How to grow on your free seeds successfully

Seedlings are on a mission to grow, and under cover they’re relying on you. So check daily to make sure they have all they need.

Give seedlings plenty of light – but be ready to shade them with newspaper on hot days as intense sunlight scorches delicate leaves. Cold snaps also cause setbacks: watch the forecast and have heated propagators at the ready, or bring seedlings indoors temporarily.

Water daily if it’s sunny, but less often in cool spells. Always test first with a finger in the compost or by lifting up the tray: if it’s heavy, it probably doesn’t need watering. And don’t overdo it - if water runs out the drainage holes, it’s washing out nutrients too. So dampen the compost, then stop.

Pricking out

Once seedlings develop a second pair of leaves, they need their own pot - 7-8cm diameter for most, or 10-12cm for bigger courgettes or sunflowers. Second-hand clay pots, or biodegradable fibre pots are ideal.

Ease out a clump of seedlings with an old kitchen fork then gently separate them. Always handle seedlings by the leaves: if you tear a leaf, it’ll regrow, but break the stem and it’s game over.

Plant with the lowest leaves just above soil level. Don’t worry about burying the stem - this produces a sturdier plant.

Caring for newly pricked-out seedlings

Keep newly pricked out seedlings consistently damp and feed weekly using a general purpose liquid feed – seaweed or home-made nettle tea will keep your babies growing strongly. While seedlings are very small, dilute to half strength (nettle tea should be the colour of very weak tea). As they grow, increase the concentration to normal levels.

Potting on

Seedlings put on a real growth spurt once pricked out, so keep moving them into gradually larger clay or biodegradable pots to avoid their roots getting too cramped.

You’ll know they’re ready for a bigger pot if you see roots at the drainage hole or emerging from the sides of biodegradable pots, Once your youngsters are filling a 10-15cm container, as long as it’s warm enough outside they’re ready to plant out.

Hardening off

Moving seedlings from a warm sheltered greenhouse or windowsill into a chilly, breezy spring garden can be a shock. So it needs careful handling.
It takes up to two weeks for young plants to adjust. Move them to a cold frame at first, then start opening the lights (windows) daily, a little wider every few days. Or just move your plants into a sheltered spot outside for a little longer each day. This gives them time to toughen up, so when you finally do plant them out they hardly notice.

Caring for seedlings in the ground

Once direct-sown seedlings emerge, they should be easy to spot – they’re the ones growing in straight lines, unlike weed seedlings which will be dotted about. If you’re still unsure, wait till they produce adult leaves which are easier to recognise. Pinch out weed seedlings early or they’ll out-compete your seedlings for nutrients and water.

Just-emerged seedlings need daily watering unless it’s raining. In early spring, cover the row with a cloche against bad weather. Remove cloches as soon as it’s consistently warm enough for you to be outside without a coat.

Slugs adore newly-emerged seedlings and can be a menace. Check seedlings every evening, especially in damp weather, and remove any you spot. Protect individual sunflowers or courgettes with rings of bran or sheep’s wool pellets, or by covering with a cut-off plastic drinks bottle sunk into the soil. If all else fails, water with nematodes – these biological controls devour even tiny slugs before they cause any trouble.