How Far Should a Grow Light Be From Houseplants? Using the SANSI 36W as an Example
Quick answer: There is no universal grow-light distance. For the SANSI BR30 36W, the manufacturer publishes about 265.58 μmol/m²/s PPFD at 1 foot, which makes 12 inches a useful reference point for setup—not a guaranteed ideal distance for every species.
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Why distance changes intensity so much
As you move a bulb farther from the plant, the light spreads over a larger area and intensity at the leaf surface drops. Reflectors and lenses change the exact pattern.
Start with the plant, not the ruler
Low-light-tolerant foliage plants may need less intensity than sun-loving succulents. A plant acclimated to a dark corner should also be introduced to strong artificial light gradually.
A practical starting method
- Start around 12–18 inches for many foliage plants.
- Run a consistent daily schedule.
- Watch new growth for two to three weeks.
- Move closer if growth remains stretched and the plant shows no stress.
- Move farther away if exposed leaves bleach or crisp.
Duration matters too
Light intensity and hours per day work together. A weaker light used longer is not always equivalent to a stronger light used shorter, but both influence total daily light exposure.
FAQ
Should leaves feel hot under a grow light?
No. If leaves are heating noticeably, increase distance and improve airflow.
Is PPFD better than lumens for plants?
PPFD is more directly relevant because it describes photosynthetically active photons reaching an area.