The hand-shadow light test

The short answer: Hold your hand 12 inches above a sheet of white paper at midday. A sharp shadow means bright light, a soft shadow means medium light, a faint blur means low light, and no shadow means the spot is too dark for any plant.

Plant labels love to say “bright, indirect light.” But what does that look like in your living room? Our eyes adjust so well that a room can look bright to us while giving a plant only a fraction of the light it needs.

There’s a free, 30-second way to find out — and all you need is your hand.

Try it now: our interactive hand-shadow light test walks you through it and tells you which plants will thrive in that exact spot.

How to do the hand shadow test

1. Pick the time: around midday, on a clear, sunny day. Turn off lamps.
2. Put a sheet of white paper exactly where the plant will sit (on the shelf, floor or table).
3. Hold your hand about 12 inches (30 cm) above the paper, between the paper and the window.
4. Look at the shadow and compare it to the guide below.

That’s it. Repeat it in every spot you’re considering — you’ll be surprised how much light changes in just a few feet.

What your shadow means

Shadow	Light level	What grows there
Sharp and dark, clear finger outlines	Bright / some direct sun	Succulents, cacti, aloe, jade, ponytail palm
Soft but clearly visible, fuzzy edges	Medium (bright indirect)	Most houseplants: pothos, monstera, spider plant, peperomia
Faint blur, you can barely see it	Low light	ZZ plant, snake plant, cast iron plant, parlor palm
No shadow at all	Too dark	Nothing long-term — add a grow light

Why light matters more than anything else

Light is a plant’s food. Water and fertilizer are just ingredients; without enough light, a plant can’t use them. That’s why so many plant problems — yellow leaves, leggy stems, no new growth, soil that never dries — actually start with a spot that’s too dark.

It also changes how you water. A plant in low light drinks slowly, so the soil stays wet longer. If you water it like a plant in a sunny window, the roots rot. How often to water, by light level →

Things that change your result

• Distance from the window. Light fades fast. A plant 6 feet (2 m) away from a window can get a tenth of the light on the windowsill.
• Window direction. In the US, south- and west-facing windows get the most sun and north-facing ones the least. In Australia it’s flipped: north-facing windows are the sunny ones and south-facing windows are dim.
• Season. The sun is lower in winter. A medium spot in July can become low light in December in the US (and in June in Australia). Repeat the test when the seasons change.
• Obstacles. Trees, balconies, buildings next door, sheer curtains and dirty glass all cut light.

Signs your plant disagrees with the test

Plants are the final judges. Move a plant closer to the light if you see:

• Long, stretched stems with big gaps between leaves
• New leaves smaller than old ones
• Variegated leaves turning plain green
• The whole plant leaning toward the window

And move it back a little if you see bleached, pale or crispy brown patches on the side facing the window — that’s sunburn.

The shadow test in numbers

If you’d like to compare your result with a light meter app or a plant label, these are the ranges commonly used for houseplants. Phone apps vary a lot, so treat them as ballpark figures:

Shadow	Light level	Foot-candles	Lux
Sharp and dark	Bright / some direct sun	1,000+	10,000+
Soft but clear	Medium (bright indirect)	250–1,000	2,500–10,000
Faint blur	Low	50–250	500–2,500
No shadow	Too dark	Under 50	Under 500

For comparison, a typical office under ceiling lights is only around 30–50 foot-candles — which is why so many desk plants slowly fade.

Window by window (US homes)

Window faces	Sun it gets	Right at the window	3–6 feet back
South	Most hours of sun, strongest in winter	Bright — succulents, cacti, jade	Medium — most houseplants
West	Hot afternoon sun	Bright — can scorch leafy plants in summer	Medium
East	Gentle morning sun	Medium-bright — ideal for most houseplants	Medium to low
North	No direct sun	Medium to low	Low

In Australia, swap north and south: a north-facing window is the sunny one.

How the seasons change your result

• Winter: days are shorter and the sun is weaker, so a spot that was medium in July can test low in December. But the low winter sun also reaches deeper into south-facing rooms — a plant 6 feet back may suddenly get direct rays for an hour.
• Summer: a west window that was fine in spring can scorch leaves pressed against hot glass. Move sensitive plants back a foot or two.
• Trees and neighbors: a leafy tree outside can turn a bright window into a medium one from May to October, then bright again when the leaves fall.

Test each spot twice a year: once in summer and once in winter.

Common mistakes with the test

1. Testing in the morning or late afternoon. The sun is low and the shadow looks longer and softer. Midday gives a fair reading.
2. Testing on a cloudy day. Everything reads a level darker.
3. Holding your hand too close to the paper. Even weak light makes a sharp shadow from an inch away. Keep it about 12 inches up.
4. Lamps on. Room lighting adds a second, confusing shadow.
5. Testing the windowsill when the plant will live on the coffee table. Test the exact spot.

Grow lights: the numbers that matter

If the spot failed the test, a grow light fixes it. What makes the difference:

Setting	Starting point
Bulb type	Full-spectrum LED (white light is fine; purple isn’t necessary)
Distance from leaves	12–24 inches for a bulb in a lamp; follow the maker’s guidance for panels
Hours per day	10–12, on an outlet timer
Signs it’s too strong or close	Bleached or crispy spots on the top leaves
Signs it’s too weak or far	Stretching toward the light, small new leaves

Plants also need darkness. Don’t leave grow lights on 24 hours a day.

Tricky spots

• Skylights: light comes from above, so hold your hand between the skylight and the paper. Skylit rooms often test medium to bright even far from the walls.
• Frosted or textured glass: it spreads light out, so shadows look softer than the light really is. If the shadow is soft but the room feels very bright, read it as medium-bright.
• Covered balconies and porches: the roof blocks overhead sun. Test where the pot will sit, not at the railing.
• Sheer curtains: they cut harsh sun but keep plenty of light. A south window behind a sheer is a great medium spot for monstera and pothos.
• Glass doors and big windows: a floor-to-ceiling window lights the floor far deeper into the room than a small window at counter height. Test at plant height.
• Rooms painted dark: dark walls absorb light; the same window gives less usable light than in a white room.

What if my spot is too dark?

You have two good options:

1. Choose a tough low-light plant and accept slow growth. Here are the 10 best plants for dark apartments.
2. Add a grow light. A full-spectrum LED bulb in a regular lamp, on a timer for 10–12 hours a day, turns a dark corner into a perfectly good plant spot.

Ready to test your own space? Open the interactive hand-shadow light test — it takes 30 seconds and recommends plants for your result. Then use the watering calculator to set a routine that matches your light.