LED Light Spectrum

LED Light Spectrum – Most Important Things to Know

For the vast majority of gardeners, LED grow lights are the first thing they’ll go for, so it doesn’t hurt to know a bit more about the LED light spectrum and how different colors affect plant growth.

That’s why we think it’s a good idea to learn about what LED lighting spectrum is and how you can use this knowledge to your advantage and make sure your plants get the right light from the light color spectrum.

Let’s dive straight in!

What Exactly is Light Spectrum?

What Exactly is Light Spectrum?

Every color our eye can see is actually a specific wavelength that bounces back to the retina. We humans can see a vaster spectrum of colors than most animals, but some animals can see colors such as infrared and UV lights.

Each color you see is set somewhere on the light spectrum, so for example blue color with all its shades is set somewhere between 400 and 525 nanometers.

To put things into perspective, at about 400 nm, you would see a kind of violet-blue color, and on the other end, at 525 nm, you would see cyan.

In spite of plants not having eyes, they can detect color through chlorophyll because certain colors are reflected by chlorophyll and some are “absorbed” by it.

There’s also a light spectrum for plants and it’s measured on the PAR scale. So let’s see what’s that about.

The PAR Scale

PAR is an acronym for Photosynthetically Active Radiation, and no, this doesn’t mean your plants will be exposed to radioactive material, but rather it means which colors on the light spectrum can be used by plants so that they can start the photosynthesis process.

As you already know, photosynthesis is the process of nutrient production from chlorophyll by the absorption of light, however, some colors have better absorption and thus enhance plant growth.

Sunlight, for example, isn’t white light even though you might think it is. Sunlight contains all the colors of the light spectrum mixed together and that’s why it appears white.

Of course, natural light is the best light source for our green friends because it offers natural light and it also has a consistency that plants get used to right from the start.

In conclusion, PAR, the grow light spectrum chart is just a brief explanation of which colors your plants will absorb best.

But what light color is best for plant growth?

Let’s find out.

Best Color Light for Plants

We have a separate article on this topic you’re welcome to check out, so we’ll just briefly explain each color on the light spectrum.

We’ll start from the beginning of the PAR chart and work our way to the last color on the grow light spectrum.

1. Blue Light

Blue light has around 400 to 525 nm wavelength range so this means it sits right at the start of the light spectrum.

Blue light is also known to be the best light for plant growth as it is best absorbed by chlorophyll which means the plants get the most nutrients.

It’s fairly easy to find blue grow lights, especially with LED bulbs so that’s why they’re the most popular choice among gardeners.

2. Green Light

Green light stands at around 500 – 600 nm of wavelength range and even though much of the green light is reflected by the chlorophyll, it still is beneficial to plant growth as it can penetrate thicker foliage and bring light to all parts of the plant.

It’s not so common in grow lights, but some gardeners still like to use it, especially for thicker canopy.

3. Red Light

Red light stands around 630 – 660 nm of wavelength range and as you can see it has a narrower color spectrum than other colors.

Still, red light is an important color for plant development as it benefits foliage and stem growth.

Red LED lights readily available for grow lights, which makes them quite a popular choice.

4. Far Red Light

Far-red, or infrared is an amazing light color for your plants as it speeds up the flowering process and also it produces better foliage.

Although it’s not that easy to find IR LED lights, they’re still a great option especially in the first stage of plant development.

Why Are LED Lights Best for Grow Lights?

Why Are LED Lights Best for Grow Lights?

After our talk about what light spectrum is and which color is best for your plants’ growth, we need to answer the question of why you should use LED grow lights.

Not only are LED lights energy-efficient, but they also produce a broader light spectrum than other light sources which makes them ideal for indoor gardening.

We’ll be explaining all of this briefly, but for now, you need to know that for most plant growing your safest bet is to use LED lights as they’re the most powerful ones and also provide your plants with all the colors of the light spectrum they need for proper development.

LED Light Spectrum

The LED color spectrum is quite broad and you can find LED lights in pretty much any color from the PAR chart so that makes them ideal for gardening.

Of course, LED lights aren’t just used for grow lights, but also for home lights as well so that’s why it’s so easy to find them on the market.

As we already said, the sunlight has all the colors of the light spectrum, which makes it white. As with sunlight, LED lights that appear white are also a combination of colors, mostly red, green, and blue, which make them shine white light.

Add in some yellow, and you have warm white, or, if you add a bit more blue, you get cold white.

With LED lights controlling which color of the light spectrum can be predominant is easy so that you can get the best light color for your plants.

Broad LED Color Spectrum

As we mentioned, LED lights have a broad light spectrum, meaning that they have all the lights the sunlight possesses.

Broad light spectrum, in terms of the spectrum range, is considered to be between 380 and 740 nanometres so it includes all the visible colors our eyes can see. It also contains light which we can’t detect such as UV and IR light, which are also beneficial for plant growth.

