Why Are My Seedlings Leggy? Causes and Fixes
Owen Petrakis · Oct 19, 2026 · 5 min read
Quick answer
Tall, thin, floppy seedlings are stretching for light. You can rescue many of them and prevent it next time.
Leggy seedlings have long, pale stems and small leaves, and they often flop over. It is one of the most common problems when starting seeds indoors.
The main cause is not enough light, often combined with too much warmth.
1 What causes it
- ✓Light too weak or too far away — a windowsill in early spring is rarely enough
- ✓Temperatures too warm, which speeds growth beyond what the light supports
- ✓Seedlings sown too thickly, competing for light
- ✓Leaving seedlings under a propagator lid for too long after germination
2 Rescuing leggy seedlings
Tomatoes can be repotted deeper, burying most of the stem — they grow roots along it. Brassicas and many flowers can also be planted a little deeper. Move all seedlings to a brighter, slightly cooler spot straight away.
3 Preventing it
Use a grow light placed a few centimetres above the seedlings, raising it as they grow, and run it for around 12–16 hours a day. Remove propagator lids as soon as most seeds have germinated. A gentle fan or brushing your hand across the tops each day encourages sturdier stems.
4 Sow later
Sowing too early is a major cause of leggy plants. Check the seed packet and local last-frost dates; seedlings sown a few weeks later often catch up and end up stronger.
This is general gardening information. Results depend on your climate, soil, and conditions. Follow label directions for any fertiliser or treatment, and check whether plants are toxic to pets or children before bringing them home.