Leggy, pale, floppy seedlings are almost always a light problem, not a water or feed problem. A sunny windowsill simply isn’t bright enough for most seedlings — they stretch toward the glass and grow weak. A grow light fixed close above the tray gives strong, even light for the 14–16 hours seedlings want, producing short, stocky, sturdy transplants. This guide covers the grow-light types for seed starting and how to set them up.
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Quick recommendations
- Best all-round: a full-spectrum LED grow-light bar or shop light over the tray
- Best complete setup: a grow-light stand/rack with shelves
- Best small/space-saving: a clip-on gooseneck LED for a single tray
- Essential add-ons: a timer and an adjustable way to raise the light
How we chose
Seedlings need bright, even light held very close, with the ability to raise the fixture as they grow, plus a long daily run time. We favour full-spectrum LED bars and stands that deliver strong light across a whole tray. Based on seed-starting practice, not lab testing.
Recommended options
LED grow-light bars / shop lights
Bright, even coverage across a seed tray, hung on adjustable chains or stands so you can keep them close and raise them as seedlings grow. The workhorse of seed starting.
Grow-light stands & racks
A shelf unit with built-in lights is the tidiest way to start many trays, especially if you sow every year.
Clip-on gooseneck LEDs
For a single tray on a countertop; adjustable and cheap, with a built-in timer on many models.
Timers
Seedlings want a consistent 14–16 hour “day” — a plug-in timer makes it automatic.
Seed-starting light rules
| Factor | Do this |
|---|---|
| Distance | Keep the light close (a few inches / several cm) above the seedlings |
| Duration | 14–16 hours a day on a timer |
| As they grow | Raise the light to stay just above the tops |
| Windowsill only? | Usually too dim – expect leggy seedlings |
How to set it up
- Hang the light close — seedlings want it just above the leaves; too far and they stretch.
- Run 14–16 hours on a timer for strong, stocky growth.
- Raise the light as the seedlings grow to keep the gap small.
- Add gentle airflow (a small fan) for sturdier stems and to reduce damping-off.
Common mistakes
- Relying on a windowsill — the number-one cause of tall, floppy seedlings.
- Hanging the light too high, so seedlings stretch toward it.
- Too few hours; seed starting wants a long day.
- Not raising the light as plants grow, so tops get scorched or shaded.
FAQ
Why are my seedlings tall and leggy? Too little light — usually a windowsill. Put a grow light close above them and run it 14–16 hours a day.
How close should a grow light be to seedlings? Close — a few inches / several centimetres above the tops — and raised as they grow.
How many hours of light do seedlings need? About 14–16 hours a day on a timer for strong, stocky growth.
Can I use a normal LED shop light? A full-spectrum LED shop light works well for seed starting; the key is keeping it close and running it long enough.
Final recommendation
For seed starting, a full-spectrum LED bar or shop light held close above the tray and run 14–16 hours on a timer produces short, sturdy seedlings every time — step up to a grow-light stand if you start many trays. Raise the light as they grow, and skip the windowsill.
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See also: grow lights for indoor plants · all grow lights.