Breaking Down LEDs: Blurple

Blurple: A serious problem with many LED grow lights is their “blurple” color. Blurple is a loosely coined industry term to describe the purple-ish light emitted by lights with only blue and red LEDs. While blurple LEDs and their short wavelengths of light are favorable during a plants flowering and vegetative stage, there are several overseen problems when it comes to blurple.

First, these lights can seriously reduce visual acuity while working under them. Our eyes are focused more on green/yellow, the center of the visible spectrum, which is the opposite of blurple. Even small exposures to blurple light will cause havoc to your eyes when returning to normal light. This problem is so pronounced that manufacturers are producing protective eyeglasses that make it easier to work under blurple LED grow lights. If you have never had the fun of working under blurple you’re not missing out on much. Even with corrective glasses you just feel a bit sick to your stomach. The effect is so pronounced it can even mess with your vision in a greenhouse during the day. While red LEDs are effective, they are not the best solution for all around use for you and your plants.

The second problem with blurple is that it hides many gardening problems because they can’t be seen easily. Common problems such as pests and molds can go completely unnoticed. Plant nutritional deficiencies, which could easily be corrected and save the garden, will hide since the plants look purple or even black under blurple lighting. This leads to a lot of ineffective grows and problems that get out of control when they could've been caught sooner.

There is a serious health issue with blurple grow lights that is not being discussed nearly enough – blurple is really, really bad for the human eye. Our eyes use red, green, and blue cones to perceive colors with a maximum daytime sensitivity at 555nm (green). When there is no green in what we are seeing, our eyes attempt to adjust up to a point of nearly full dilation. Unfortunately, this allows full blue light exposure to the retina a.k.a. blue light toxicity. Constant exposure to blue light can cause retinal damage over time and cause vision problems in the long run.

According to a study at the University of Toledo, when retinol (a molecule within our eyes that allows people to see) is exposed to blue light it kills photoreceptor cells within the eye. It’s a very serious condition because these cells cannot be regenerated.

It’s a mystery why OSHA (or the equivalent in your country) has not shut down the use of blurple LED grow lights in commercial grow facilities. How do you feel when you walk into a grow facility utilizing blurple lighting? Can you tell the difference?