An interesting option is leaf celery, called Zwolsche krul in German, which produces only thin stalks, but lots of leaf, and has a stronger celery taste than the more common types. The stalks are substantial and crunchy enough to substitute for ordinary celery, but the great benefit to this herb is its strong taste which lends itself well to soups and stews.
It is, of course, biennial, so that in the 2nd year it will produce a large quantity of strong celery seeds.