I read the All About Growing Celery article (December 2011/January 2012). I use the ‘52-70 Utah’ variety and get celery all summer for the house and Saturday market.
I don’t find planting in trenches or flooding necessary, as the article suggests. I gently tie the stalks together with macramé yarn when they are 10 inches tall or so, then water well and mulch the soil generously. I enjoy my fresh harvests all summer.
When frost threatens, I dig up the remaining plants, heel them into the soil in the greenhouse and water well, which continues to provide me with celery until the end of December when I let the greenhouse freeze out.