Last updated on October 23rd, 2023 at 08:58 pm
Plants also like LED lights – but quite differently than you do. What we humans consider to be pleasant light does not give the botany in the room any bright joy. They need special light wavelengths for their growth, which warm or cool white household LED lamps cannot provide adequately.
Color temperature, color fidelity and sufficient luminous flux (brightness) are very important for domestic LED lighting. Perhaps you have already found the right lamps for your home, dug deep into your pockets and are now happy about the reduced power consumption in return.
However, this joy is clouded if you notice during the winter that your houseplants look more and more puny. In my case, this could be due to the fact that where others have a green thumb.
With you, of course, it’s different: you know how to care for and nurture. So if the flora is still suffering, there must be other causes. One possibility: your new lighting technology is not ideal; yucca & co. can’t do much with the yellow and green tones mainly emitted by “white” LED lamps. While conventional incandescent lamps still provide a few noteworthy red and orange components in their color spectrum, the most that LEDs can do for plants is a little blue – most likely with cool-white and daylight-similar types.
Especially two colors in demand
For photosynthesis and for the growth of leaves and flowers, indoor botany mainly needs these two colors (marked as dots on the right in the wavelength spectrum of visible light): red (wavelength approx. 660 nanometers) and blue (approx. 450 nm) – preferably in a ratio of 8:1 to 3:1; depending on the plant species and growth phase. A little additional orange can also not hurt in special cases, but usually does not have to be.
A purple/purple light composed in this way would, of course, be completely absurd as the sole living room lighting. However, there is nothing to say against treating your green-leaved roommates to something like this as an additional light source. Frequently, the question is then asked, “Yes, is that also available with energy-saving LED technology?” There is: As “retrofit” lamps for existing sockets, as “panels” for do-it-yourself installation in aluminum reflectors, for example, and as complete luminaires that you only have to hang up and connect.
Forget the household lighting criteria
When selecting these LED plant lights, you can pretty much forget everything that is important with “normal” lighting: color temperature and color rendering index play no role here, and lumen luminous flux values only a secondary one. Instead, it’s about the right wavelengths (already mentioned above) and the actual amount of photons usable for chlorophyll production that reaches the plant.
You do not have to pay much attention to the lumen data, because this value refers exclusively to the brightness perception of the human eye. Since the green/yellow range around 550 nm, which is not needed by plants, appears brightest to our receptors and the wavelengths preferred by green stuff are perceived as relatively dark, even highly efficient LED plant lights achieve only about half the “lumen per watt” values of “normal” LED lamps; i.e. rather 30 to 40 instead of 60 to 80.
What’s more, when it comes to plants, it’s often a case of “chunking instead of chipping”: even for a small cultivation area of half a square meter, constructions with a power consumption of around 50 watts may be necessary. Even complete LED plant luminaires with over 600 watts, wavelength switching and full five-digit lumen values are not uncommon in professional use. For smaller (not “smokable”) houseplants in private households without special growing conditions, much weaker LED lamps will of course do.
Compared with the high-pressure sodium vapor lamps used up to now, this gives you a saving of around 40 to 60 percent. Compared to other types of lamps, it is up to 80%, because all of these convert a much larger part of the energy into heat and their light wavelengths cannot be “composed” so precisely for the needs of the plants. With LED lights, you simply mix the single-diode chips of each wavelength in the required ratio – for example, 32 red and four blue.
High savings potential with long lighting times
The absolute savings in kilowatt hours and euros when switching to LED plant lighting can actually be significantly greater than for other home lighting, depending on the extent of the home botany: plant lights are usually in operation for longer and have a higher power consumption on average, so they use more electricity overall.
In addition, colored LEDs are guaranteed to last up to 50,000 hours, or even 100,000 hours in the professional sector. In uninterrupted operation, that would be just under six years – more than twice the average life of my poor little houseplants.