The Complete Guide to Light Spectrum and Wavelengths

The Complete Guide to Light Spectrum and Wavelengths

As more people are turning their homes into green spaces, indoor gardening has shot up in popularity, making LED grow lights an essential tool for anyone wanting lush, healthy plants. These special lights mimic the sun’s spectrum, letting you grow a variety of plants indoors no matter the season.

But with all the different LED grow lights out there, figuring out which one is right for your green buddies can feel like a science project. That’s where this guide comes in. We’re here to simplify all that spectrum science for you, making it easy to pick the right light for your plants so you can have a flourishing indoor garden all year round.

What is a Light Spectrum?

The light spectrum might sound like a complicated term, but it's actually based on a simple concept that's pretty cool once you understand it. Imagine light is made up of tiny particles called photons. When you flip on a light switch, what you're really doing is sending out a bunch of these photons into the room.

These photons are like the messengers of color, and the message they carry depends on their wavelength. Shorter wavelengths, around 450-490 nanometers, are like the blue birds of the light world, delivering blue light. On the flip side, longer wavelengths ranging from 635-700 nanometers are the red doves, bringing red light to our eyes.

What's interesting is that light usually isn't just one color. It's not often you'll find photons all lined up, being exactly the same. Instead, light is more like a party mix of different wavelengths. This mix – how many of each kind of "color bird" there are and how they're arranged – makes up light's spectrum. And just like at any good party, the variety is what makes it beautiful. When we look at the light, we see this whole spectrum, even though our eyes usually pick it up as one main color.

What Are the 7 Spectrums of Light?

What Are the 7 Spectrums of Light?

Light spans across a beautiful array of colors which we can arrange based on their wavelength, from the longest to the shortest. This sequence goes as follows: red, orange, yellow, green, blue, indigo, and violet. The visible light spectrum is like a rainbow that includes many different colors, each with its own special wavelength.

But not everyone sees this rainbow the same way. Some people can catch glimpses of colors stretching into the ultraviolet and infrared areas, which are usually out of sight for many of us. This means that the edges of what we call "visible light" aren't exactly the same for everyone.

  • Fun Fact: Just because you might see really far into the red end doesn't mean you'll see equally far into the violet end, and vice versa.
  • DIY Test: You can explore this yourself with a simple experiment. All you need is a prism and a sheet of paper. Shine a white light through the prism to spread out a mini rainbow onto the paper. Try to mark where the colors start and end. When you compare your rainbow with others, you might notice differences in size!


What Is the Order of the Wavelengths of the Light Spectrum?


  • Indigo: 420–440 nm - Mysterious and deep, indigo offers a wavelength that bridges the gap between blue's coolness and violet's intensity.
  • Violet: 380–450 nm - It's the superhero of the spectrum, having the shortest wavelength but the most energy.
  • Blue: 450–490 nm - Sits comfortably in the middle, giving off those calm, blue vibes.
  • Green: 495–570 nm - Green lights up our world right in the spectrum’s heart.
  • Yellow: 570–590 nm - Bright and sunny, yellow shines with a medium wavelength.
  • Orange: 590–620 nm - Orange glows a bit longer, stretching out in the spectrum.
  • Red: 620–750 nm - The chill of the group, red has the longest wavelength but keeps its energy low.


Each color light has its own wavelength, from short to long, changing from violet to red. This whole colorful world of light helps our plants grow, lets us see, and makes rainbows possible.

How Does a Light's Spectrum Influence the Growth of Plants?

How Does a Light's Spectrum Influence the Growth of Plants?

Just like how we need a variety of foods in our diet to grow strong and healthy, plants need a variety of light to grow properly. The light that plants use to do photosynthesis is called Photosynthetically Active Radiation (PAR), and it includes light from 400 to 700 nanometers. But, not all light is useful to plants. Light outside of this range just doesn't help the plant grow.

Different colors of light, or wavelengths, do different things for a plant. For instance, red light helps the plant grow bigger, but too much red light makes the plant tall and skinny with thin leaves. That's why it's important for plants to get a "full-spectrum" light, which is like a mix of all the different kinds of light they need.

Depending on the stage of growth the plant is in, changing up the light color can be really helpful. Adding more blue light when the plant is just a baby (or in its vegetative stage) makes it grow short and stout, which is good because then all parts of the plant get enough light. When it's time for the plant to flower, more red light speeds up growth and makes the plant bigger, just like it would happen in nature when the seasons change.

