Public interest in indoor gardening is blooming, and lighting technology has grown to support it! Starting seeds early, enjoying veggies year round, and protecting delicate leaves from pests are just some of the reasons to bring your garden inside. Your indoor garden will need an indoor sun, which is where LED grow lights enter the picture. This fairly new tech has germinated a lot of questions about UV radiation and safety, so read on to find out what facts about LED grow lights have emerged from the dark.

Do LED grow lights emit UV rays?
Yes, many LED grow lights emit UV rays.
UV rays, also known as ultraviolet radiation and ultraviolet light, are emitted from natural sources, like the sun, and artificial sources, like tanning beds and some kinds of lights. Although overexposure to UV radiation can cause cancer, in small amounts, UV exposure is beneficial for both humans and plants, stimulating vitamin D production in people and robust growth in plants. This is why many LED grow lights have been specially engineered to emit UV (most LED household lights don’t emit any). Other kinds of grow lights, such as HID (high intensity discharge) lights, also emit UV light.

Why do grow lights emit UV light?
UV light helps plants grow.
Although UV radiation can be harmful to both plants and animals in large amounts, within correct ranges, UV light encourages indoor plants to be stronger, brighter, and more resilient.
Plants exposed to UV light were not only more disease resistant, but also made bigger fruit (and more of it).

Do the UV rays from LED grow lights cause cancer?
Not usually, but it is a risk.
The UV from most sources of indoor lighting is not harmful to humans, but the higher intensity of grow lights’ UV radiation is worth being mindful of, particularly for those with a family history of skin cancer. You can moderate your exposure to UV radiation from your LED grow lights by wearing long-sleeved shirts, hats (if the light is installed overhead), choosing grow lamps with lower UV intensities, and only using the lights for the recommended amount of time.

Do LED grow lights damage eyes?
Possibly.
Because LEDs are a fairly new technology, researchers are still studying the long-lasting effects of LED exposure. However, early research tentatively suggests humans limit their exposure to all blue light—(which is the peak spectral output of LEDs)— to avoid skin and eye damage.
Smartphones, laptops, desktop computers, and tablets also emit blue light.
Some studies suggest that just one hour of exposure is enough to generate oxidative stress, encouraging wrinkles and other premature aging!
Try using glasses with amber lenses to protect your eyes from all forms of blue light.

Do LED grow lights contain heavy metals?
Not anymore, but they used to.
In the past, LED lights contained many heavy metals such as lead and mercury. However, technology has changed since then and LED lights no longer contain harmful materials.

Is it safe to leave your LED grow lights on all the time?
Yes, but you probably don’t want to.
LED grow lights are cooler and more efficient to run than other kinds of grow lights, but most plants require a daily period of darkness in order to thrive.
Most plants require 6 hours of darkness to regenerate phytochrome, which is important to regulate seed germination, among other processes. Generally speaking, for bright light plants, you might need to use the light for 8 to 10 hours a day.

Does leaving my grow lights on all the time create better growth?
No—plant growth is decided by quality of light, not quantity of light.
Ordinary fluorescent shop lights will need to run much longer than intense HID lights. A plant cozied right up to a light source will need fewer hours of light than a plant placed several yards away.
DLI (Daily light integral) measures the amount of quality light a plant receives.
Plants’ DLI needs vary based upon species, stage of life, and the season. Tender microgreen sprouts can make do with the natural light of a windowsill, but energy-starved fruiting tomato plants will need a lot of intense light to mimic the power of the summer sun.