Updated February 26, 2022 by Mark Marino
Strange as it may seem, not all light is created equal. In fact, not all light is created visible. Most light is invisible to humans, even as another life on Earth is capable of seeing it, or at least benefitting from it. The most obvious and best example of this is the benefits a plant gets from the ultraviolet rays of the sun.
Plants turn sunlight into the energy they need to perform the chemical reactions that water enables. But the part of the light they need is not the visible white/yellow light that we usually see. The question is then: Can plants grow inside a house under a different wavelength? What about the same wavelength made artificially?
The most common expression of this question asks whether or not plants can grow under ordinary incandescent or fluorescent light bulbs. The answer is no; in order for plants to grow, they need certain wavelengths of light at certain intensities that ordinary light bulbs do not provide.
This does not mean that plants cannot be grown indoors with artificial lights, however. It is all a matter of what kind of plants you have, how much you want to grow, and what kind of light you need to get that done.
What Kind Of Light Do Plants Need?
See, light exists on a spectrum. Some light hits your eyes more frequently. This is because it has a shorter “wavelength”, and as a result of this shorter wavelength the light takes on a different color.
Purple and blue light has the shortest wavelength of all visible light. A short-wavelength means the light collides with anything it touches more frequently. This makes purple and blue LED lights a feast for light-starved greenhouses.
A plant feeding off of blue light will get nearly double the nutrition than it would from an orange light of the same intensity. It is a simple matter of the blue light “hitting” the plant at a higher frequency than the orange light. Blue light is recommended over purple light, however.
Even though purple light has an even higher frequency than blue light, it can actually be so high that plants can’t absorb it. There are many kinds of light that are not visible to the human eye for the same reason.
In this case, the human eye can identify a color of the light (purple) that plants have trouble absorbing. You can use lights to supplement your greenhouse even if it gets direct sunlight. This is because the big danger of sunlight is the heat more than the light.
As stated before, there are many types of light that are not visible, and these types of light are what carry heat with them. Gamma rays and infrared light is the light that generates the most heat. Luckily, you will actually have a hard time finding any light fixtures that output this. LED lights will not output it at all.
A blue LED light is not going to output the invisible ultraviolet or gamma rays the sun does. This makes them safe to use to your heart’s content. Just so long as you do not drive up your electrical bill.
What Kind Of Plants Can Be Grown This Way?
The best plants to grow under artificial light are small herbs and weeds, like basil, onion, and oregano. Amusingly, this has less to do with the amount of light they need and more to do with the amount of space they take up. One of the biggest obstacles you will find yourself running into when growing plants indoors is space.
Technically speaking, these LED lights will also allow you to do things like grow strawberries in your closet and tomatoes in your bathtub (if you are so inclined). However, both of those fruits have the drawback of having root systems that frequently outgrow an ordinary plant container, especially normal planting pots.
Many plants can be grown with LED lights, but few can be grown in circumstances where LED lights are necessary. There is a situation where these two do not overlap, however. If you have a basement that has a dirt floor, you can use LED lights to grow out of that dirt without worrying about space.
Do You Need LED Lights, Or Will Any Blue Lights Work?
This is the question that people usually arrive at after they have wrapped their heads around the needs of plants and the possibility of lights. So, since blue light benefits plants because of its frequency, then do that blue light need to be output by an LED light in order to benefit the plant?
Or, returning to the original question, can it be output by a normal lightbulb? Surprisingly, the answer is yes. But only technically. In fact, blue light does not even have to be the native light of the lightbulb. You can wrap a blue fruit roll up around the lightbulb and it will turn the light blue, changing its wavelength.
You will, however, notice some issues, and these issues are why a normal lightbulb will only “technically” work. The first issue you will notice is that no matter how you filter the light, it will be dimmer.
This is because a filter allows only certain light to pass through. Since only a small amount of a normal lightbulb’s light is blue, only a small amount of light is going to pass through the filter. This means that even though the light is hitting the plant quite frequently, there is not much light hitting it.
LED lights are also far, far more energy-efficient than normal lightbulbs. So, even though a normal light bulb can do what an LED light does, an LED light will do its job better and cost less energy.
While a normal lightbulb can help a plant grow, it requires so many extra steps to get to the point where it is effective that by the time you are there you are basically not using a normal light bulb anymore. They simply are not strong enough in the way a plant needs. Use LED lights and your problems will be solved.