You don’t need an app, a meter, or anything at all to get a fast read on a spot’s light. You need your hand and a sunny-ish day. The shadow a spot casts tells you almost everything about whether a plant can live there — and it’s the honest fallback for when your phone’s in the other room.
How to do it
Around midday on a reasonably clear day, hold your hand (or a sheet of paper) a foot or so above the exact spot — the sill, the shelf, the corner — and look at the shadow it throws.
- Sharp, dark, crisp-edged shadow → direct sun. Full-sun territory — great for sun-lovers, a scorch risk for shade plants.
- Soft-edged but clearly visible shadow → bright indirect light. The sweet spot most houseplants want.
- Faint, fuzzy, barely-there shadow → low light. Tolerators only, and they’ll grow slowly.
- No shadow at all → too dark for most plants. Think grow light, rotation, or a different spot.
Why it works
Shadow sharpness tracks how directional and how strong the light is — exactly the thing your adapted eyes can’t judge from brightness alone. It won’t give you a number, but it reliably sorts a spot into the tier that decides what can live there. That’s the decision that matters.
When you want more than a tier
Measure, don’t guess.The shadow test is the quick, no-tool version. When you want to compare two spots precisely, or track how a spot changes with the seasons, set your phone down and measure. GrowSpot turns that reading into a light tier and scores the spot for the specific plant — the shadow test with the guesswork removed.