That's why using lights that give off a full spectrum of colors, like the sun does, is the best idea for growing healthy plants. These kinds of lights make sure the plants get all the light colors they need at every stage, just like they would if they were growing outside.

How Different Colors of Light Affect Plant Growth


Blue Light and Plant Growth

Blue Light and Plant Growth

Blue light, which has wavelengths between about 450 to 490 nanometers, is super important for the growth and health of plants. It's like the energy drink for plants, making them do a bunch of important stuff like making more chlorophyll, which is crucial for their food-making process. It also tells plants when and how to grow their leaves and roots, making sure they get big and strong. Plus, it's got a big job in helping leaves open up and take in carbon dioxide and letting out oxygen and water vapor, which is part of why we get to breathe fresh air.

When plants get blue light, it makes these tiny things called auxins go to work. Auxins are like the plant's growth managers, telling cells to stretch out or divide to make new parts of the plant. They hang out at the tips of the plant and move to the side that's not getting much light, telling the plant to grow towards the light. This helps the plant bend and reach for the sunshine, ensuring it gets the energy it needs to keep growing.

Even cooler, researchers found out that plants grown under blue light turn out way different than those under other kinds of light. For instance, lettuce seedlings under blue light ended up having bigger and greener leaves than those grown under red or white light. They also got taller and leaner, which shows just how much blue light can do for a plant's growth.

Green Light and Plant Growth

Green Light and Plant Growth

While often overlooked, green light, with wavelengths between 495 to 570 nanometers, plays an important role in plant growth and health. Previously underestimated, especially by proponents of purple grow lights, green light has been proven to support photosynthesis, albeit less efficiently than the red and blue wavelengths.

This light color affects various plant physiological processes, including the regulation of plant architecture—promoting slender, taller shoot growth while slightly inhibiting root expansion. This characteristic benefits plants in systems with spatial constraints, like hydroponics. Additionally, green light can penetrate deeper into the plant canopy, energizing lower leaves and promoting overall biomass accumulation.

It also influences the timing of flowering by affecting specific plant hormones and stimulates the production of secondary metabolites, such as flavonoids and carotenoids. These compounds don’t directly boost growth but are vital for the plant’s defense and stress response mechanisms, showcasing green light's multifaceted contributions to plant development.

Yellow Light and Plant Growth

Yellow Light and Plant Growth

Yellow light, found in the 570-590 nm range, isn't the star of the show when it comes to photosynthesis, but it's got a role to play in plant growth. Even though it doesn’t do much on its own, yellow light teams up with other light colors to help plants in cool ways, for example, mixing yellow light with blue light can make roots in some tiny seedlings stretch out more. Or, when you add it to red light, plants like lettuce can make more of the stuff that helps them do photosynthesis better.

Also, yellow light seems to have a secret power. When plants are stressed out, like when there's not enough water, or there's too much salt in the soil, yellow light can help them fight back. Tomato plants getting some yellow light could handle salty soil better than those that didn't. Scientists are still trying to figure out all the ways yellow light affects plants, but it looks like it's pretty important for keeping plants healthy, especially when growing them for food or in tough conditions.

Orange Light and Plant Growth

Orange Light and Plant Growth

Orange light, shining in at wavelengths between 590 to 620 nanometers, might not grab the headlines like the red or blue light does, but it's still pretty cool for helping plants grow strong and healthy. This kind of light is a bit of an unsung hero, kind of like the bass player in a band. You might not always notice it, but it adds something special to the mix that helps everything come together.

For instance, some studies have discovered that when you mix in some orange light with the red and blue, plants like lettuce can end up taller, with more leaves, and weigh more too. Tomatoes also seem to love a bit of orange light, producing more flowers and fruits that are ready to eat.

Even though scientists are still figuring out all the magic behind orange light, it's clear that it has its own important role in making plants happy and healthy, especially when it's part of a full light spectrum team.

Red Light and Plant Growth

Red Light and Plant Growth

Red light is super important for plants because it really gets photosynthesis and growth going. Think of red light as the coach that gets the team moving. Around 620 to 750 nanometers in wavelength, this light is grabbed by a special team player in plants called phytochrome. Phytochrome can change its game depending on whether it's soaking up more red or far-red light, which is pretty cool. When plants get red light, it's like flipping a switch that wakes up a bunch of genes that do everything from starting a seed's growing process to pushing flowers to bloom and encouraging roots to stretch out.

