Or prevent it from happening in the first place
Disaster – your carefully nurtured seedlings have turned into drawn, thin, spindly beings, all pale stem and hardly any leaves. Here’s how to fix leggy seedlings.
It happens to the most experienced gardeners, especially if you’re trying something new. You see here my tomatillo seedlings, which quickly flopped but came through in the end. These are the main causes of weak, elongated stems:
Too much heat
- The top three here are almost always linked and usually happen to eager beavers who can’t wait to get started. Maybe you’ve just bought a heated propagator.
- One thing I fell foul of was growing super-hot chillies, which needed to be started early at a high temperature. They were fine, but the tomatillos I sowed in the same propagator became leggy. They put on an unnatural growth spurt, stretching up to reach the light.
- Prevention: Always sow at the temperature recommended on the packet – too hot can be as damaging as too cold.
How to fix leggy seedlings – Too little light
- The most common cause if you sow too early. They are struggling upwards to get as much light as possible, and then the stems become so weak that they can’t support the leaves.
- Prevention: Sow later or invest in a grow lamp. Seedlings will naturally lean towards the light, especially on a windowsill, so turn them every day.
- Use some aluminium foil or white reflective material behind seed trays to maximise light levels.
Sowing too early
- Without a grow light or propagator, you’re likely to fall victim to the above.
- Prevention: Wait a month to make use of the lengthening natural daylight. The seeds will grow stronger and more quickly.
How to fix leggy seedlings – Poor seed sowing compost
- Cheap or old compost saves you nothing in the end. Without the correct nutrition, seedlings become leggy even if light levels, etc, are good.
- Prevention: Buy good-quality compost – worth its weight in gold.
Lack of moisture
- If you forget to water, seedlings wilt quickly. This means they can’t access the nutrients they need, so they end up thirsty and starving.
- Prevention: Check every day and don’t let them get dry.
How to fix leggy seedlings – Still air
- Buffeted by the wind, outdoor seedlings grow strong, sturdy stems – in effect, resistance training! Seedlings grown inside are in a calm environment, so they are weaker.
- Prevention: Gently run your hands over the tops of the seedlings daily to strengthen stems.
How to fix leggy seedlings
My tomatillos recovered well after being potted on into a decent compost – bury the stems deep, as roots will form under the soil – tomatoes respond especially well to this. Keep them in good light, not too warm and brush your hand gently over the tops – within a week, they were putting on good leaf growth and weren’t bowing, sure signs of recovery.
However, if they are so weak that they prove impossible to pot on, cut your losses, throw them on the compost heap, sow again and put it down to experience. If you’re still stuck, the RHS has lots of information on seedlings.
Thank you for your tips about sowing seeds. I am sowing now in different places as experiments. I am using plastic box from old fridge as a cold frame in the backyard. I have them each protected by plastic bag as slugs can get in. I have some on inside windowsills. I have Aubrietia, Echinacea and Rudbeckia on the go. I am going to place some pots in the garden where I do the voluntary work. I will let you know the results. I think this is pot luck. John
Good luck John – I’ll reuse anything if it works!