Celery has really shallow roots and loves lots of water, so will bolt fairly easily. So a mulch is very useful, compost on top is best imo. If on sandy soil you will need to water it daily
Try "Victoria" for a great self blanching one, it's noticeably better than any open pollinated selection I've tried to date. I sow mid march and mid May under cover in modules to extend the harvest time, I also dig out a couple in late autumn before any hard frosts and pot them up into my greenhouse. Still got a couple growing now as it's been so mild, probably only good for soup though! Also deer love it