How Do You Use LED Grow Lights for Plants?

If you live in a region where sunlight is sparse, LED grow lights are an optimal solution for encouraging photosynthesis in your plants. If want to learn how to use LED grow lights for plants this article will explain just that.

To use LED grow lights for plants, you should ensure the lights you choose are an appropriate color spectrum (with blue and red light). Grow lights should be positioned on average at least 12 inches from a plant, but this can vary, as can how many hours of light a houseplant needs. 

This guide to grow lights will tell you everything you need to know about using artificial lights for your indoor garden. I’ll discuss how to choose the best LED grow lights for your plants, where to position the lights, and how long to leave them on. 

Let’s get started! 

Choosing the Right LED Grow Lights for Your Plants 

I’ve discussed the uses and the differences between regular LED lights and LED grow lights before but regular LEDs and LED grow lights should not be used interchangeably except on a short-term basis.

Regular LED lights just don’t have the wavelength width that plants need while LED grow lights to provide your plants with optimal artificial light that encourages the best photosynthesis throughout a plants growth stages.

Knowing that information makes it obvious you’ll want to use LED grow lights. But how do you choose the right LED grow lights?

Here are the main points to consider when choosing the correct LED grow lights for your plants.

Color Spectrum

Of all the considerations to make when shopping for LED grow lights, the color spectrum is undoubtedly at the top of the list.

You must select lights with a varied color spectrum to ensure that ALL of your plant’s needs are accommodated.

Here are the types of light that should be represented on the color spectrum of your LED grow lights. 

Blue Light

One on end of the color spectrum is blue light, which is integral to the health of your plants. 

The color can activate photosynthesis in plants, which is how plants produce energy and grow. Through photosynthesis, you can ensure your houseplant has sturdy roots and produces more foliage. 

The best blue light range for indoor plants is between 430 and 450 nanometers. 

Red Light

The other end of the color spectrum is red, and this light color is equally as important. 

The long wavelength of red light allows plants to grow fruit, flowers, and stems. Of course, your plant won’t magically produce fruit if it doesn’t usually, but its foliage will look healthy.

Further, red in LED grow lights is crucial in upping the rate of chlorophyll that a houseplant makes. Chlorophyll is how a plant has its trademark green pigment! 

Your LED grow lights should produce red light between 640 and 680 nanometers. 

Green/Yellow Light

Many people that care for plants who are shopping for LED grow lights stop when they find an LED grow light that emits red and blue light. I say keep going and check that the light produces green and yellow wavelengths as well.

Are the green and yellow light colors as crucial in an artificial grow light compared to red and blue light? No, but they do help, especially when it comes to photosynthesis. 

Electromagnetic Spectrum

The electromagnetic spectrum refers to electromagnetic radiation wavelengths. LED grow lights should include both infrared and UV light, and here’s why. 

Infrared Light

Infrared light is radiant energy with extended wavelengths that serves a unique purpose. 

Plants have photoreceptors known as phytochromes, which are also present in fungi and bacteria. The phytochromes are the plant’s way of detecting a source of light. 

A plant can also rely on its phytochromes to absorb light sources, including both infrared light and red light.

Exposure to infrared light via an LED grow light can increase a plant’s production of fruit or lead to more flowers. Infrared light is especially crucial for growing healthy orchids, African violets, cucumbers, tomatoes, and other indoor vegetables. 

UV Light 

Ultraviolet or UV light is usually something to be avoided, but some UV light in an artificial grow light can be a good thing when it comes to using artificial light to help grow plants.

That’s especially true the nearer the UV light is to the light spectrum. 

If your plant produces a yield, as is the case with an herb or a vegetable or fruit plant, then UV light can boost that yield.

Which types of plants benefit most from UV light? You’re most likely to get the best results from plants such as peppermint, spearmint, and sweet basil using UV. 

Light Quality

The next consideration for LED grow lights is light quality. 

Grow lights are measured by Photosynthetic Active Radiation or PAR.

  • The higher the PAR, the more usable light through the correct spectrum and wavelength that the LED grow light produces.
  • The lower the PAR, the less light released that a plant can use.

The easiest way to determine the PAR of your LED grow lights is by reading the label on the box the lights came. You can also check the light itself with a PAR meter.

While using PAR meters is outside the scope of this article, I will be explaining how to use a PAR meter to in a future related article.

Light Intensity 

LED grow lights produce light wavelengths and intensity akin to natural sunlight. That doesn’t necessarily mean you want the greatest light intensity available though.

