Succulent light checker

Nobody can tell you how many hours of sun your windowsill gets without standing in your room — and a lux number would be a made-up one. What can be judged is the spot: which way the window faces, how far back the plant sits, and what's between it and the sky. That's usually enough to say whether a succulent will hold its shape there or slowly stretch out of it.

Which way does its window face?
Which hemisphere are you in?
How far from the glass is it?
Anything between it and the sky?
What does the plant look like right now?

After you grade the spot

Stretching is too slow to see. Succulent makes it visible.

  1. The checker grades the spot. Which window, how far back, what’s in the way — hold its shape, or slowly stretch.
  2. File the plant under where it actually stands. Windowsill, balcony, shelf — so the spot and the plant stay connected.
  3. Snap a photo now and then. Every photo is dated and kept, so you can scroll back through months of one plant and catch the drift while there’s still nothing to fix.
Succulent collection grouped by spot: Favorites, Windowsill and Balcony
Grouped by spotWindowsill and balcony plants kept apart, like this checker does.
Succulent add-record card for a Pachyphytum noting three new pups along the back edge, dated and tagged Windowsill
A dated line when it changes“Three new pups along the back edge” — or the first stretch.
Succulent Time Machine with a March before photo beside a September after photo
Spot the stretchThe first photo beside the latest, months apart.
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What "enough light" actually means for a succulent

Succulents come from bright, sun-drenched places, and a tight rosette is what a plant looks like when it has more light than it needs. When light is short, it does the only thing it can: it elongates, pushing the stem and leaves upward in a reach for more sun. That's etiolation — the gaps opening between leaves, the paler colour, the lean toward the glass.

So this checker isn't grading your décor. It's answering one question: is this spot likely to deliver the several hours of bright, direct light that keeps a rosette compact — or is it the kind of place where the plant slowly loses its shape?

Where the ranking comes from

The window order is the one in our guide, Why is my succulent stretching?: a south- or west-facing sill is ideal, and most succulents want several hours of bright, direct light a day. An east window gives real sun but only the weaker morning half of the day; a north-facing one gives no direct sun at all. If you're in the southern hemisphere the checker mirrors that — north-facing becomes the strong window.

Distance from the glass and anything blocking it are adjustments on top, and they're an estimate rather than a measurement. They're in there because the same guide says to move the plant to your brightest window and to place a grow light fairly close to the plants — light falls away sharply as you step back from a window, far faster than your eyes suggest, because your eyes adapt and a plant's chemistry doesn't.

The tool keeps its score to itself on purpose. It ranks spots against each other; it isn't a light meter, and printing "63 out of 100" would dress up a judgement as a measurement.

If you're not sure, move it up gradually

The two mistakes here aren't symmetrical. Too little light costs you shape — slow, permanent, but never fatal. Too much light too suddenly costs you leaves: a plant that has spent months in a dim corner can scorch in a couple of afternoons on a hot south sill, and burnt tissue doesn't heal either.

So when the verdict says to move it, move it in stages — an hour or two of direct sun a day at first, built up over a week or two. And rotate the pot every few days, or the plant will grow lopsided toward the light instead of evenly around itself.