Brighter light is not always better for gardening

Today, in early 2013, if you've searched the INTERNET for information on lighting for indoor gardens, you have no doubt read the opinions of a lot of people. While much of what you read may be true, there are a lot of preconceptions that are quite simply dead wrong.

These incorrect presumptions about how light and plants interact continue to prevail simply because at first glance it makes sense, and more and more people share their "knowledge". Such is the case with the myth that a brighter light is always better for growing plants. To set the record straight, higher wattage bulbs DOES NOT ensure bigger plants, and here is why.

We typically measure brightness in "lumens", and one lumen is about as bright as a candle flame. This is an indicator of how much white light is produced, and it is in fact a useful number when determining the lighting needs of humans, but often people forget that white light is actually a combination of all the colors of the rainbow.

The human eye makes use of the wavelengths between 350 and 900 nanometers (nm), commonly called the "full visible spectrum". By comparison, plants have evolved using only about half of the visible spectrum, in 2 sections. The blue region of the spectrum around 400 - 520 nm, and the red region, 610 - 720 nm.

In addition to length of day/night periods, plants detect the amount of red or blue in the light they receive to help them determine what season it is. In fact natural sunlight has slightly more blue in it during the spring and decreases as fall approaches. Plants naturally assume they should be growing when the light is blue dominant, and flowering when it is red dominant.

In the case of actually growing plants indoors, while High Pressure Sodium (HPS), Metal Halide (MH) and florescent lighting will almost always be much brighter to the human eye, much of the lights output is wasted, converting electricity to visible light that is outside the red and blue ranges your plants can actually use.

To further confuse home gardeners, many lighting manufacturers and retailers compare various lighting solutions by calculating the watts consumed divided by the output measured in lumens. This is fine way to measure light efficiency for humans, but is quite misleading when to comes to gardening.

Because the light generated by LED grow lights contains only portions of the light spectrum plants actually use they typically create purple light that to the human eye appears dimmer when compared to the same wattage using full white LEDs. This is the time to not believe your eyes. Brighter is not always better.

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