Is it hard to grow celery?
I think celery growing requires a knack and I don't have it. Instead I grow cutting celery (http://www.barbarapleasant.com/cuttingcelery.html) and celeriac (http://www.vegetablegardener.com/item...). I also found celeriac to be much easier to store for a much longer period of time than celery.
Here are some tips on growing celery:
I gave up on it some time ago since it seemed more trouble than it was worth for the little bit we used each year. I liked the related variety par-cel (as it sounds, a combination of parsley and celery) a little better.