Like too much sunlight can burn your plants, artificial light at too high an intensity can also leave your plants in duress. 

Single Bulb vs. Multiple Bulbs

Next, you should think about the quantity of grow lights you need. Make this decision in conjunction with the size and amount of plants you’re trying to maintain using the artificial sunlight. 

If you have only a few plants, then there may not be the need for an array of grow lights. The light intensity might be too high for so few plants, and that can wilt or possibly burn your plants. 

If your plant is a hanging plant growing in a hanging planter what you can do is attach a single bulb to an S-hook and then angle the single light over and roughly a foot above your plant. 

You can also buy a small lamp, remove the regular light it came with and replace it with an LED grow light bulb and angle the lamp over your plant. I do this all the time with plants on my bedside tables.

If your indoor garden begins to grow, you’ll naturally evolve from using single bulbs to multiple bulb options and even more expansive setups such as a light array. 

Positioning the LED Grow Lights for Plants

If you were using sunlight for your houseplant’s growth, you’d spend quite a while selecting its ideal positioning in a room. For instance, is the easterly-facing window best for your plant, or is the northerly-facing one better?

I’d highly recommend putting as much consideration into selecting the spot where your LED grow lights will go.

If the grow lights are too far away from your plant, your plant will likely become “leggy” from stretching closer towards the artificial light. With the grow lights positioned too far from the plant your plant isn’t reaping its full effects.

Placing a grow light too far from it without any other light source can also cause you to not see as big of a yield or as many bountiful flowers. Your plant also won’t grow as many fruits or vegetables.

LED grow lights, giving off as little heat as they do, shouldn’t scorch your plant’s foliage even if the lights are very close to the plant. 

That said, it’s about finding the best position for your grow lights, not the closest position.

The rule of thumb is that your LED grow lights should be positioned at least 12 inches from your plant. Many indoor gardeners use 14 inches as a baseline, and you can do that as well. 

For roughly 90% of the time you’ll be using LED grow lights for your plants, the furthest distance between the plant and the grow light should be 18 to 30 inches. 

The distance you select will vary based on a handful of factors, including how big your plant is, what species it is, and how many LEDs your grow light setup uses.

Here’s what I recommend. Select a spot for your LED grow lights and leave them there for at least 4 to 5 days, maybe even a week (unless your plant seems like it’s stressed, then change the grow light placement sooner).

Assess how your plant is doing in that span. If you notice that your plant’s foliage is wilted or dry, then your grow lights are probably too close. 

If the leaves seem especially crispy, then you might want to reduce the LED grow light intensity or move the grow light further from your plant.  

Wilting and discoloration such as leaf yellowing or browning can be signs that your plant needs more light. I’d recommend placing the LED grow light a little closer to your plant(s) and monitor it from there. 

What if you don’t notice any change in your plant? Then I’d advise you to leave the lights as they are for now and monitor the plant for a few more days. 

Although grow lights can augment photosynthesis and thus plant growth, none of these are overnight processes. It can be weeks or months before you can compare the yield size and foliage of your plant to how it was before using grow lights. Be patient! 

How Many Hours Should You Use LED Grow Lights for Plants?

Once you’ve got the LED grow light positioned at a proper distance for your plant or plants, the last consideration is how long the LED grow lights will remain on. 

The amount of light a plant needs depends on its maturity, stage and species, but the best practice is that a grow light should be on for between 12 and 16 hours a day for flowering plants. 

For a plant with lush foliage but no flowers, increase the time to 14 to 16 hours while keeping a close watch on the plant.

Whether it’s LED grow lights or any other type of artificial light, no grow light should be on for 24 hours. The sun isn’t out that long, so it goes against the laws of nature and the plants natural internal clock.

Give your plants at least six hours of darkness per day and no more than eight hours. 

During the “lights off” period, your plant will stop photosynthesizing. Although this sounds like a bad thing, it isn’t. Your plant is merely switching from producing energy to using it. 

The time your plant is basking in the glowing artificial light is the period your plant is actively photosynthesizing.

The period of darkness is when the plant can use its energy and similarly grow. 

Ideally, you want to turn the LED grow lights on and off at the same time every day. A consistent schedule of repeated lights-on time and lights-off time plays a very big role in how fast the plant is able to adapt and grow quicker faster.

If the grow light schedule doesn’t work well with your own daily schedule, then I highly recommend buying a timer to automatically turn your LED grow lights on and off for you. This way the plants can quickly count on the consistency and you can begin reaping the rewards of implementing LED grow lights for your plants as soon as possible. 

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