Celery

Here I go again!
I planted some celery seeds in a tray they are now up and looking ok but, what do I do next?
I lost the packet and can't remember what to do next.
cheers

 

I have a couple of library books out at the moment so I looked it up as I have never tried to grow celery.
The Allotment handbook by Caroline Foley says
When seedlings have 6 leaves harden off .If temp drops below 10c for any lengh of time they will bolt.Transplant cover with fleece or cloches for a few weeks,water in well.The self blanching ones are planted in a block to shade each other.The outer ones are given a collar cardboard covered in black polythene.The traditional way is to grow them in a trench and earth it upto keep the stems whole
Self blanching - seed to harvest 12- 16 weeks
Trench celery -Seed to harvest 9 months
Hope this is of some use.