What distance should LED grow lights be from plants?
Written by
Kiana Okafor
Reviewed by
Prof. Charles Hartman, Ph.D.The ideal distance for the light can either make or break your indoor garden. If the LED grow lights are placed too close to the plants, you risk burning the plants. If they are too far away, the plants will grow slowly and not thrive. I learned this the hard way after growing out some seedlings. You want to have specific distances, based on the plant stages, to achieve your best results.
Seedling Protection
- Use dimmers at 40-50% power initially
- Check for leaf curling daily
- Raise lights immediately if bleaching occurs
Vegetative Optimization
- Lower lights 2 inches weekly
- Watch for compact internodal spacing
- Maintain 75-85°F canopy temperatures
Flowering Precision
- Measure bud development weekly
- Lower lights 1 inch per bud stage
- Rotate plants for even exposure
Seedlings require soft light. To begin, hang the light at thirty-six inches above the seedlings. I burned delicate seedlings at twenty inches. You only prevent this drying effect by hanging the light up higher in the room. You can also use a dimmer at 50% power and gradually increase it over time. Increase the intensity over two weeks, slowly increasing the power.
Vegetative plants flourish when they are closer to the lights. For this type of plant, I would recommend lowering the lighting to a distance of twenty-four inches. My basil grew more bushy like this. You are promoting compact growth instead of stretching. Be sure to check for light stress daily. If you notice the leaves starting to curl up, raise the lights immediately.
Flowering is about gaining some allowances. Start at eighteen inches while transitioning into a flower. Drop to twelve inches when buds are forming. I am likely adjusting every week during this stage. You are avoiding light burn while accommodating maximum yield. Observe bud development closely.
There are differences between models in terms of the light intensity they provide; therefore, we suggest reviewing your manufacturer's PAR maps to determine the optimal model for your needs. For example, my Samsung LEDs request a different lighting height than my cheaper brand LEDs. You would measure this with a PAR meter. Survey and scan the canopy at multiple points. Make adjustments from there based on your stage requirements.
Temperature guides your distance decisions. It is best to keep the leaf surface temperatures below eighty-five degrees Fahrenheit. I use infrared thermometers daily to ensure we maintain ideal growing conditions. If you see yellow leaf edges forming, that demonstrates heat stress. Increase your distance immediately when you see that effect.
Read the full article: Ultimate Guide to LED Grow Lights for Plants
