How to Use LED Grow Lights for Indoor Plants

Indoor seedlings growing under LED grow lights

Whether you’re raising a rare species flower or simply growing herbs and greens for the dinner table, LED grow lights can help you cultivate a variety of plants indoors.

Growing indoors gives you several advantages over outdoor gardening. The most obvious is that you can better control the temperature. Most plants will have a narrow range of temperatures under which they will produce blooms or fruit.

Another factor you can control in an indoor growing environment is the humidity level. While some plants love moist, humid air, others are prone to disease under those same conditions. Alternatively, many succulents and cacti prefer a dry environment, which you can provide in an air-conditioned space.

Outdoor gardening, however, has one distinct advantage over indoor gardening, and that’s a surplus of the necessary sunlight that so many plants require to thrive.

Fortunately, LED grow lights can provide all the light your plants need -- efficiently and inexpensively.

Indoor houseplants growing under desk clip on LED grow lights

What Are LED Grow Lights?

LED (light emitting diode) grow lights offer an energy-efficient option for indoor gardening. They’re made using two different types of semiconductors within a chip, one with a negative charge (electrons), and the other with a positive charge (holes). The two are separated by an “energy gap.”

When electricity is applied to the chip, electrons are stimulated, and when one falls into one of the holes, recombination occurs, and this creates a photon of light. This is how LED lights work.

LED grow lights are specially designed to emit the right kind of light for growing plants indoors.

Using LED Indoor Plant Lights

But before you run out and buy some cheap LED bulbs, you need to understand how they work to nurture your plants.

You’ll need to know which type of LED grow lights you need for different plant types. And depending on the species and your gardening goals, you’ll need to know how many hours of light they’ll need.

Most importantly, you’ll need to understand how the color of your LED grow light affects your plants.

Sunlight contains the right spectrum -- or colors -- of light for healthy plants. When you see a rainbow created by a rainstorm, the sun’s light is broken up into various colors. This range of colors is called the light spectrum, and the colors you see are those visible to the human eye.

Light is measured in terms of electromagnetic radiation. The full spectrum of light also includes non-visible light, like ultraviolet light (<400 nanometers) and infrared (>400 nanometers). It even includes microwaves and radio waves.

These colors represent different wavelengths of the light --- and each color in the visible spectrum has a different wavelength, from 700 nanometers to 400 nanometers.

What Is the Best Color Spectrum for Plants?

One of the critical aspects of growing plants indoors is the color of the light used. The colors we see on either end of the spectrum -- red and blue -- affect plant growth the most. And each color affects your plants in diverse ways.

Plants react differently to distinct colors of the light spectrum, and to make matters more confusing, they need a different color of light depending on their stage of development.

In short, plants need a different color of light when they’re growing from seed than when they’re ready to bloom.

Plants respond to the visible spectrum -- between 400 and 700 nanometers – because this range stimulates photosynthesis.

Plants absorb more light in the red and blue spectrum, reflecting more green and yellow light, which accounts for their lush green coloring.

So, any grow light needs to supply adequate light in the red and blue wavelengths.

Starting seedlings indoor using LED grow lamps

Red Light

Red light has a wavelength that is longer than other colors, and for plants the most critical of these are from 640 to 680 nanometers.

Red light stimulates the growth of stems and flowers and boosts fruit production. It also aides in chlorophyll production.

Indoor gardeners need to use light in the red band of the light spectrum if they want their plants to bloom. Red light is also necessary for growing vegetables indoors.

Blue Light

Light in the blue part of the spectrum is the most critical color for your plants. Blue light in the 430 to 450 nanometer range is the most important. Along with stimulating photosynthesis, blue light is the best color spectrum for vegetative growth and developing strong roots.

Many indoor gardeners use blue light exclusively for starting seedlings, when they are in their early stages of root and stem growth.

Yellow and Green Light

While not as critical to development as blue and red light, plants do use green and yellow light for photosynthesis.

UV Light

While overexposure to UV light in the shorter range of wavelengths can stress plants, UV closer to the visible spectrum can often increase the yield in many herbs, like sweet basil and Chinese licorice.

