leaf celery (par-cel) help please

You could thin to a small cluster of 3 or so and directly plant them outside as they're very hardy. Note that they are biennial...leaves this year, seeds next year.

Great herb, treat much like parsley, but let them grow a bit more before you plant out - the slugs love them!

I grow a lot of this cos I like a bit of celery flavour in stews and stocks, but whole heads are toooooo much.  As Trillium says they are hardy, and keep going and going as long as you are cropping.  Or you can chop and freeze leaves in ice cubes, stalks for stocks in a plastic bag.