One of the most commonly used terms when referring to the power of a given grow light is the word lumens. For years, it has been the standard measurement of the growing capability of metal halide and high pressure sodium grow lights. The problem is that this term has been used incorrectly for over 30 years. In this article, we will explore the real meaning and correct use of lumens and further describe what you should be looking for when it comes to choosing LED grow lights that pack the most growing-power for your dollar.
What are Lumens and Lux
Lumens and lux are both measurements popular with grow light manufacturers - both HID and LED - to give potential customer a reference point for the relative brightness of various lights. In some jurisdictions, a lamp's lumen output rating must be on the label as required by law. What we are told (and have been for years) is that the higher the lumen rating of a given light, the better, faster, bigger, etc. your plants will grow.
But there is one MAJOR problem with using Lumens as a reference point for growing plants.
By definition, a lumen is a measurement of how bright (the power) a light is perceived by the human eye. The term lux is very similar to lumen in that it measures the intensity of light, however, it also takes into account the total area covered by a given number of lumens. For now, don't get bogged down by the technical side, just know that lux and lumen both measure the intensity of light to the human eye.
So what's the big deal? A bright light is good, right? The sun does a pretty good job at growing things and it's really bright. Don't we want to mimic the sun?
Well, yes and no . . .
Lumen & Lux Are Irrelevant To Plant Growth
Unless the plants under your grow lights have eyes, lumens & lux make zero difference in how well your plants grow. Plants respond most efficiently to light that is beyond what humans can perceive so it does not necessarily matter how bright your light is. As a matter of fact, 80% or more of the light emitted by either the sun or from HID lights, goes unused by plants for photosynthesis. It is that portion of light that we humans see with our eyes and can register as being bright.
What matters most are the wavelengths of light that your grow light emits. When an LED grow light manufacturer rates their lights based on lumens, it is flat out misleading and irrelevant. Some manufacturers realize that people are starting to learn about this and are now skipping the word "lumen" and just showing pictures of how bright their light is. The result is the same - a bright light does not guarantee big yields.
Choosing An LED Grow Light For The Right Reasons
Making an investment in LED grow lights is nothing to take lightly. There are many factors that, if considered carefully, can almost ensure big yields. But you must take the time to educate yourself and explore the manufacturers claims. You best bet is to be sure the lights you buy come from a manufacturer that offers not only a warranty against defects but a guarantee that, if you don't like the results, you can return the lights for a refund.
Be sure the light you choose covers the correct spectra and offers an appropriate amount of power for your specific grow operation. This article is only part of a multi-part series about growing cannabis with LED grow lights. Come back often for updates and don't hesitate to contact us for help if you need it.