Grow Lights for Indoor Plants: Which LED, How Close, How Long
Grow lights do work, and for most flats you do not need the purple panels sold online. A plain white “daylight” LED tube or bulb (around 6500K), placed close to the plants and run for 12 to 14 hours a day on a cheap timer, keeps herbs, seedlings and leafy houseplants growing in a room that never sees the sun. Distance matters more than brand.
Quick setup
- Light type: full-spectrum white LED, or a daylight (6500K) LED tube for herbs and greens
- Distance: about 6 to 12 inches above herbs and seedlings; 12 to 24 inches for foliage houseplants; farther for low-light plants
- Hours: 12 to 14 a day for herbs and seedlings; 8 to 12 for foliage plants
- Timer: a plug-in mechanical or digital timer; consistency beats remembering
- Running cost: watts x hours a day x 30 / 1000 = units (kWh) per month
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Do grow lights actually work for indoor plants?
Yes. Plants do not care whether light comes from the sun or an LED, only how much reaches the leaf and for how long. The problem in most apartments in Karachi, Lahore or Delhi is that a few metres from a window, natural light drops to a fraction of what even shade-loving plants want. A light placed close above the leaves makes up that gap. What a lamp cannot do is fix overwatering, cold draughts or a pot without drainage, so get those right too.
Full spectrum, purple or a normal LED: which is best?
| Light | Good for | Honest note |
|---|---|---|
| Daylight LED tube or bulb (about 6500K) | Herbs, lettuce, seedlings, foliage plants | Cheap, easy to find at any electric shop; must be close |
| Full-spectrum white grow LED | Everything, including flowering | Looks natural in a living room; costs more |
| Purple (red and blue) panel | Growing indoors where looks do not matter | Harsh glare; makes plants hard to inspect for pests |
| Warm white household bulb (2700K to 3000K) | Better than nothing | Weaker for leafy growth; fine as a top-up |
| Old incandescent bulb | Nothing | Hot and inefficient; can scorch leaves |
The colour figure on the box (kelvin, K) tells you how blue or warm the light looks. Cooler daylight light around 6500K suits leafy growth. If you want flowers or fruit indoors, such as chilli or a small tomato, a full-spectrum grow light gives better results than a plain tube.
The shelf trick that costs least
Fix two 18 or 20 watt daylight LED tube lights under a shelf or on a wooden frame, side by side, and hang them on chains so you can raise them as plants grow. A tray of dhania, pudina and lettuce sitting 6 to 8 inches below two tubes, run 14 hours on a timer, grows steadily even in a windowless kitchen corner. Paint the wall behind white, or line it with foil, to bounce light back.
How many hours should a grow light be on?
Most houseplant and herb guides land on 12 to 16 hours, with 12 to 14 a good everyday target. Plants also need darkness to rest, so do not run lights 24 hours.
- Seedlings and herbs: 14 hours.
- Leafy greens (lettuce, palak, dhania): 12 to 14 hours.
- Foliage houseplants (pothos, snake plant, ZZ, peace lily): 8 to 12 hours, as a top-up to window light.
- Succulents and cactus indoors: 12 to 14 hours, very close, or they stretch.
Put the light on a timer from, say, 7 am to 9 pm. Missing a day now and then is fine; irregular light every day is not. During load-shedding, a few lost hours do not matter much; plants simply grow a little slower.
How far should a grow light be from plants?
The light’s strength falls off quickly with distance, so a weak tube at 2 feet does little, while the same tube at 6 inches does a lot. Start with these and adjust:
- Seedlings and herbs: 6 to 8 inches below a tube, 12 inches below a stronger panel.
- Foliage plants: 12 to 24 inches.
- Low-light plants like snake plant and pothos: 18 to 36 inches, or simply beside a bright lamp.
- After a week, read the plant: pale, stretched stems with long gaps between leaves mean move closer or run longer; bleached or crispy patches mean move farther away.
- Touch the leaves under the light at the end of the day. Warm is fine; hot means raise it.
Grow light wattage and electricity cost
Wattage on the box is the electricity the light draws, not how bright it is for plants, and some sellers advertise inflated “equivalent” watts. Work out running cost from the real wattage:
- One 20 W tube x 14 hours x 30 days = 8.4 units (kWh) a month.
- Two tubes: about 17 units a month.
- A 45 W panel x 12 hours x 30 days = about 16 units a month.
Multiply by the per-unit rate on your own electricity bill to see the real cost. A small shelf of herbs adds a modest amount; a big panel running all year is a noticeable bill, especially in summer slabs.
Grow light price in Pakistan and India: what to look for
Prices change too often to quote, but the rule is simple. Ordinary daylight LED tubes from an electric shop are the cheapest route. Branded full-spectrum bulbs cost more but look better in a room. Avoid cheap purple panels with exaggerated wattage claims and no brand. Look for the real wattage, the colour temperature (K), a proper earthed plug, and a warranty.
Which plants are worth growing under lights?
Herbs and greens are the best return: dhania, pudina, basil, lettuce and spring onion. Seedlings started in February under lights grow sturdy for spring planting. Foliage houseplants in dark rooms benefit too. Fruiting plants indoors are possible but demand strong lights and patience. For choosing plants that cope with little light in the first place, read our guide to indoor plants that survive in low-light flats and windowsill herbs in low light. More houseplant guides are in Phool aur Paudhe.
Water and electricity sit close together in a grow setup. Keep all plugs, timers and extension boards above the level of any tray, use an earthed socket, and never use cracked fittings or bare joints. Do not leave cheap unbranded panels running unattended near curtains or wooden shelves. Children must not be able to pull lights down on chains. Do not stare into bright LED panels; purple panels in particular cause eye strain, so switch them off while working on plants.
Grow light questions people ask
Do grow lights really work?
Yes, when they are close enough and on long enough. Most failures come from lights hung too far away.
Can I use a normal LED bulb as a grow light?
Yes, especially a cool daylight (around 6500K) bulb or tube, placed close to the plants. Warm white bulbs work less well for leafy growth.
How many hours a day should I leave a grow light on?
About 12 to 14 hours for herbs and seedlings, and 8 to 12 for foliage houseplants. Always give plants a dark period.
Can I leave a grow light on 24 hours?
No. Plants need darkness to rest, and continuous light can stress them. A timer keeps a steady day and night.
Are purple grow lights better than white?
Not for a home. White full-spectrum light grows plants just as well, looks normal, and lets you spot pests and disease.
Can a grow light burn plants?
Yes, if it is too close or too strong, leaves bleach or crisp. Raise it a few inches and check again after a few days.
How much electricity does a grow light use?
Multiply real watts by hours a day and by 30, then divide by 1000 for monthly units. A single 20 W tube for 14 hours uses about 8 units a month.
Do succulents need grow lights indoors?
Usually yes, unless they sit on a sunny sill. Indoors without strong light, they stretch and lose colour within weeks.