How Far Should LED Grow Lights Be From Plants?

Growing plants indoors can make your home beautiful, but you can’t compromise on the amount of light that plants need.

Using indoor grow lights is one way to combat this issue.

But, have you ever wondered how far LED grow lights should be from plants? 

A good rule of thumb is to keep LED grow lights 12–30 inches above your plants.

The perfect distance between your plants and the LED lights will depend on the type of light, wattage, and plant growth stage. If you choose a powerful one, such as a 600–800W, the top leaves should be 24–30 inches away from the LED grow light. 

Keep reading for more information on the optimal distance between your grow lights and plants in all growth stages. And how to calculate how high your grow lights should be above your plants.

Here we will also discuss the 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 also apply this information to HPS, LED T5, or CFL lighting technology.

How To Determine How Far Should LED Grow Lights Be From Plants

Light, whether natural or artificial, helps plants go through the process of photosynthesis. This is the process plants use to convert sunlight into energy. They produce glucose from the carbon dioxide, water, and light that they receive.

What’s more, effectively placing your grow lights can increase yields, exponentially help plant growth, and give your plants a long and happy life.

However, as with most things, not getting enough light can be detrimental, but more is not always better.

So, when it comes to light, we have to make sure that our plants are getting just the right amount of light.

There are different grow lights that you can use for indoor gardening. Some growers use fluorescent bulbs, HPS lights, and LED grow lights.

Most amateur indoor gardeners choose LED grow lights because they have the red and blue shades that plants in different growth stages need to thrive.

The truth is, there could be multiple answers to this question of how close to keep grow lights to plants, but there is a general rule you can follow called the hand test.

This is when you put your hand under your grow lights for 30 seconds at different heights (keeping in mind that you will place you’re the top of your plants where your hand is).

When the heat becomes too much for you to bear, it is too close. You want to place the plants close enough that they feel the heat but not too close that it will burn them.

Too much light or a light intensity that is too strong could damage your plants and even kill them.

While the hand test does work, there are still different types of grow lights you can use when setting up an indoor garden.

Depending on the light you choose, the specific distance from the plants will vary.

Why do Different Grow Lights Need to be Hung at Different Heights?

There are different grow lights that you can choose from to deliver the light your plants need. However, not all grow lights are created equal.

Each light needs to be hung differently to avoid over and underexposure of your plants to the light. This is because different lights produce varying intensities and light spectrums.

LED grow light distance from the plant

Unlike with MH and HPS grow lights, there is no “standard” distance to keep each LED grow light. The distance needed between an LED and the top of the plants varies quite a bit from model to model and from manufacturer to manufacturer.

Many things can affect the optimal distance from plants, including the individual size of each LED bulb and the way the manufacturer uses lenses to reflect light downwards on your plants.

However, with the right distance, you’ll be able to grow strong and healthy plants as this won’t burn them out.

When plants are overexposed and grow too close to their light source, you’ll see them start to look bleached with yellow spots all over their leaves. Overexposure can also cause nutrient deficiencies.

LED light distance from seedling?

For seedlings, the top leaves should be 24-30 inches away from the LED grow light. This is because seedlings are more likely to dry out.

Keeping lights farther away will prevent this from happening while still providing the light they need to grow and become established.

Vegetative Stages

For vegetative stages, you can move the light closer because they are more established. Keep the top leaves about 18–24 inches away from the LED grow light.

They need more light for photosynthesis processes and are less likely to be damaged by light.

Flowering Stages

For flowering stages, the top leaves should be 12-24 inches away from the LED grow light. They are able to be closer to the lights because they need more energy to produce their flowers and grow fruit.

LED grow light distance chart

However, as mentioned above, unlike other types of grow lights (such as regular LED lights), it could be a bit complicated to know how far your LED grow lights should be from your plants.

Here is a LED grow light distance chart focusing on the various wattages of LED grow lights:

LED grow lights Wattage	Distance from Plants
1 watt	16 inches or 30 cm from your plan
3-5watts	20 inches or 30 cm from your plants
6-10watts	21 inches or 53 cm away from your plants
200 watts	12 to 20 inches away from your plants
250- 400watts	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

HID Light Spacing: How close is too close?

HID, or High-Intensity Discharge, grow lights can produce a strong amount of heat when turned on.

Therefore, if you choose to use these as your light source, they should be placed far enough away from your plants.

In the seedling stage, keep the light at least 6 inches away from the plant. If it starts to wilt, move the light a bit farther away.

