California Invasive Plant Council

Foeniculum vulgare

Common names: fennel; sweet fennel; sweet anise

Foeniculum vulgare (fennel) is an erect perennial herb (family Apiaceae). Although the plant is very common throughout the state, dense local populations have been reported from Santa Cruz Island, in fields around the San Francisco Bay region, Palos Verdes Peninsula (Los Angeles County), and Camp Pendleton (San Diego County). It can drastically alter the composition and structure of many plant communities, including grasslands, coastal scrub, riparian, and wetland communities. It is still unclear whether culinary varieties of fennel are invasive.

Cal-IPC Rating: Moderate?

Explanation of Cal-IPC ratings

• High – These species have severe ecological impacts on physical processes, plant and animal communities, and vegetation structure. Their reproductive biology and other attributes are conducive to moderate to high rates of dispersal and establishment. Most are widely distributed ecologically.
• Moderate – These species have substantial and apparent-but generally not severe-ecological impacts on physical processes, plant and animal communities, and vegetation structure. Their reproductive biology and other attributes are conducive to moderate to high rates of dispersal, though establishment is generally dependent upon ecological disturbance. Ecological amplitude and distribution may range from limited to widespread.
• Limited – These species are invasive but their ecological impacts are minor on a statewide level or there was not enough information to justify a higher score. Their reproductive biology and other attributes result in low to moderate rates of invasiveness. Ecological amplitude and distribution are generally limited, but these species may be locally persistent and problematic.
• Alert – An Alert is listed on species with High or Moderate impacts that have limited distribution in California, but may have the potential to spread much further.
• Watch – These species have been assessed as posing a high risk of becoming invasive in the future in California.

CDFA Rating: None?

Explanation of CDFA ratings

• A – A pest of known economic or environmental detriment and is either not known to be established in California or it is present in a limited distribution that allows for the possibility of eradication or successful containment.
• B – A pest of known economic or environmental detriment and, if present in California, it is of limited distribution.
• C – A pest of known economic or environmental detriment and, if present in California, it is usually widespread.
• D – An organism known to be of little or no economic or environmental detriment, to have an extremely low likelihood of weediness, or is known to be a parasite or predator.
• Q – An organism or disorder suspected to be of economic or environmental detriment, but whose status is uncertain because of incomplete identification or inadequate information.
• * – An asterisk next to the rating indicates that a plant is included in the CCR Section 4500 list of California State Noxious Weeds.
• -* – This plant is included in the CCR Section 4500 list of California State Noxious Weeds, but is otherwise not rated.

More details

Assessment(s)

Plant Assessment Form - Information gathered by Cal-IPC on the impacts, rate of spread, and distribution of invasive plants in California. Does not include management information.

Species ID Card

Invasive Species ID Card - To support field identification of early detection species, Cal-IPC has designed a set of Species ID cards that can be downloaded, printed double-sided, and trimmed to size.

Weed Management Notes

• Management Notes - Information on management techniques and effectiveness from the University of California Cooperative Extension’s Weed Research & Information Center.

Cal-IPC Newsletter Articles

• East Bay volunteers head to the hills and the shores. Schwartz, Susan. Vol 16, Issue 4
• Don’t sell a pest: A new partnership to prevent plant invasions through horticulture. Connick, Sarah; Gerel, Mike. Vol 13, Issue 2
• An island called Santa Cruz: Removing invasives on the Channel Islands. Owen, Ken. Vol 12, Issue 2
• Teaching weeds: California university invasive plant programs. Cole, Kristie; Molinari, Nicole. Vol 12, Issue 2
• Viewing invasive species removal in a whole-ecosystem context. Zavaleta, Erika S.; Hobbs, Richard J.; Mooney, Harold A.. Vol 10, Issue 3
• Education: Wildland weed tours and talks. Kelly, Mike. Vol 08, Issue 1
• Roundup of Arundo projects reveals commitment, strategic weakness. Kelly, Mike. Vol 07, Issue 2
• Richmond weed abatement ordinance. . Vol 07, Issue 1
• Results of the CalEPPC questionnaire at Symposium ’98 in Ontario. DiTomaso, Joe. Vol 06, Issue 4
• Legendary stewardship award. Goode, Suzanne. Vol 06, Issue 2
• Highways as corridors of dispersal. Madison, John. Vol 04, Issue 1
• Exotic pest plants of greatest ecological concern in California September 1994. Cal-IPC. Vol 02, Issue 4

Cal-IPC Symposium Presentations

Presentations are linked where available. Where a presentation is not available, find more information by reading the abstract in the Cal-IPC Symposia Archive.

• Control of invasive plants after the Scorpion Fire on Santa Cruz Island. Woolsey, Jay; Parker, Mike; Carter, Katy; Little, Annie; Cowan, Clark (2022)
• A test of the herbicide Weed Slayer for the control of invasive plants. Thomas, Don (2020)
• Mapping weeds and rare plants to inform management and conservation in the Zaca and Jesusita fires. Calloway, Stephanie; Schneider, Heather; Knapp, Denise (2018)
• Native plant recovery in seeded and non-seeded plots following exotic fennel (Foeniculum vulgare) control on east Santa Cruz Island – ten years post treatment. Cowan, Clark (2018)
• Modeling the control of invasive fennel (Foeniculum vulgare) on San Clemente Island. Havstad, Emma (2017)
• Desire, disappointment, surprises, and food webs: melding conservation and ecological perspectives to better understand animal-invasive plant interactions. Klinger, Rob (2010)
• Weeds and wildlife, impacts and interactions: A case study from Santa Cruz Island, California. Morrison, Scott (2010)
• Assessing the effects of Foeniculum vulgare on seedling germination, soil legacy effects and restoration strategies. Liu, Heather (2009)
• Evaluating the seed bank of a disturbed site to determine potential ecological restoration strategies. Olesen, Cory; Doran, Daniel; D_Antonio, Carla (2009)
• Using airborne remote sensing to map sweet fennel on Santa Cruz Island (5.2). Dahlin, Kyla; Asner, Greg; Field, Chris; Shaw, Rebecca (2008)
• The cost and effectiveness of small-scale fennel control methods. Gwinn, Abigail (2006)
• The fennel battle on MCB Camp Pendleton: Partnerships and techniques in combating the invasion. Easley, Todd; Bieber, Deborah; Bell, Carl; Tomsovic, Pete (2005)
• Partnering to prevent invasions of plants of horticultural origin. Connick, Sarah; Gerel, Mike (2004)
• Use of fire to control French broom. Boyd, David (1995)
• Modeling the expansion and control of fennel (Foeniculum vulgare) on the Channel Islands. Brenton, Robert K.; Klinger, Rob (1994)

Other Foeniculum vulgare Information

• Bugwood - National database from the Center for Invasive Species and Ecosystem Health at the University of Georgia.
• CalPhotos - Images of plants taken mostly in California.
• Calflora - Distribution map and records of this species in California.
• CalWeedMapper - Distribution map of this species in California with ability to determine regional priorities.
• EDDMapS - Distribution of this species in North America.
• Jepson Interchange - Information on this plant's taxonomy, biology, and distribution from UC Berkeley's Jepson Herbarium.
• USDA PLANTS Database - Information on identification and distribution, with links to websites in individual states.

Additional photos