Your apartment is darker than it looks
Human eyes adapt so well that a room feeling “bright” often delivers a small fraction of the light a plant needs. A spot three metres from a window can receive less than five per cent of the light available on the sill itself. That is why leggy stems, tiny new leaves and a plant that has not grown in a year are the most common indoor complaints — and why a modest grow light is the single highest-impact purchase for anyone growing in a north-facing flat or a dim winter city.
Ignore the wattage on the box
Marketing wattage for LED fixtures is frequently the theoretical draw, not the real one, and neither number tells you what reaches the leaves. The figure that matters is PPFD — photosynthetic photon flux density — measured at the distance you will actually hang the light. Low-light foliage plants are content around 100–200 µmol; most tropicals thrive at 200–400; herbs, citrus and flowering plants want 400–600. Reputable manufacturers publish a PPFD chart at several heights. If a listing offers only “2000W equivalent” and a photo of purple light, treat that as a warning. A cheap phone light meter app will not measure PPFD, but it will happily show you that the shelf you thought was bright reads a tenth of the windowsill, which is usually the moment people stop arguing with the numbers.
Full spectrum white beats blurple
Those magenta panels work — plants use red and blue most efficiently — but they make your home look like a crime scene and your plants impossible to inspect for pests. Modern full-spectrum white LEDs cost the same, render foliage naturally so you can spot yellowing or webbing early, and grow plants just as well. For a living room, a warm white bulb around 3000–4000K in an ordinary clip lamp is both effective and unobtrusive. Keep bar-style fixtures for shelves and panels for dense plant walls. Look for a fixture with a decent aluminium heat sink rather than a bare plastic body: LEDs that run hot dim measurably within a year, and the cheapest strips are almost always the ones that fade first.
Distance is the dial you adjust
Light intensity falls off with the square of distance, so raising a fixture from 30cm to 60cm cuts what the plant receives to roughly a quarter. Start small foliage plants around 45–60cm below a bulb-style light and bring seedlings or succulents closer, near 25–30cm. Watch the plant: bleached, pale patches on upper leaves mean it is too close; stretched stems reaching upward mean too far. Adjust in ten-centimetre steps and give it two weeks before judging.
Twelve to fourteen hours, on a timer
Plants need a dark period to respire, so leaving lights on around the clock wastes electricity and stresses growth. Twelve to fourteen hours suits foliage plants; seedlings and herbs do well at fourteen to sixteen. A five-dollar mechanical or smart plug timer removes the decision entirely — set it once, and the routine survives holidays and forgetful weeks. Run it during daylight hours so the room still feels normal in the evening.
Light changes everything downstream
A plant under a good light photosynthesises faster, uses water faster and needs feeding more often. Expect to water noticeably more frequently once a fixture goes up, and to resume half-strength fertilizer through the winter when previously you would have paused. Watch for crisping leaf edges — extra light plus a heated room dries air quickly, and a pebble tray or a small humidifier keeps thin-leaved tropicals comfortable. Get those three things in balance and a dim flat stops being a limitation.