It looks like bolting to me...probably as a result of a 'hobby' direction.

Celery needs an extra amount of water [muck ground the best] and slightly cooler temps.

bolted. plant it, next year the new plants from the seeds will give you usable celery, and this plant will flower and set seed again. I am overrun with volunteer celery, and it seeds prodigiously..

Thanks friends! Good to know.

LOribee Mine has gone to seed and is HUGE!!!!! Like 5 ft tall!
I don't know when to cut it or save the seed!
Usually I plant the end of a celery clump and keep it wet for a couple of weeks and it grows! Very strong tasting in my opinion, but great in soups/stews! Nancy

that is right, Nancy. Mine is very strong. One handful of it in the cavity of a chicken, with a tbsp of salt, and that is all it takes. the seed is tiny and you may find that, if you cut it, as you take it out of the bed it starts showering seeds all over. I have given up and I have one bed wild celery, and whack every other bed. It is a bad weed. My wife chops and freezes large pillows of celery for the winter. It goes in stocks, soups and stews, but also in juices.

I guess that I think differently than many here. If I had an unknown variety, why would I be saving seed. I would just order a suitable variety from a catalog. Someone help me out here.

I let my celery go to seed for the pollinators. It volunteered nicely the next year. I prefer cutting celery since it has lots of flavor for soups. I also grow regular but don't blanch. So much better than store bought, even if my stems aren't fat.