Hi all! Sooner or later in your indoor gardening journey you are going to hear all about Grow Lights. And a lot of info about them – in fact you may be up to your eyeballs in information overload. After all there’s the type of energy that powers the lights, then there’s the color of them too, and then the design. If it sounds like a lot to take in, I know where you’re coming from. There’s purple lights and white lights. Which should you choose?
Shopping for light bulbs has been something of a beffudling endeavor since LED replaced “the norm” (not sure what that was….) There were these corkscrew-shaped bulbs that supposedly were “energy saving” and then they got fazed out. I used to see the singular term “watts” on every box and now I see “lumens”. But I digress a little, Let’s begin by looking at the topic of grow lights from the early beginning.
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The Beginning: HID Lights
In the past, grow lights were exclusively HID (High Intensity Discharge” ) and used in commercial growing settings. The bulbs that went into these lights was powered by xenon gas that traveled between 2 electrodes from one end to the other. The light produced was very much reminscent of natural sunlight. These bulbs used to power other mechanisms, too, like car headlights.
Periodically, they had to be changed and required careful handling as fingerprints and natural skin oils could degrade the light quality. There are two main types of HIDs – there’s the HPS – (High Pressure Sodium) which emit light in the reddish/orange spectrum, that supports the fruit-producing plant stage. The other is in the blue spectrum , known as MH (Metal Halide) and used more in the early stages of growth – responsible for producing strong roots and growth of foliage.
HIDs have gradually been fazed out (although there are some people who still use them today) Now they are supplanted by the highly popular LEDs which are universally in most lights today. LED stands for Light Emitting Diode and works very differently from bulbs – diodes are actually chips that arranged on a circuit board Although they have a narrow color range, they emit light from different points, but when arranged together they can appear to be any color. HIDs are different in that the light all comes form one source.
This is what the underside of one of my LED grow lights look like. Notice how the little squares look white and red, but they are purple when switched on!
One reason LED lights are preferred by gardeners over the old-school HIDs is the fact that they are cooler. This is true of LEDs in general, not just grow lights…One thing I love about the newer models of Christmas light strands is that they are cool to the touch. I remember inheriting an old set of my grandmother’s C( holiday lights which get so hot I wasn’t comfortable with the idea of using them. So there’s that – HID lights get fairly hot, so they needed to be elevated above plant rows by at least 18″.
If plants’ foliage gets hot along with cold roots, it could lead to a lot of stressed-out vegetation. Therefore, to this day, HID lights make sense in colder environments only. The second thing is the fact that LED lights are more energy efficient.
Are there other types of light used in gardening nurseries? Yes.There is a third main type of grow light that is popular on the market today, and that’s the CFL (compact fluorescent lighting) Instead of the well-known long tube they are in the bulb shape you may be familiar with for everyday use. Long fluorescent tubes are not only cumbersome to deal with, they are fragile, God help you if one of them shatters.
They emit light that meets the criteria of optimum PAR spectra They have replaced incandescent lights in efficiency and output. You can find them in that “corkscrew” shape I descibed earlier.
Ideally, look for “full spectrum” when it comes to good lights. When I was reading about lighting the terms broad and full spectrum came up a lot, it almost made me think about CBD oil. Lol. “Lumens” is the metric used on LED lights and refers to strength of light visible to the human eye but it doesn’t tell you exactly what is usable by plants, which is where the PAR metric comes in.
How Colors Of Light Affect Plant Growth
On with that, now let’s talk about the different colors on the spectrum and how they are influential in plant growth.
You may or may not be familiar with color spectrums, wavelengths, the color prism, etc…all related to science. If not that’s OK too. We’ll focus on how this science relates to plant life. There is a scale known as the PAR (Photosynthetic Active Radiation) which is a metric of light on the spectrum including wavelengths measured in NM (nanometers.)
The most abundant phase of plant growth is encompassed by the 400-700 NM range. Light wavelengths that fall outside of this spectrum still have value, but figure less prominently. Red is on the highest end (the 700) and the color that produces the most fruit producing. Blue on the 400 range end is the growth color.
Green factors in the least after all chlorophyll is the green pigment that plants have in abundance so all it does is reflect it back.
White, on average, is good….I have 2 white LED bulbs with the standard socket in my grow room and 2 more in the living room for my houseplants to supplement them through the wintertime. The latter, of course, being decorative, I do not have any other goals for them other than to stay healthy.
But for immature seedlings, I’d say blue is the best choice, at least initially. Of course, the lights I use for them are purple, combining both the red/blue spectra.
Grow Lights also come in different styles: Bulbs , Ballasts, and strip lights.
I like the strip lights as you can affix them with double sided tape, use hardware or zip ties -which is what I did since the only way to do so with the shelving I have was through one of the open spaces.Ballast lights are bulky and to be mounted overhead.