While nigella sativa is sometimes referred to as "fennel flower", this is one of many misnomers. Nigella and fennel are not the same plant, nor are they closely related. Nigella belongs to the Ranunculaceae family of flowers, along with flowers such as delphinium and buttercup. On the other hand, fennel is in the Apiaceae family, which also includes flowering plants such as carrots, celery, dill, and parsley.