It’s especially important for increasing the amount of volatile oils in plants intended for use in making essential oils, such as spearmint and peppermint. These volatile oils also give culinary herb their distinctive flavor in cooking.

Infrared Light

Infrared light – sometimes called “far red light,” plays a special role in plant development. Plants use phytochromes to absorb red and infrared light, and these photoreceptors regulate the plant’s circadian cycles as well as the timing of seed germination, dormancy, and flowering.

Some plants respond to infrared light by flowering and fruit production, including popular vegetables like tomatoes and cucumbers. Gardeners who cultivate flowering plants indoors, such as African violets and orchids, should look for LED grow lights that produce infrared light. 

visible spectrum colors

What Is the Best Light Intensity for Plants?

You may assume that the more intense your LED grow lights are, the better they are for your indoor plants. That’s only partially true.

Light intensity is measured as “PAR” -- which stands for Photosynthetic Active Radiation. In short, this measurement expresses the amount of light your grow lights give off that your plants can actually use. This helps identify which grow lights produce light in the right wavelengths of the spectrum for the best results.

You can determine this by using a simple PAR meter. Best of all, you can check various areas in your indoor garden setup to ensure that the light is well distributed.

So, while you may think that intensity is a critical factor, what you want to look for is quality of light first. Intensity is easy to adjust by moving your LED grow lights closer or further away from your plants.

The Advantages of Using LED Grow Lights

Horticulturists have been growing plants indoors for many years using fluorescent, HID, and incandescent lighting. But recent advancements in LED technology have made them the go-to for many indoor gardeners.

They offer distinct advantages to more old-fashioned lighting systems.

First of all, they’re extremely durable, offering years of use for a small investment. LED grow lights offer 50,000 hours -- about 12 years of use when operated for 12 hours a day. While fluorescent tubes offer 20,000 hours lifespan at best, their quality for use in gardening applications begins to degrade after only one year.

LED lights are cooler. They emit much less heat than conventional lighting. That means you can place them closer to your plant’s leaves without fear of scorching.

It also means that there is less risk of accidental fire, and less need for increased ventilation. Many people who garden indoors with artificial light find that it can significantly increase the heat load of their homes. This means a bigger strain on your A/C system and your wallet.

And finally, one of the most popular advantages of using LED grow lights is that they use so much less electricity than other types. According to the U.S. Department of Energy, LEDs use 75 percent less energy and last 25 times longer than incandescent lights.

pot of plant in room white background

Choosing the Right LED Grow Lights

Now that you’re ready to start your indoor garden, it’s time to choose the right LED grow lights. You now know that providing your plants with plenty of blue and red light is crucial. You also know that white, infrared, and UV light also has an impact on your indoor garden production.

Here are some other tips to make choosing the right Brite Labs LED grow lights for your indoor plants.

How Long Should I Use My LED Grow Lights?

Most plants require long hours of sunlight to flower and bloom, which is why summer is the best time for growing vegetables outdoors.

Exposing your plants to 12 hours of light a day is recommended. But, remember that your plants also need some dark time to rest. Look for LED grow lights with convenient timers to regulate light exposure.

How Far from My Plants Should I Place My LED Grow Lights?

LED grows lights should be placed from 14 to 30 inches above the plants. One of the biggest advantages of using LEDs is that they put off so little heat. So, you can place them close to your plants without worrying about burning them.

What Color LED Grow Lights Should I Get?

Look for LED grow lights that offer adjustable colors. When you’re first starting your seedlings, you may want to use only blue light to give them a quick jump start. Once they’ve matured, you can add red light to encourage them to bloom and provide fruit.

Finally, in order to make placing your LED grow lights fast and easy, look for lights that offer adjustable stands and hanging kits.

Happy Gardening -- Indoors

There’s nothing quite like enjoying a home-cooked meal featuring produce from your own garden. And with the right lighting, you can grow vegetables year-round, despite the season.

You may have thought about growing your own salad greens, herbs, and other fresh vegetables indoors. Luckily, technology has finally caught up with your dreams. LED grow lights are perfect for cultivating plants anywhere and at any time.

Best of all, they’re affordable, durable, and safe.