Why Are LED Grow Lights Purple/Pink?

Why Are LED Grow Lights Purple?

Not all LED grow lights are purple, although, there was a period of time when that was the case. Back then everywhere you looked online most if not all used to be purple.

The reason they were all purple was because they used a mix of blue and red diodes. which was once believed to be the best combination for growing plants.

The first LED grow lights were made with this combination, many were from china and were absolutely terrible for growing. Thankfully, LED grow lights have improved so much since then, and are now built with mostly white diodes with a mix of red and blues.

Why Are LED Grow Lights Purple?

LED grow lights have many diodes that each emit a single color of light. It is the combination of those colors that creates the light we see. Therefore LED Grow Lights that emit a purple light contain a large amount of red and blue diodes.

Why Do LED Grow Lights Use Mainly Red And Blue Diodes?

Plant Photosynthesis depends upon the absorption of light by photoreceptors and pigments in the leaves of plants. The most well-known of these pigments is chlorophyll-a, but there are many accessory pigments that also contribute to photosynthesis.

The relative light absorption of chlorophyll pigments is one of the reasons why red light has become popular among LED grow lights. Not all PAR light contributes to photosynthesis equally, though we now understand that other wavebands of light such as green, do play an important role in this process.

Colors such as green, could enhance the leaf expansion rate and stem elongation, which in turn results in higher yields.

Since photoreceptors in plants also have their own ranges for light absorption, they co-regulate processes that create plants’ form and structure depending on the spectral mix they receive.

For instance, higher ratios of blue light can induce more robust root growth, more favorable plant biochemistry, and a hardier structure. But these effects may not be as pronounced when more red light is introduced.

The two most important light colors to place in an LED grow light are: red and blue. Therefore many manufacturers purely made LED grow lights with blue and red diodes. Blue diodes for plant growth and red diodes to promote flowering. Which in turn gives LED grow lights that famous purple/pink color.

However, from an economic perspective, red and blue LEDs are the cheapest to produce. And this is why most LED grow light manufacturers go with simple red-blue combinations.

When you combine them in LED grow lights they give your plants the light they need to stimulate those two patterns of growth at the same time, which is mostly what your plants need to grow.

Purple LED grow lights do grow and flower plants well. Due to new research though we are now starting to realize that white diodes with a mix of red and blue is better for plants.

The Benefits Of Purple LED Grow Lights

Now that we know why specific wavelengths of light are used in an LED light, let’s talk about why that purple light is so beneficial to your plants.

HIDs shower plants with every wavelength possible, but purple LED lights isolate the specific blue and red wavelengths of light that benefit your plant. This is great for plants because it provides exactly what the plants need to grow and flower.

The ratio of red to blue diodes in a grow light will also benefit your plants. Whether you have more red than blue or more blue than red, you’ll get a lighter or darker shade of purple. Each shade has its own benefits, so you’ll want to find the right combination for your grow room.

More blue light will grow taller plants, where as more red light will produce more leaves and bigger yields. They also cost less to purchase and run than HID or similar lighting.

The Downside of Purple LED Grow Lights

One of the downside attributes of this combination fixture is on humans. They are no doubt good for plants, but for humans, they can affect you're vision.

The effect of purple light on human eyes confuses you're vision when looking at you're plants. Thus, it will be harder to recognize the plants and their parts. As a result, it will be more difficult to work on them and to see if there are any problems.

The Best LED Grow Light Spectrum for Plant Growth

Full Spectrum LED grow lights for example, are the newest technology designed to replicate the only real full-spectrum light source, the sun.

A full-spectrum lighting system, especially that which contains lights of all wavelengths, like (UV, and IR), are far more effective and practical. UV and IR diodes aid you're plants in the flowering process and can help increase yields. While also improving the smell and taste.

RELATED POST: Top 5 Full Spectrum LED Grow Lights in 2021

Plants only require PAR light for photosynthesis. So, if your grow light is optimized within the PAR spectrum, you’re going to get the most bang for your buck when it comes to minimizing electrical costs while maximizing plant health.

Beyond PAR, it’s important to choose a light spectrum that’s:

  • best for the environment you’re growing in (greenhouse or indoors)

  • tailored to your plant’s growth phase (propagation, vegetative, flowering, or finishing)

  • specific to the cultivar being grown

Although you cannot mimic sunlight, you can still use the LED full spectrum to you're advantage. Luckily, there are many grow lights available with designs intended to do just that. Lets take a look at some of the advantages of full spectrum LED grow lights.

Greater Efficiency The energy saving that growers can expect from using a very efficient LED grow light, instead of an HID grow light, is around 48%. This percentage may drop to as low as 20% with less efficient LED grow lights.

Cooler Temperature LED grow lights produce significantly less heat. This means you won’t spend as much energy on cooling with an air conditioner.

It also makes them better for growing in small spaces. This gives them the ability to be placed closer to plants due to the low heat output, sometimes as close as a few inches!

This is advantageous to growers growing in areas limited by height. This feature also allows growers to place the lights closer to plants to ensure optimal light penetration deep into the canopy.

Longer Lifespan One of the reasons why LED lights are increasing more in popularity is that they have a longer lifespan. A top quality set of LEDs can last as long as 50,000 to 100,000 hours. Which means they require less maintenance. So you won’t have to worry about changing bulbs every year compared to HID Lights.

The Full Spectrum A major advantage of using LED grow lights is the huge spectrum of energy they provide. When you choose LED, you don’t have to worry about switching out lights as your crops mature through their growth cycle. Even better, you can actually install a system that’s tailored specifically to the type of crop you grow.


As you can tell, there are definitely some BIG advantages when choosing a full spectrum LED grow light, but whether they’re the best choice for indoor growing depends on a few things. For a lot of growers, the low temperature, efficiency, lifespan, size and spectrum of LEDs make them ideal for indoor grows, especially if you are growing in a grow tent.

RELATED POST: 8 Grow Tent Essentials You Need To Own

Overall full spectrum LED grow lights are going to be you're best option. Blurple grow lights can and will grow plants, but there are of course better options. Full spectrum LED grow lights contain lights of all wavelengths and will overall produce much healthier and bigger plants. Blurple lights may have been the best in the past, but with the current advances in technology, full spectrum is the way to go.

So, what do you plan on growing? And with what grow light?

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