Many LED lighting suppliers will say that full-spectrum LED grow lights are the best option for growing plants because they mimic the natural light from the sun. The argument goes:
“Plants have grown under sunlight for millions of years. Why would we want to change what mother nature knows is best?”
Well, we want to let you know that there is no such thing as a full-spectrum LED grow light.
There, we said it.
But before we get a flood of messages from concerned growers wondering what all the confusion is about, let’s first uncover what full spectrum means. Then we’ll let you in on the truth about full-spectrum LED grow lights so you can make the best grow light choice for your facility.
What is a Full-Spectrum LED Grow Light?
A full-spectrum LED grow light is simply a marketing term that implies that your grow light closely resembles light from the sun. This marketing term comes from the concept of “full-spectrum light,” which in recent years has been used to refer to electromagnetic radiation from the UV to infrared wavebands.
The History of the Full-Spectrum LED Grow Light
The full-spectrum LED grow light is the newest evolution of an already confusing term. Originally, full-spectrum light described the only real full-spectrum light source, the sun.
Over time, the term began to take on other characteristics of sunlight. The commercial lighting industry began using the name “full-spectrum” to sell lights that produced a Color Rendering Index (CRI) over 90. Humans perceive colors more accurately under light sources with a CRI over 90, much like how we see colors in our natural world under daylight. This was a beneficial feature for human environments such as offices, outdoor spaces, and others.
With the advent of horticultural lighting, companies once again began to borrow the term. Only this time, they claimed that full-spectrum LEDs could reproduce the effects of sunlight for plants.
Thus, the full-spectrum LED grow light was born. Unfortunately, lighting for plants is not quite that simple.
Problems with Full-Spectrum LED Grow Lights
There are many issues with the concept of full-spectrum LED grow lights. For starters, just because you name something, doesn’t make it true. This rhetoric may have made sense for lighting designers interested in selling lights so humans could see, but plants require light to feed, grow, and live.
There are three major problems when talking about full-spectrum grow lights:
- Full-Spectrum Grow Lights Aren’t Optimized for Plants
- Full-Spectrum Grow Lights Don’t Include the Full Solar Spectrum
- Full-Spectrum Grow Lights Are Not Dynamic Like the Sun
We’ll briefly look at these problems with full-spectrum grow lights one-by-one, so you can understand how deep the roots of this problem run:
1. Full-Spectrum Grow Lights Aren’t Optimized for Plants
A major problem with many full spectrum LED grow lights is that they are designed to give the appearance of daylight without being custom-tailored for rigorous plant growth.
It’s the reason why we at LumiGrow coined the phrase, “PAR is for plants and Lumens are for humans.” Not all wavelengths of light are optimal for photosynthesis. Plants photosynthesize electromagnetic radiation in the 400 to 700 nanometer range, known as Photosynthetically Active Radiation or PAR. So, plants don’t care how bright your light fixture appears to you.
Still, most full-spectrum lighting companies build fixtures with this visual appeal in mind.
When you hear that the diodes in your full spectrum grow light are 3,000k to 4,500k, or 5,000k+, this degree of Kelvin (K) refers to how “cool” or “warm” your light is in appearance.
Our understanding of plant photobiology has come a long way. We understand much more about plants than to be using human lighting metrics to design our grow lights.
Our goal as growers is to improve the lighting characteristics most important for plant growth. This means not only getting enough PAR light, but also the right mix of light spectra, which brings us to problem #2.