I have just bought some sarah raven seedlings.
My previous plants have always become leggyand i have to stake them.
What do other gardeners do with there seedlings?
I start pinching cosmos back when they have 2 sets of proper leaves. This makes a bushier sturdier plant (still grow to about a metre high by the end of the season). I stop pinching back sometime in May and usually have flowers from August to last frosts.
This is for the ordinary bog standard large cosmos. The dwarf special varieties I grew one year didn't seem to like it so much.
When you prick them out, curl them around the pot so they are buried almost up to the first seed leaves.
then as TopBird says.
... that would be first frosts of course... duh!
Lyn is right about burying them deeply when potting on - I usually do mine a couple of times so I can plant out quite good sized plants.
My cosmos seeds will not germinate for some reason. Tried three or four times. Other seeds OK.