Quick Facts

Quick facts

• Originally from  Southern Europe and North Africa, Fennel (Foeniculum vulgare) is a tall biannual herb normally 1-2 meters tall sometimes reaching  to 2.5 metres found in cool to warm temperate, to humid climates.
• Leaves much divided and fine to 500mm long, small yellow flowers in clusters at the end of stems in umbrella-like heads.
• Grown world wide as a culinary herb and is generally not considered poisonous to humans or stock.
• It is a major invasive weed of disturbed areas particularly road, rail and water ways, were it smothers native vegetation.
• It spreads effectively from seed and plant segments moved via cultivation in soil or on machinery.
• Timing of the application of control methods is important for effective removal of this plant.
• Control plant when young before flowering.

What Does It Look Like?

What is it?

Fennel (Foeniculum vulgare) is an erect biennial or rarely annual herb that grows up to 2.5 m high with a stout, branched taproot. It is recorded as a perennial herb by Parsons & Cuthbertson (2001) with the rootstock remaining and resprouting after the above ground portion of the plant dies off (Cunningham et al. 1992).  It has a strong aniseed scent, with plants usually glabrous (smooth without hairs). The stems are robust and striated (striped with parallel, longitudinal lines or ridges), inside with white spongy pith. The leaves are 30-50 cm long, alternately arranged, and appear feathery because of many thread-like segments that repeatedly dissected, segments 0.5–8 cm long, to c. 0.5 mm wide. The petiole (leaf stalk) is hollow.

The inflorescence (flowering head) is a compound umbel (numerous aggregates of smaller umbrella-like arrangements of flowers originating from central point on flower stalks, each umbel originating from a central point). The large compound umbel of inflorescences are arranged at the end of the branches on a peduncle (main flower stalk holding inflorescence), to 12 cm long. Each compound umbel is 7-15 cm in diameter. Each smaller umbel is held on a secondary flowering stalk (ray) to 70mm long, with each small umbell 5–15 mm diameter, made up of 10-30 flowers, on pedicels (flower stalk to which the flowers are attached) 1–7 mm long. The petals are yellow and about 1 mm long sitting on top of the small, flattened and ribbed ovary.

The fruit is 4-7 mm long with 2 flattened sections which have 5 prominent equal ribs. (Cunningham et al. 1992;  eFloraSA 2021; Parsons & Cuthbertson 2001; PlantNET 2021; VicFlora 2016).

For further information and assistance with identification of Fennel contact the herbarium in your state or territory.

Flower colour

Yellow

Growth form (weed type/habit)

Herb

Where it currently grows? Preferred habitat

Fennel grows in temperate regions with a moderate rainfall on a wide range of soil types. It prefers open situations such as along railway lines or roadsides, channels and drains, and neglected areas (Parsons & Cuthbertson 2001). Fennel invades dry coastal vegetation, lowland grassland and grassy woodland, riparian vegetation and rock outcrop vegetation (Carr et al. 1992). IT has even been found in dry arid situations (eFlora 2021), but is rarely found in dry arid environments (AVH 2021). 

Are there similar species?

Wild Carrot (Daucus carota) which is common on roadside may be confused with Fennel. It has similar umbrella shaped heads of white or pinkish flowers, but the crushed leaves smell carroty and not of aniseed.

Hemlock (Conium maculatum) is another weed in the same family which is poisonous to humans and livestock. It differs from Fennel by having white flowers and the stems are hollow. It does have a strong odour, but it is not of aniseed (Cunningham et al. 1992; Walsh & Entwisle 1999).

Aniseed plant (Pimpinella anisum) has a similar aroma and is in the same family.

Why Is It A Weed?

What are its impacts?

Fennel (Foeniculum vulgare) impacts cool to warm temperate, and humid areas, growing in native vegetation and agricultural areas. It also is a weed of roadsides, railways, stream banks, alluvial flats, irrigation channels, gardens, refuse sites and disturbed areas, particularly in suburban areas. Strongly smelling of aniseed, some people consider the plant to have an offensive or even nauseating smell. Fennel is able to successfully compete with other vegetation once it is established, and may form dense stand excluding all other vegetation.

Agriculture: Commonly occurs in agricultural areas. Although not always considered palatable by animals, sheep and cattle may graze young plants, fennel can invade agricultural areas, particularly degraded pastures, with Queensland Government (2016) documenting it as palatable to livestock and is generally not seen as a major problem in these areas. However, Parsons & Cuthbertson (2001) comment toxicity problems in grazing animals are generally not encountered but deaths of both sheep and cattle have previously occurred after eating residues from distillation of commercially grown fennel plants. The grazing of Fennel stubbles do not appear to be toxic and it is rarely if ever a problem in field situations.

