Dill is NOT a perennial.
More Info: Perennials are plants that survive more than two years. Dill is a tender annual surviving only one season.
The Origins of Dill
The name dill originates from the Norse word dylle, meaning to soothe or lull. Though the plant has no known sedative effects, the name may have originated from its common medicinal use of relieving colic in babies. Popular in England, dill is commonly used medicinally to make ‘gripe water’, which is said to relieve colic, a digestive aid, and to relieve bowel disorders. [“Dill” Biomedical Library History and Special Collection]
Why Is Dill Often Called a Perennial?
Dill is self-seeding. This means that once the seeds have formed, they will eventually drop and start new plants. So even if you don’t plant dill the next season, you may find that you have a new crop growing. The problem with self-seeding plants is that you have little control if any, where the seeds are dispersed and will germinate, so many people consider the plant a bothersome weed.
“Dill.” Biomedical Library History and Special Collection. UCLA, n.d. Web. 25 May 2012. <unitproj.library.ucla.edu/biomed/spice/index.cfm?displayID=10>.
Janssen, Don, and Extension Educator. “Growing Herbs.” University of Nebraska–Lincoln Extension in Lancaster County. N.p., n.d. Web. 22 May 2012. http://lancaster.unl.edu/hort/articles/ 2005/GrowHerbs.shtml
“Dill: Planting, Growing, and Harvesting.” Old Farmers Almanac: weather forecasts gardening moon calendar recipes. N.p., n.d. Web. 22 May 2012. <http://www.almanac.com/plant/dill>.