The dill plant (Anethum graveolens) provides feathery green leaves for the dill weed herb, while the flat, oval fruits make the dill seed spice. It’s an annual herb related to celery that tends to replant itself and spread widely, which is good to know if you’re considering planting it in your garden. Dill seeds are used in seasoning, such as in pickles. Dill weed is delicate and works particularly well with eggs or in salads.