Real celery can replace celery seed in a recipe. It can also be replaced with dill seed as well as celery salt.
Celery seed has a strong flavoring that comes in handy for a variety of recipes, including soups and stews. It is also used for pickling vegetables.
Celery seed offers a strong taste in dishes. If the celery seed is replaced by another herb or regular celery, use additional amounts of the replacement ingredient than what the original recipe calls for. If celery salt is the alternative ingredient, reduce the amount of regular salt in the recipe to prevent the dish from tasting too salty.