spindly cosmos seedlings

This is a completely novice question, so forgive me. I sowed some mixed cosmos seed at the beginning of April, at the same time as some marigolds. They have been in the warm with lots of light on a windowsill. The marigolds have grown into lovely little sturdy plants, but the cosmos have shot up (about 2 1/2 to 3 inches tall) to become thin and leggy, and although they each now have 2 pairs of leaves they are bending over and can't stand up under their own weight. They can't cope with a fine-rose watering can and a single raindrop would flatten them! What have I done wrong? And can I retrieve the situation?

Any advice greatly appreciated! Many thanks.

You will need to get them outside to harden them off and give them better all round light.

What you can do is, when you prick them out-bury the seedlings a bit deeper

It is basically caused them being too warm and in low light conditions-this should help

Thank you! I have been holding off putting them outside because it's been so cold, but I will get them out straight away.

Thanks for the advice geoff I have a similar problem, I have buried them deeper,and am now off to bring them in for the night as they are in pots in my shed,

                                                   Joan

I had the same problem and just potted them on, buried up to their necks and put them outside in a grow house, they're doing fine now

Having left them outside during the day for the last week, and spent the weekend repotting them much deeper, they now look much happier. I might have cosmos in my garden come the summer. Thank you sotongeoff!