Do you need one?
A grow light helps when your plants show signs of too little light and there’s no sunnier window to move them to. Common reasons:
- Your only windows face north (or south in the Southern Hemisphere).
- Trees, buildings or deep eaves shade your windows.
- You want sun-loving plants, like echeveria or living stones, somewhere away from a window.
- Winter days are short and dim where you live.
What to buy
- White, full-spectrum LEDs are the easiest choice. They give plants the light they need, and the plants still look normal to you. Purple or pink grow lights work too, but they make it hard to see the plants’ real colors, or spot problems.
- Pick a shape that fits your spot. Screw-in bulbs work in a desk lamp or clip lamp. Light bars or panels cover a whole shelf.
- Skip incandescent bulbs. They give off a lot of heat and not much useful light.
- Get a plug-in timer. It makes the light turn on and off by itself, so you never have to remember.
How close?
Light gets weaker quickly as you move away from it, so distance matters a lot.
- Start about 6–12 in (15–30 cm) above the tops of the plants for most household LED bulbs and bars. Stronger panels may need more distance, so check what the maker recommends.
- Too far: new growth stretches, leans or turns pale green. Move the light closer.
- Too close: leaves bleach, turn red-brown, or get dry, crispy patches. Move the light farther away.
When you first put plants under a light, start at the far end of that range. Bring it closer over a week or two, just as you would ease a plant into stronger sun.
How long?
- Run it about 12–14 hours a day. A timer keeps this steady.
- Don’t leave it on all the time. Plants need a dark period each night too.
- Some plants flower only when nights are long. Flaming Katy and Christmas cactus need long, dark nights in autumn to set buds. Keep them away from a light that runs into the evening during that time.
Using a grow light safely
- Don’t stare into the light. Bright LEDs are hard on the eyes. Aim the light at the plants, not at your seat.
- Keep cords and plugs away from water when you water the plants.
- Check for heat. If the light feels hot on the back of your hand at the height of the plants, raise it.