U.S. DEPARTMENT OF THE INTERIORBUREAU OF LAND MANAGEMENT
 
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Sweet Fennel (Foeniculum vulgare)

Parsley/Carrot Family (Apiaceae)
 

Foeniculum vulgare (sweet fennel).  Photo courtesy of John M. Randall, The Nature Conservancy, Bugwood.org
Photo: John M. Randall, The Nature Conservancy, Bugwood.org

     Foeniculum vulgare (sweet fennel). Photo courtesy of John M. Randall, The Nature Conservancy, Bugwood.org    
Photo: John M. Randall, The Nature Conservancy, Bugwood.org

Foeniculum vulgare (sweet fennel).  Photo courtesy of John M. Randall, The Nature Conservancy, Bugwood.org
Photo: John M. Randall, The Nature Conservancy, Bugwood.org

Description/Habitat:  Sweet fennel (Foeniculum vulgare) is a perennial herb, 1 to 2 m tall with strong anise-like odor. It is native to southern Europe and the Mediterranean region, and has been used for medicinal and culinary purposes for many centuries. It has become naturalized in temperate areas around the world, especially in soils containing lime. After being established for cultivation in the early history of the United States it escaped to become a weed of waste places, roadsides, riverbanks, and other non-agricultural situations. How and when sweet fennel was introduced into California, where it is quite abundant in central and southern portions of the state, is still unknown.
 
Stems:  During the growing season the plant typically includes a mixture of living and dead, hollow stems (canes). Branches grow out from the stems at clearly jointed nodes, and leaves arise both from the root crown and from the stems. 10-20 stems originate from a basal cluster in late winter, then die back the following September-November.
 
Leaves:  Petioles are 7-14 cm long, and hug the stem. The leaf blades are triangular-ovate in outline and between 10 - 60 cm long and 30-40 cm wide, and are displayed in finely-dissected thread-like segments.
 
Flowers:  Yellow and small (approximately 6 millimeters across) and are usually found clustered in round umbels. The umbels are typically four inches across.
 
Seeds:  Seeds of sweet fennel share the appearance of the fennel seed commonly used in foods: they are oblong, dorsally compressed, and ribbed.  They are between 2.5 - 4.5 mm long and display prominent ridges.   
 
Flowering Period: April – July       
 
Management:  On Fort Ord National Monument, treatment of sweet fennel is limited to removing the entire plant, including all root structure, from the soil with hand tools. This method works well due to the fact that all fennel infestations at Fort Ord are relatively small. Removal can be done at various stages in the plant’s life cycle because fennel is relatively easy to identify. Each plant that is removed will also have the flower/seed heads clipped to prevent the plant from setting seed while it degrades. This two-stage management approach reduces chemical use while eliminating possible reproduction through removal of root and seed structures. In places with larger infestations, herbicide treatments have been effective by reducing cover by 75%.
 
                                            
Sources:
 
"Fennel, Foeniculum Vulgare (Apiales: Apiaceae)." Invasive Species: Information, Images, Videos, Distribution Maps. Center for Invasive Species and Ecosystem Health. Web. 20 Dec. 2011. <http://www.invasive.org/browse/subthumb.cfm?sub=5648>.
 
"Cal-IPC: Foeniculum Vulgare." Cal-IPC: California Invasive Plant Council Home. California Invasive Plant Council. Web. 20 Dec. 2011. <http://www.cal-ipc.org/ip/management/plant_profiles/Foeniculum_vulgare.php>.
 
"Foeniculum Vulgare - Bugwoodwiki." Main Page - Bugwoodwiki. Bugwoodwiki. Web. 20 Dec. 2011. <http://wiki.bugwood.org/Foeniculum_vulgare>.

 
Last updated: 08-20-2012