How close should grow lights be to plants?
Written by
Olivia Mitchell
Reviewed by
Prof. Samuel Fitzgerald, Ph.D.The proper distance from your grow light ensures both that you do not have leaf burn, and you are getting the most from photosynthesis. For seedlings, keeping plants in proximity to your grow light,approximately four to six inches, ensures your plants have strong roots. Foliage plants like a Monstera should be farther away (12 - 24 inches). Highlight herbs should be 6-12 inches away for their optimal potential. Always determine the distance based on your plants' light needs.
Seedling Stage
- Position lights 4-6 inches (10-15 cm) above soil
- Prevents leggy growth while encouraging root development
- Maintain 100-300 μmol/m²/s PPFD intensity
- Use adjustable hanging systems for gradual elevation
Vegetative Growth
- Keep lights 12-18 inches (30-45 cm) above canopy
- Allows light penetration to lower leaves
- Maintain 300-600 μmol/m²/s for foliage plants
- Rotate plants weekly for even exposure
Accurately measure light intensity with PPFD meters. Place the sensor at the canopy level for reliable readings. Use adjustment in fixture height if measurements exceed plant tolerance ranges. For LED panels, start with the manufacturer's recommendations and then fine-tune as needed. Observe the plant's response daily for 2 weeks after the changes.
Be aware of the visual cues for distance adjustments: Brown tips on the leaves indicate the lights are too close, and stems that are stretching toward the lights indicate excessive distance. To ensure equal light distribution, remember to rotate the plants 90° each week. When you add reflective surfaces, such as Mylar panels, raise your lights 2-3" to prevent hot spots.
Unique situations deserve unique attention. For multi-tiered operations, maintain a 12-18 inch distance between shelves. For tent systems, keep lights 18-30 inches from walls to avoid heat buildup. For flowering plants, you can gradually decrease the distance as the bloom progresses. Your plants will thank you by growing like there is no tomorrow.
Read the full article: Indoor Plant Lighting Essentials Explained