One of the big deals with red light is it tells plants when to wake up and start growing – kind of like an alarm clock that also waters them at the same time, thanks to needing water to kick off germination. With red light, plants also stretch out more, reaching up and out to get as much light as they can, making sure they don't get stuck in the shade.

For those playing the long game, red light tells plants when to flower by firing up some special growth hormones. Plus, it helps them fight stress, like too much sun or heat, by beefing up their internal shields with antioxidants. And if plants find themselves shaded by others, red light helps them stretch even more, avoiding the shade and reaching for the sun. This bit about stretching in the shade is a move to make sure they're getting enough light, even when it's a bit crowded.

Are Ultraviolet Light and Infrared Light Good For Plants?

Both ultraviolet (UV) and infrared (IR) light play significant roles in plant growth, each offering unique benefits and drawbacks. Understanding their effects can help in optimizing plant health and yield.

Ultraviolet Light (UV)


  • In moderate doses, it stimulates the production of protective secondary metabolites like flavonoids and anthocyanins, enhancing plant defense against UV damage.
  • Can improve the nutritional and medicinal value of plants.



  • High levels can damage plant tissues, leading to DNA mutations and reduced photosynthesis.
  • Increased risk of diseases, pests, and, potentially, plant death in extreme cases.


Infrared Light (IR)


  • Promotes stem growth and flowering through its thermal effect.
  • Stimulates metabolic processes, improving plant growth.
  • Influences stomatal regulation, aiding in water loss and gas exchange.
  • Can enhance leaf size, thickness, and impact hormone production, benefiting overall plant development.



  • Excessive IR can overheat plant cells, causing wilting or burning.


The Spectrum of LED Grow Lights

The Spectrum of LED Grow Lights

When LED grow lights first hit the market, people nicknamed them “smurf” lights because they only used red and blue lights. Scientists thought these colors were the best since plant cells soak them up more than green light. But guess what? Adding green light to these LED lights turned out to be a game-changer.

New studies found that throwing some green into the mix actually helps plants grow more. This is because green light can sneak deeper into the leafy parts that red and blue light can't reach, helping more of the plant get in on the photosynthesis action. More light getting to more parts of the plant means it can make more food for itself, and that leads to bigger harvests. Plus, green light helps plants grow up with stronger bodies.

Now, LED grow lights are not just about red and blue; modern ones shine in a white, full-spectrum glow. This new light setup is so good, it can even outgrow the old-school High-Pressure Sodium (HPS) lamps that used to be the big deal for growing plants.

Frequently Asked Questions


How does wavelength of light affect plant growth?

The wavelength of light from 400 to 520 nanometers, which includes violet, blue, and green light, really pushes plants to grow their leaves and stems. On the flip side, far-red and infrared light, ranging from 720 to 1000 nanometers, helps seeds start to sprout but isn't absorbed much by the plant.

What light spectrum is best for growing plants?

The best light spectrum for growing plants includes 630-660 nm light, which is in the red light range. This red light is super important because it helps seeds start to grow, makes stems get taller, and leaves get bigger. It also tells plants when it's time to grow and when it's time to flower.

How does light color spectrum affects the growth of a plant?

Different colors of light can really change how a plant grows. Blue light is awesome for getting a plant to grow leaves. But when you mix red light with blue, it's like a secret message that tells the plant it's time to start making flowers. Knowing this is super important since we all need plants for food!

How do plants use different wavelengths of light?

Plants use light to do photosynthesis, which is like their way of eating. Chlorophyll a, which all plants have, grabs sunlight in the violet-blue and reddish orange-red wavelengths but doesn't hold onto green and yellow-green light - that's why plants look green to us. This light grabs electrons and gives plants the energy to turn carbon dioxide and water into food and oxygen.


Understanding the spectrum of light and how different wavelengths affect plant growth is like discovering a secret language that helps us talk to plants. By tuning into this language, we can provide our leafy friends exactly what they need to thrive. From the deep blues that encourage lush leaves to the vibrant reds that signal it's time to flower, every color offers something special.

Ready to see your plants thrive like never before? Visit our website to explore the world of LED grow lights crafted just for your gardening success.

And if you're hungry for more juicy tips on making your plants happier, check out our blog. Any questions or need advice? Feel free to contact us. We're here to help you grow your green thumb!

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