of your plants. If you don’t want your plants to grow too tall, you can retain the height of your LED grow lights.

But, each LED Grow Light manufacturer uses different LED brands, lenses, wattage amounts, etc. You can check with your LED grow light manufacturers for the suggested distance between the LED grow lights and your plants. Some of them also place this information on their website.

Even so, the information by your manufacturers is by estimation only. The proper distance between LED grow lights and your plants might change based on various factors.

Growth PhaseDistance of LED Grow Lights from Plants
Seedling Phase24 – 26 inches
Vegetative Phase12 – 24 inches
Flowering Phase18 – 24 inches
how close do led grow lights need to be

2. Type of Your Plants

The light intensity required differs from plant to plant. It also means that the required distance above plants from your LED grow light is different based on their plant type. 

The flowering plants like tomatoes and orchids need closer lights, about 3 – 13inches distance from your LED grow lights.

The leafy greens like lettuce and spinach and the hydroponics like basil and mint require about 6 – 12 inches from your grow lights. 

On the other hand, you should place your LED grow lights 12 – 24 inches from your foliage houseplants like golden pothos and braided money trees. You can refer to the table below.

Type of PlantsDistance of LED Grow Lights from Plants
Leafy Plants3 – 13 inches
Flowering Plants6 – 12 inches
Hydroponic Plants and Herbs6 – 12 inches
Foliage Houseplants12 – 24 inches

3. Power Wattage of Your LED Grow Lights

You should also check for the power wattages of your LED grow lights. 

If the light power is very strong, you can place your LED grow lights a few inches further from your plants. In contrast, put the lower-wattage LED grow lights a few inches nearer to your indoor plants.

You can take a reference on the table below:

Wattage Distance of LED Grow Lights from the Plant (Inch)
200 – 39912 – 20 inches
400 – 59920 – 27 inches
600 – 79930 – 38 inches
800 – 99932 – 42 inches
1,000 & above36 – 46 inches
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4. Light Intensity of Your LED Grow Lights

You must know the number of lights your plants require and receive. 

To determine the light intensity, you can enquire your LED grow lights manufacturers. They could share the measurement of light intensity at different heights above plants for you. 

Or, you can also buy a PAR or lux meter to measure. These meters will tell the amount of PAR or lux your plants received at a certain distance from your LED grow lights. 

Then, convert the number of PAR or lux to obtain your light intensity number in umol/second. You can refer below to the number of lights required by cannabis plants at different growth phases. 

Growth PhaseLight Required
Seedling Phase200 – 300 umol/second
Vegetative Phase receiving 18 hours of lights306 – 617 umol/second
Flowering Phase receiving 12 hours of lights460 – 925 umol/second

You can retain the LED grow lights distance above plants tor plants that get light intensity within the range stated above. You should move the LED grow lights nearer to your plants if the light intensity is below the listed ranges. In comparison, you’ll need to move the LED grow lights further for the plants that receive light intensity above the range listed.

5. Dimmability of Your LED Grow Lights 

You do not have to move the dimmable LED grow lights. In this case, you can dim the lights using a knob or a screw on the ballasts.

Use a lux meter to measure and calculate the light intensity amount. Then, check if your plants receive the required lights and adjust accordingly. 

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What is the Inverse Square Law?

Inverse-square law is a formula or law in physics regarding plants and lights. This law tells the light intensity of your LED grow lights at a certain distance above your indoor plants. You can then decide whether to place your LED grow lights nearer or further from your indoor plants.

According to the inverse square law, when the distance between the indoor plant and the light doubles, the area covered by your LED grow light increases. At the same time, the light intensity will reduce to 25% of the original intensity.

Let’s take an example. When the LED grow light is at 1meter from the plant, the light intensity is 100%. If you move the light further to 2 meters from the plants, the LED grow light will generate only 25% light intensity. When the distance between the light and the plants is 4 meters, the light intensity will become 6.25%, which is 25% to the light intensity at 2meters. 

You can use the formulae below to calculate:

Intensity = Light Output/Distance²

inverse square law

Sign to Adjust the Distance of LED Grow Lights for Indoor Plants.

You should make adjustments to ensure the proper distance of LED grow lights in the following situations:

Too Far From Plants

If you place the LED grow lights too far from your plants, your indoor plants will overstretch to get sufficient lights. Also, they will have long internodes, which means longer stems in between the leaves if your plants are not getting enough lights

Not only that, the leaves might be smaller than usual, and the stem might be pale-green. Some of the lower leaves might even become yellow and drop off. 

If you notice such a situation, you should hang the LED lights nearer to the plants.

Too Close to The Plants

In contrast, your plants will be heat stressed, overheat or burn when the LED grow lights are too close to them. The leaves will tend to curl upwards or turn crisp. Besides, your plants might appear to be discolored or bleached. 

In this case, you’ll need to move the LED grow lights further from your plants to prevent irregular or stunted growth. 

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Final Thoughts

To conclude, the distance between LED grow lights and your plants differs due to many factors. You should study the critical factors that affect, as well as signals to adjust your lights. 

It is vital that you choose a genuine brand and a trusted manufacturer when buying a LED grow light. You can refer to these articles to learn How to Choose an LED Grow Light and Top 11 Things to Consider When Purchasing LED Grow Light

Being an experienced LED light manufacturer with premium quality LED grow lights, Darkless LED is the name you can trust. Talk to our customer service team to learn more about LED grow lights!

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