So because LED lights are perfect for producing all the colors from the light spectrum, they’re the best for your grow lights.

Since we’re talking about the broad light spectrum, 2 spectrums of light are beneficial for plant growth, and we’ve already mentioned them – UV and IR light.

1. UV Light

UV light seems invisible for us, but the sunlight actually produces a great amount of this light which of course plants do enjoy because it affects vegetative growth.

And there are many articles on the Internet talking about “what is the best color spectrum for vegetative growth?”, but only some of them mention UV lights because with too much UV exposure your plants can get damaged.

However, because LED UV lights aren’t so tough on plants, they won’t do any harm even if you stare at them the whole day.

So again, LED lights are the way to go.

2. IR lights

We’ve already talked about IR lights but let’s just add that this color is great for the flowering period because the IR light rays can penetrate deep into the plant’s chlorophyll meaning it can absorb the whole light source.

So, in conclusion, you should use IR lights during the seedling development, and then use UV lights when the plant matures.

Of course, this method will best serve the purpose of growing cannabis, so you should still see which combination of lights is best for your plants.

Different Plant Type, Different Light Spectrum?

Different Plant Type, Different Light Spectrum?

This is a question commonly asked by both people who are new to gardening and even experienced gardeners as it’s not easy to determine which light color is best for which plant type.

However, we’ll do our best to solve this problem as much as we can.

Plant Type

We don’t just separate plants by their species, genome, or family, but also how much of both chlorophyll types they have.

There are 2 types of chlorophyll all plants have and they are:

  • Chlorophyll a – best absorbs UV, blue and orange-red colors
  • Chlorophyll b – best absorbs blue light

The amount of chlorophyll a or b a plant has depends on its species and even though the amount of both chlorophyll types isn’t drastically different, some plants just grow better under different lights.

One such plant type is cannabis and all cannabis growers insist on growing this plant under either UV or blue light because cannabis has better absorption of colors which sit on the start of the light spectrum.

But which color is best for household plants? Well, we have a solution for that problem as well because by using white LED lights you’re practically using all the colors on the light spectrum so your plants will surely develop without a problem.

Growth improvement is a whole different story, but as both chlorophyll a and chlorophyll b have good blue light absorption, if you want better growth, you should go with blue light.

What About Other Colors?

Other colors of the light spectrum such as green and yellow can do magic with some types of plants.

For example, plants that have denser foliage and thick stocks will benefit a lot from green light as it can be absorbed by the whole plant through chlorophyll so no light is wasted.

Yellow light, as it’s similar to green, has also good absorption because it’s not bounced back by the chlorophyll the same as the green light.

However, yellow light sits somewhere in the middle of the light spectrum, so your plants won’t really enjoy all the benefits blue and red color lights can give them.

Factors Which Affect LED Light Spectrum

Factors Which Affect LED Light Spectrum

Purchasing LED to grow lights that say they have a full LED spectrum sounds like a piece of cake, but actually, things aren’t as easy as they seem.

You can’t just get any LED lights that say “led full spectrum grow light” on the packaging because elements such as the amount of lumen and light intensity also play a huge role in the light spectrum your LED lights produce.

So let’s take a look at each of these elements and see how to get grow lights with LED full spectrum.

1. Amounts of Lumen

Lumen indicates how much your LED lights will emit light. LED lights are made out of small diodes which light up when they’re connected to electric energy.

The more LED bulbs, the more lumen. With more lumen, you get more brightness.

To put things into perspective, LED grow lights typically come in 2500 or 3000 lumens which means they’re much brighter than the LED bulbs you use for your home.

Also, this means that there are more LED diodes that make up the LED grow lamp so it’s able to produce brighter and better light.

The amount of color your plants receive is basically determined by the amount of light your light produces and thus how much of that light color will be absorbed by the chlorophyll.

Sunlight can actually produce 98 000 lumens per 12 meter so if your grow lights can produce just a portion of those lumens, the color absorption of the plants will be enhanced.

2. Light Intensity

Lumens aren’t the only thing that determines how bright your LED grow lights are because light intensity can also affect the LED light spectrum.

Different colors have different light intensities. The blue color is a bit dimmer than the red color. Green is somewhere in the middle, and yellow is similar to green.

The brightest color of the LED light spectrum is white light. And when we’re talking about light intensity we’re talking about the color combination on the white LED spectrum.

As mentioned before, not all white LED light is the same so for example, if the red or green light is a bit more predominate than other colors, your light will appear a bit yellowish, and if there is more blue light used, then it will appear whiter or, as they say, colder.


We hope that this article was both informative and helpful for you and that now you know everything about the LED light spectrum and why you should probably use LED grow lights for your green friends.

Happy gardening!