Can LED grow lights damage plants?
Written by
Kiana Okafor
Reviewed by
Prof. Charles Hartman, Ph.D.If not used properly, LED grow lights can potentially harm your plants. If set up incorrectly, you will notice visible signs of damage within a few days. I ended up burning some of my tomato seedlings after using the lights too close. To put it another way, you should understand these risks to protect your specific garden. Preventative action begins at the setup.
Intensity Management
- Use PAR meter to verify stage-appropriate PPFD
- Seedlings: 100-300 μmol/m²/s
- Flowering: 600-900 μmol/m²/s max
Spectrum Safeguards
- Vegetative: 30% blue, 20% red, 50% white
- Flowering: 20% blue, 40% red, 40% white
- Avoid 100% purple spectrums
Environmental Controls
- Maintain 75-85°F canopy temperatures
- Use IR thermometer for leaf checks
- Install oscillating fans for air movement
Light burn is identifiable as leaves having a bleached appearance. It occurs when the light intensity exceeds the plant's tolerance. My basil developed white patches at an irradiance of 800 PPFD. This can be prevented by hanging lights high enough. Seedlings should be at least twenty-four inches apart.
Photobleaching permanently destroys chlorophyll. The affected areas of a plant lose their green color. I saved my peppers by halving their intensity. You can catch early signs of photobleaching by inspecting them at least once a day. Curled leaf edges are an indication that something is wrong.
Improper spectrums lead to abnormal plant growth. Excessive blue inhibits flowering plants, while too much red weakens stems. For example, when my tomatoes were in unbalanced light, they grew sideways. You rely on the manufacturer's spectrum recommendations; full-spectrum white will prevent most issues related to deficiency or excess of specific colors.
Recovery begins instantly after you see damage manifesting. Increase the distance right away by six inches. Decrease intensity by thirty percent for three days. My plants recovered within two weeks. Rapid action avoids permanent loss.
Prevention is always better than a cure. PAR levels need to be measured at the height of the canopy. I often run new lights at fifty percent power initially. You then gradually increase the power level over the next seven days. This allows your plants to acclimate without causing them stress.
Read the full article: Ultimate Guide to LED Grow Lights for Plants
