It's on the label of almost every houseplant you buy: "prefers bright, indirect light." And it tells you almost nothing, because nobody explains what it means. Is a windowsill too bright? Is the middle of the room dark? Here's the plain version, plus a ten-second test you can do with your own hand.
01The three levels, in plain English
Forget the jargon. Indoors, there are really only three kinds of light, and the difference is whether a beam of sun physically lands on the plant.
- Direct sun — an actual sunbeam falls on the leaves for part of the day. You can see the patch of sunlight move across the floor. Hot, intense, and enough to scorch many foliage plants.
- Bright indirect light — the room is genuinely bright and airy, but no direct beam ever touches the plant. Think of a spot near a window that the sun's rays skim past rather than hit. This is what most houseplants want.
- Low light — set back from windows, in a corner or an interior wall, where no direct sun reaches at all. It's dimmer than your eyes tell you; eyes adjust, plants don't.
02The shadow test
Your eyes are hopeless at judging light levels — they compensate automatically. Your hand doesn't lie. On a bright day:
- Hold your hand about 30cm above the plant's leaves.
- Look at the shadow it casts.
- Sharp, crisp-edged shadow = bright or direct light.
- Soft, fuzzy-edged shadow = bright indirect light. This is your target for most plants.
- Barely any shadow at all = low light.
Do it at midday for the truest reading, and remember light shifts through the day and across the seasons.
03Which UK window is which
Aspect makes a big difference in British light, which is gentler than many care labels (written for sunnier climates) assume.
- South-facing — the brightest, and the only one giving strong direct sun for hours. Wonderful, but fierce in summer. The RHS notes a spot in direct summer sun will often scorch leaves unless you filter it, so diffuse it with a sheer curtain and most foliage plants will love it.
- East and west-facing — the sweet spot. Bright for much of the day with only gentle, glancing sun. This is bright indirect light without you having to do anything.
- North-facing — cool and low. Fine for shade-tolerant plants, but the RHS points out north-facing sills get tricky in winter as days shorten.
The thing people most underestimate is distance. Light falls off fast as you step back from the glass — a plant "by the window" and one "across the room" are living in completely different worlds. The RHS is blunt that many plants struggle set back from windows. If in doubt, move it closer.
04Matching plants to light
- Happy in bright indirect light: most foliage plants, including calathea and monstera. Give them that soft-shadow spot near an east or west window.
- Tolerate low light: the snake plant and pothos will cope further from a window than most.
- Want direct sun: aloe vera and other succulents. These actively want that south-facing sunbeam — bright indirect isn't enough for them.
05The honest bit about "low light"
"Tolerates low light" means survives, not thrives. Almost every plant reaches towards the brightest light it can find; in a dark corner it stretches, the gaps between leaves lengthen, and the colour pales. That's not a happy plant — it's a coping one. The good news: it's usually reversible. A few weeks on a brighter windowsill and most plants perk back up.
You probably don't need a grow light for a normal bright room. The RHS advises using artificial lighting only where natural light is genuinely insufficient — a windowless bathroom, a dark corner, or short winter days for light-hungry plants. If you've a bright east or west window going spare, that's a free grow light already.
How we checked this
Every care and safety claim on this page is verified against horticultural and veterinary sources.
Sources: RHS — Choosing the best houseplants (light levels, window aspects, distance from windows, scorching) · RHS — Artificial lighting for indoor plants (when a grow light is and isn't needed)
Checked 2 August 2026. If our advice ever conflicts with the RHS, believe them and tell us.