Fennel is native to southern Europe and the Mediterranean region, where it has been used for centuries as a spice and for medicinal purposes (Garland 1979). Although details about its introduction are unknown, it has occurred in California for at least 120 years and is presumed to have escaped from cultivation repeatedly (Robbins et al. 1941).

Fennel will reproduce from both root crown and seed. Seeds are dispersed by water and on vehicles and clothing. Birds and rodents eat the seeds and may disperse them as well.