Understanding LED Grow Lights
There are a number of reasons why LEDs are proving popular as grow lights, but to properly understand these it’s helpful to first recap the qualities that are most desirable in a grow light, and also to examine the characteristics intrinsic to LEDs.
It’s also worth understanding why there has been more heat than light generated around this subject, with some folk adamantly claiming that LED grow lights don’t really work and others insisting instead that they do in fact work very well. Both sides are right; they’re just comparing apples with oranges, in other words not talking about the same products, as will become apparent.
Understandably, many folk are seduced by the idea of a “bargain” but the fact is that those who pick up a cheap LED grow panel on eBay (typically incorporating 225 lamps and using “only” 14 watts or so) are set for a bad experience (and then likely blame the technology). Quality LED grow lights are realistically priced, save a fortune in running costs and pretty much live up to their performance claims.
But back to the introduction… the purpose of a grow light is evident in the name itself – to help plants grow. Usually the intention is to be able to grow plants indoors (i.e. in the absence of sunlight) and/or to also better control the rate of growth, size and other characteristics.
The advantage of an indoor growing environment is that you can very precisely control the factors crucial to plant growth and tailor them for specific types of plant. All plants require warmth, water and nutrients (absorbed from the soil or using a hydroponic system where the plant sits in nutrient rich water). But most crucially, they need light and, as we shall see, not just any old light either.
How Plants Use Light To Grow
The way that all plants grow is by photosynthesis, the process whereby carbon dioxide (CO2) is converted into the organic material that makes up the plant (carbon, proteins, sugars and so on) using energy derived from sunlight. This energy is absorbed through special proteins containing chlorophyll molecules that reside in photosynthetic cell membranes called chloroplasts.
Now the point about chlorophyll is that it only absorbs light from particular parts of the spectrum, mostly the blue and red parts. It is especially poor at absorbing light from the green part of the spectrum which is why chlorophyll itself and anything containing it (such as plant leaves, grass and so on) appears green, since that area of sunlight is reflected rather than absorbed.
In fact, chlorophyll is so effective at absorbing light outside the green part of the spectrum that these colors are only revealed when the chlorophyll decays – hence the reason we have to wait till Autumn to see the reds, browns and yellows that are present in leaves but masked by the chlorophylls (yes, plural)…