6 tips to AVOID leggy seedlings (and 2 strategies to help if its already too late)
, by Ellen Rignell, 4 min reading time
It's March and we've had a dash of sunshine, so everyone's sowing seeds with wild abandon. How lovely!
But I'm worried.
Worried because these early sowings, while daylight hours are still limited, are at risk of getting leggy. By 'leggy' I mean the seedlings will have weak spindley stems, palid leaves and generally look a bit sorry for themselves.
Leggy seedlings don't usually thrive as well as healthy looking ones. Pests such as slugs and aphids tend to pick on them first. They also tend to flop over and rot at the stem if it's wet.
The good news is that if you grow your plants in a space designed for propagation (a bright greenhouse for instance), your seedlings will never be leggy.
'If only!' I hear you cry.
Yes, I know. Most of you will be using your brightest windowsill to grow your seedlings on. So I've put together 6 tips to help you grow the healthiest seedlings you can on your windowsill.
And if it's already too late and you need some strategies to coax your seedlings back into good health, there's a couple of pointers for you too.
1. Wait
I know it's boring and I don't mean to be a Spring Grinch but pushing sowings a little later is one of the best ways to avoid leggy seedlings, particularly if you're growing your plants on a windowsill. My advice is to avoid sowing anything until March, ideally until the second half of March. This is because there'll be more daylight towards the end of the month.
2. Turn your seedlings 180 degrees daily
Plants grow and stretch towards the light, if you turn your pots 180 degrees each day it keeps seedlings straighter and stops them keeling over.
3. Use reflective backing
Cover a piece of cardboard with tin foil and fix it behind your pots, this helps bounce the light around and means you don't need to turn seedlings so regularly.
4. Stroke your seedlings (or use a fan)
Sounds weird but it works. Gently run your hand over your seedlings every day, they like to be buffeted around a bit. In response, they'll grow sturdier stems and roots, setting them up well for life in the soil. You can also run a gentle fan at them or open the window a crack and it does the same job.
5. Keep them cool
Many seeds like warmth while they are germinating but as soon as they emerge, they benefit from cooler temperatures. If I was to explain it in a formula it would look like this:
Warm temperatures + short daylight hours = leggy seedlings
Cool temperatures + short daylight hours = healthy seedlings
Early on in the year, daylight hours are still limited so you want to keep your seedlings on the cooler side of things, particularly at night. For most things, 21C in the day and 15C at night is ideal.
6. Use 'seedling' compost
'Seedling compost' is lower in nutrients than 'potting compost' which is formulated for mature plants. Excess nutrients encourage sappy, leggy growth so it's important that you get your seedlings off to a good start in a low nutrient seedling compost.
So those are my tips for preventing seedlings from getting leggy in the first place, but maybe it's already too late? If it is, here are a couple of remedial strategies:
Pinch out
For some plants, you can pinch off the growing tip to encourage bushy side shoots. It's worth trying with flowers like cosmos, phlox, sweet peas, calendula, floss flower, snapdragons, ageratum, zinnias and vegetables like peppers, broad beans, basil and determinate tomatoes.
WARNING: pinching out seedlings in some crops can result in no crop at all - you wouldn't want to pinch out lettuce, onions, or sweetcorn for instance. And avoid pinching out single stem varieties of flowers like stocks, sunflowers and poppies.
Bury the stem
Some plants are capable of growing roots directly out of their stems. I think this is so cool. Sunflowers, tomatoes and peppers/chillies are particularly good at it. For these plants, if your seedlings are leggy, you can simply bury the stem in the soil (or pot), removing any unwanted leaves as you go. The plants will then form lovely strong root systems, directly from their stem.
WARNING: this only works for a few plants, the majority will take umbrage if you bury their stem. In most cases, it'll cause the plants stem to rot (unless they're one of the cool plants I've mentioned above).
I hope this helps you to grow some healthy seedlings this Spring!