The seedlings are fragile and not as resilient as more established plants so you need to be careful when placing grow lights.

In the vegetative and flowering stages, the distance from the plant will depend on the wattage of the light bulb.

Here’s a suggested guide on how far you should be placing the HID grow lights away from your plants based on the wattage:

Wattage	Suggested Distance
1000W	Hang 19-26 inches above the canopy (top of the plant)
600W	Hang 12-18 inches above the canopy (top of the plant
400W	Hang 9-12 inches above the canopy (top of the plant)
250W	Hang 6-8 inches above the canopy (top of the plant)

Even if HID grow lights can produce intense heat, it doesn’t mean that they 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, including T5s, CFLs, and T12s. That means that there will be variations when it comes to distances from plants.

As long as it’s not too hot, you can’t give your plants too much light with these types of grow lights.

Fluorescent lights like T5s and CFLs typically can’t produce enough light to burn plants the way more powerful lights can.

So, the best thing to do is to keep the lights as close as possible so long as the distance passes the “hand test.”

Just make sure to give enough extra space for fast-growing plants because the heat can hurt them if they grow into the lights!

For seedlings, lights should be placed 5–6 inches above the top of the leaves.

This is because seedlings need a higher intensity of light.

For vegetative and flowering stages, lights should be placed about 12 inches above the top of the leaves.

For the best results with T5s and CFLs, try to keep the lights as close as possible and adjust them often to prevent the plants from growing into the light.

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 grow lights are specific HID grow lights that seem to work the best for indoor gardeners (especially for growing fruits and vegetables).

These two usually come together in kits as they both help in providing the right light spectrum to your plants.

Metal halides provide light in the blue spectrum, which is good for the vegetative stages, while the HPS (High-Pressure Sodium) lights are ideal for the flowering stage.[2]

Metal Halide lights are well-suited to the vegetative stage but they are less electrically efficient compared to HPS.

HPS lights are suitable for both the vegetative and flowering stages of plant growth, and the light they give off encourages plants to quickly grow tall and produce many flowers.

Despite these differences, MH and HPS bulbs need to be kept about the same distance away from your plants.

For seedlings, keep the lights at least 8 inches away from the top leaves. If the plant starts to dry out, move the light a bit farther away.

For vegetative and flowering stages, the distance the lights should be from the plant depends on the wattage of the bulb.

Wattage	Suggested Distance
150 W	8 to 12 inches
250 W	10 to 14 inches
400 W	12 to 19 inches
600 W	14 to 25 inches
1000 W	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, the lights will be too close to the plants and will potentially burn them.

In addition to the wattage, it’s important to realize that older bulbs stop giving off as much light over time, so new MH/HPS bulbs generally need to be kept further away and older bulbs should be kept closer than the normal recommendations.

If you’re using new bulbs, never start with the closest suggested distance on the chart, and only move lights closer if your plants are stretching toward the light (getting tall and lanky).

In general, MH bulbs need to be replaced about once a year, while HPS grow lights last a bit longer, up to 2 years.

Older HID bulbs give off less light and more heat, so in addition to keeping the right distance, make sure you’re aware of the age of your bulbs.

How to measure how much light your plants are getting

Keep in mind that grow lights can wilt and burn your plants, even if they don’t really produce much heat. Monitor your plant and see how it responds to the light.

This could be a trial-and-error process when it comes to perfecting the distance between your grow lights and your plants, so be patient and remain alert to see how your plants are doing.

Lux Meter to Measure Light Levels in Your Grow Room

A lux meter is used to measure brightness levels. This could help you get 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 that the light emits, but only the brightness. To be more specific, a lux meter can only measure brightness based on what humans can see.

Even if it doesn’t measure the heat, this can still be an accurate reference for knowing what works best for your plants. Here is a guide chart you can check:

Stage	Lux Measure
Vegetative	15,000 Lux to 70,000 Lux
Flowering	35,000 Lux to 35,000 Lux
Clones and seedlings	5,000–7,000 Lux

FAQ

Conclusion

Regardless of the grow light you use, the distance from plants will vary and it will take some experimentation.

If your plants start to wilt, move the light farther away. If the plant starts to stretch towards the light, move the light a bit closer.

As of today, LED grow lights are widely used for indoor gardening, mainly because of their spectrum capability. It is less expensive and runs longer than other types of grow lights.

While you can already have this during seeding or germinating, the best time for you to really reap the benefits of LED grow lights is during the flowering and vegetative stages.

References