How Far Should Grow Lights Be from Seedlings?
Most seedlings need grow lights 2–4 inches above the top leaves. Too far causes leggy growth. Too close causes leaf burn.
Distance by Light Type
| Light Type | Distance from Leaves |
|---|---|
| LED shop light (20W) | 2-4 inches |
| LED panel (45W) | 6-12 inches |
| T5 fluorescent (24W) | 4-6 inches |
| Full-spectrum LED (100W+) | 12-24 inches |
Distance by Stage
| Stage | Distance |
|---|---|
| Just sprouted | 2 inches |
| 2-3 sets of leaves | 3-4 inches |
| Transplant-ready | 4-6 inches |
How to Adjust
- Plants leggy? Lower the light.
- Leaves yellowing or browning at edges? Raise the light.
- Leaves pale? Lower the light.
- Leaves crisp? Raise the light.
The Hand Test
Hold your hand at leaf level under the light.
- Warm after 30 seconds → too close
- Comfortable → just right
- Cool → might be too far
Common Questions
Can grow lights burn seedlings? Yes, if too close. Leaves bleach and crisp.
How often do I adjust the light? Weekly, as plants grow.
Do different plants need different distances? Yes. Tomatoes tolerate more; lettuce prefers less.
Can I leave the light on 24 hours? No. Plants need 6-8 hours of darkness.
Should I turn the light off at night? Yes. Use a timer. 14-16 hours on.
What if my plants still stretch? The light may be too weak. Add another or lower it.