Grow lights try to replicate the spectrum of light that plants receive from the sun.
You can find grow lights at your local hardware store or online, but the choices can feel a bit overwhelming. By learning a little but about what’s available, you can choose the grow lights that are best for your plants.
Now, everyone knows that most plants need light to grow. What you may not know is that plants need very specific types of light to perform photosynthesis. Grow lights can provide the right light for your indoor plants and windowsill gardens. Grow lights can also used to get a head start on the spring growing season, by planting seeds earlier than they could be started outdoors.
This is not going to be an in-depth scientific post about grow lights. The topic is too complex and new research is emerging that can alter the usefulness of old information. That being said, there are some facts about plants and light that can help you make the best choice when considering grow lights.
Many popular houseplants are shade-loving tropicals that evolved under the jungle canopy, where only filtered light was available. Peace lilies, African violets, and coleus can thrive without added light, but it’s not enough for many herbs and other edible plants. Even sunny windows that provide enough sunlight in summer, may need supplemental help come winter’s shorter days and weaker light.
What is the right light?
Picture a rainbow. That arc of color is the range of visible light, organized by wave length. Plants need the full spectrum of color to grow and thrive. Plants that don’t get enough of the right sort of light tend to grow long and spindly. Plants use very specific ranges of light waves for photosynthesis and different stages of development. It should come as no surprise that light quality changes throughout the year. Spring time sunlight is more in the blue and violet range, which encourages vegetative growth of roots, stems, and leaves, and promotes disease resistance. As the Earth’s tilt and rotation bring us through summer and closer to autumn, the light quality changes to the more red end of the spectrum, encouraging flowering and other reproductive growth. The light used by plants is measured using an index called the PAR value. PAR stands for Photosynthetically Active Radiation.
Standard household light bulbs emit light most heavily in the orange and red end of the spectrum, leaving plants without the wavelengths they need to properly perform photosynthesis. According to NASA, the range of light used to grow plants can actually alter their nutritional value and antioxidant content. “How they are grown and then consumed in space could have a positive impact on people’s moods and could protect against radiation in closed environments.” (Dr. Ray Wheeler) Hey, in my humble opinion, Earth is a closed environment, so we could all benefit from making sure that the food we eat is grown in ways that promote good health and positive moods!
Types of grow lights
There are three basic types of grow lights: high-intensity discharge lights, light emitting diodes, and fluorescent lights. Within those three categories, there are several options. This [modified] list from Wikipedia makes it a little easier to understand:
High-intensity discharge (HID) lights - currently the most popular, but they require some heavy duty electrical connections and each bulb type must have a specific ballast. (Just because a bulb screws into a socket does not mean you are using the correct combination.)
Light-emitting diodes (LEDs) - efficient and economical; used by NASA; can be plugged directly into a household electrical outlet; this bulbs do not get hot, unlike many others; while more expensive than most, LEDs last profoundly longer (11 years)
Fluorescent lights - efficient and economical; some people get migraines or have seizures because of fluorescent lights
Many of these bulbs are available at a variety of intensities, the same way as regular light bulbs. To pick the right combination of intensity and color spectrum, you will need to learn about the sunlight requirements of your indoor plants. There are grow light bulbs that screw into traditional lamps, stand-alone planters with their own grow lightrs, and you can build your own seed starter set-up with inexpensive shop light hoods installed with fluorescent grow lights.
How do you use grow lights?
I hope this information inspires you to grow more of your own food. You can ask your garden questions on my Home page.