General: Sweet Fennel is a short-lived perennial in the Apiaceae (carrot) family.
Flowers: In mild climates, Sweet Fennel may not bloom until its second year. The small, bright yellow flowers are produced in an umbrella-shaped cluster (umbel). Each umbel section has 20-50 flowers.
Stem: Each plant has 10 – 20 upright, jointed and hollow stems that originate from a basal cluster. Stems can reach up to 2 m in height and smell strongly of licorice and anise.
Leaves: Smooth, dark green leaves are finely dissected with very narrow lobes, giving a feathery, lacy appearance to the foliage. Leaves also smell like licorice and anise.
Fruit: Are elongated (3.5 – 4mm), dark green to brown (turning grey when dried) and longitudinally ridged.
Roots: Plants produce a large, deep, white taproot.
Poison hemlock (Conium maculatum): Sweet Fennel has a definite licorice scent and no purple spots on the stalks. Conversely, Poison Hemlock does not smell of licorice but does have purple blotches. Poison Hemlock flowers are white, whereas Sweet Fennel’s are yellow.
Habitat and Origin
Sweet Fennel is native to southern Europe and the Mediterranean region, where it has been used for centuries as a spice. The cause or date of its introduction to North America is unknown.
Sweet Fennel requires full sun and prefers well-drained soil. It often inhabits disturbed areas, so you are likely to spot Sweet Fennel along roadsides, pastures, prairies, streams, coastal bluffs, and wetlands.
Propagation & Vectors of Spread
Ecological, Economic, & Health Impacts
- Spreads aggressively, displacing native vegetation and dramatically altering the composition of many plant communities.
- Develops dense stands that have the potential to alter fire regimes, as dried plants facilitate the spread of fire.
- Can cause dermatitis if skin is exposed to sunlight following contact with the plant.
What Can I Do?
Sweet Fennel is not yet found in the Sea to Sky region, but is found in neighbouring areas and may arrive here soon. The goal is to prevent Sweet Fennel’s introduction by focusing on education and awareness. If prevention fails, the goal will become immediate eradication following the proposed SSISC EDRR protocol.
Learn to identify Sweet Fennel: use the images presented on this profile page to learn how to identify Sweet Fennel.
What to do if you spot it: You can report any Sweet Fennel sighting by visiting our reporting page.
- Regularly monitor properties for weed infestations.
- Ensure soil and gravel are uncontaminated before transport.
- Ensure plants are disposed of in a garbage bag if found in floral arrangements to prevent seeds from spreading.
- Unload, park or store equipment or vehicles in infested areas; remove plant material from any equipment, vehicles or clothing used in such areas and wash equipment and vehicles at designated cleaning sites before leaving infested areas.
- Plant Sweet Fennel in a garden, no matter how well-contained its enclosure may seem.
- Move soil that has been contaminated with Sweet Fennel.
- Compost Sweet Fennel!
- Seedlings and small plants can be dug out, but crowns and taproots must be removed to prevent regrowth.
- For larger infestations, plants can be repeatedly cut before flowering. This treatment may take several years to be successful.
- Be advised that Sweet Fennel can cause dermatitis if skin is exposed to sunlight following contact with the plant. If handling Sweet Fennel, wear gloves and long sleeves.
- Glyphosate, triclopyr, 2,4-D are effective against Sweet Fennel.
- We recommend that any herbicide application is carried out by a person holding a valid BC Pesticide Applicator Certificate. Before selecting and applying herbicides, you must review and follow herbicide labels and application rates; municipal, regional, provincial and federal laws and regulations; species-specific treatment recommendations, and site-specific goals and objectives.
- There are currently no available biocontrols in British Columbia.
- California Nature Plant Society, Fennel, https://cnpsslo.org/2018/12/invasive-species-report-fennel-foeniculum-vulgare/
- Centre for Agriculture and Bioscience International, Foeniculum vulgare (fennel), https://www.cabi.org/isc/datasheet/24271#topreventionAndControl
- Invasive Plant Atlas of the United States, Fennel, https://www.invasiveplantatlas.org/subject.html?sub=5648
- Invasive Plants of California Wildlands, Foeniculum vulgare, https://www.cal-ipc.org/resources/library/publications/ipcw/report51/
- Washington State Noxious Weed Control Board, Common Fennel, https://www.nwcb.wa.gov/weeds/common-fennel
- Whatcom County Noxious Weed Control Board, Common Fennel, https://www.nwcb.wa.gov/images/weeds/Common-Fennel_Whatcom.pdf