Celery seeds are the small brown seeds of the celery plant. They are known for their bitter smell and spicy taste. Celery seeds are often dried and used as a spice to flavor soups, stews, vegetable and meat dishes. They have been used in alternative medicine for centuries to treat colds, flu and poor digestion. Celery seeds contain calcium, boron, iron, zinc, and vitamins A, B-complex, and C.