Here are a few top tips to help you NOT kill your plants!
Don't over sow- being heavy-handed with sowing is one of the worst things you can do. It can sometimes feel like a good idea to sow lots of seeds in a tray in the hope that some will germinate, but when you over sow the seedlings get crowded and can not get enough water, light and air space to grow in the best way. Sow thinly!
Don't over water- again, it can be tempting to give seedlings all the water in the world, hoping that this will help them survive. However, too much water can rot seeds and suffocate the roots so the seedlings can't breathe. The top tip here is to dip your finger into the soil around the seedling to see if the compost is wet underneath- if it is then don't over water!
Don't under water- one of the quickest way to kill your seedlings is not watering your seedlings- especially in hot weather. When seedlings dry out this can cause irreparable damage, so if you're going away in the summer or in hot weather, ensure you ask someone to water your plants!
Pot on at the right time- leaving seedlings to grow in trays or small pots means they can become congested and that means there is less air flow which can encourage disease, plus they're fighting for light and nutrients and water which can stunt growth. You want to ensure you 'prick them out' and 'pot them on' at the right time (usually when the second set of leaves has grown- often called 'true leaves').
Hold by the seed leaves only- the seed leaves are the first two leaves you usually see when a seedling grows, then the second set of leaves are called the 'true leaves'. The first leaves are there to help the seedling grow and therefore when you are pricking out or potting on plants you should always hold the seedling by the seed leaves as it isn't so bad if these get damaged or snap. Never hold a seedling by the stem, because if it snaps there is nothing you can do to help the seedling continue growing, whereas a snapped seed leaf isn't the end of the world because the true leaves are still there!
Label everything- This is so important and HIGHLY underrated! Make sure you add the date you've sown or planted and the variety on every single pot if not you will get confused. It also helps you to know when to pot on and prick out seedlings too!
Harden off- this is particularly true of plants such as Sweet Peas or Ammi majus which might have been growing in a greenhouse or on a windowsill for a long time. By hardening off, you place the seedlings in pots outside during the day and then bring them indoors during the night. This helps them get used to the wind and outside temperatures and helps them acclimatise to them. Lots more info on this to come in Spring before we plant our seedlings into the ground!
I hope these tips helped a little with how NOT to kill your seedlings! If you have any questions then you can always send me a message and I'll be happy to help!