This is not a celery.
It is a cardone, which grower Ocean Mist is proud to tell me is an Italian favorite, although I’d never heard of it until I found it next to the leeks at the grocer. It’s supposed to be related to an artichoke, but it looks like the happy marriage of a celery and an aloe plant and tastes like bitter greens. Ocean Mist suggests brining it to get rid of the bitter, but I tried a piece raw and I didn’t think brining did anything terribly interesting to it. I like bitter greens undiminished and unadulterated, so your mileage may vary on that direction.
The brined version, getting a quick saute.
Unbrined as part of a ‘salad’ of nuked veggies. The brined got discolored, too, so I suppose treating it like chard and giving it a little lemon juice would work on the aesthetics, but I don’t mind discolored chard, either.