Native ecosystems: Impacts on vegetation found along road, rail and water ways potentially preventing native plant species from establishing or shading out existing plants. This could be of great significance in farming areas when remnant vegetation is often restricted to road and rail verges. Found in open woodland  especially along tracks and paths and the edges, and in open areas especially grasslands. 

Urban areas: A weed of urban areas, colonises gardens, abandoned and little carried for sites. Dense infestations along waterways may restrict some recreational activities (Muyt 2001).

How does it spread?

Fennel is spread mainly via its seed, however, pieces of root and crown that have been moved to other areas via cultivation machinery will resprout and establish. Seed contaminated agricultural produces, vehicles, machinery, stock, clothing, gravel, mud and water facilitate the spread of Fennel (Parsons & Cuthbertson 2001), and as a contaminant of gravel and land fill.  Seed  naturally disperse over 200 m from the parent plant (Blood 2001). Long distance dispersal and spread by water is particularly important occurring along waterways and drains (Parsons & Cuthbertson 2001).

What is its history in Australia?

Fennel has been a culinary plant for hundreds of years, all parts of the plant being edible. Seed is reputed to have been in the inventory of seed brought to Australia in 1788 by the first fleet and it was recorded as being sown in the Colony of New South Wales in 1803 (King 1803). By the 1880s it had become naturalised in many parts of New South Wales. It is cultivated as a crop, particularly in Tasmania (Parsons & Cuthbertson 2001).

How To Manage It?

Best practice management

Fennel (Foeniculum vulgare) is easily controlled when young before the plant elongate and grow a tall flowering stem. Treatment should occur when the plants are young , when they can be easily removed or are susceptible to herbicides. Mature plants are persistent and difficult to eradicate (Western Australian Herbarium 1998-).

Chemical control: Spot spraying should be carried out on actively growing young plants before they elongate and reach flowering stage, preferably with a selective woody weed herbicide. If the plants are growing near sensitive vegetation, they can be treated by the cut and paint method in winter-spring before new growth emerges. Make the cut close to the base or plants will re-sprout. Dense infestations can be slashed or burnt in winter to provide access for spraying in spring. Wild Fennel may sometimes be harvested by people for culinary use, so if spraying in public places, use a dye in the spray, and place a sign indicating that the plants have been sprayed (Parsons & Cuthbertson 2001). Follow up control of seedlings is required. Combination of burning followed by spraying may be effective for mature plants.

Please see the Australian Pesticides and Veterinary Medicines Authority for chemical information http://www.apvma.gov.au 

Non-chemical control: Physical control: Removing individuals of small plants or infestations of fennel is recommended with young plants hand chipped. To avoid cultivated forms of fennel becoming weed escapees remove spent flower heads before seed set. Fennel roots and foliage should be disposed of in hot composts to avoid unintentional vegetative or seed propagation (McFarlane 2007).  However, care should be taken if digging out mature large plants as Fennel is deep rooted, it can regrow from pieces left after cultivation.

Mechanical control: Slashing just before flowering may kill the plants, or repeat slashing of regrowth may be needed. At worst, slashing stems at flowering time will prevent seed set and buy a little time before the whole plant needs to be treated. . 

Does it have a biological control agent?

NO

When does it grow? (lifecycle/growth calendar)

Fennel generally does not flower until the plant is at least 18 months old. Flowering stems are produced from the crown of established plants each spring. Flowering begins in approximately November (late spring to summer) and continues until autumn. Seeds will germinate at any time with the right conditions. The flowering stems die back in winter and new leaves form from the crown in late winter (Cunningham et al. 1992; Parsons & Cuthbertson 2001).

Where Is It Found?

Which states and territories is it found?

ACT, NSW, QLD, SA, TAS, VIC, WA

What areas within states and territories is it found?

Fennel is found in the Australian Capital Territory and in the north and central coastal areas of New South Wales (PlantNet 2021).

In Queensland Fennel occurs in the south eastern corner concentrated around Brisbane (AVH 2021).c

In South Australia it is concentrated around the York Peninsula, Adelaide and Mount Lofty Ranges with scattered records from Kangaroo Island and the Eyre Peninsula (eFlora 2021).

In Tasmania it can be found across the whole state with concentrations around Hobart and Launceston (AVH 2021).

In Victoria it is concentrated around major urban areas from where it spreads along road and water ways (Victorian Resources Online 2007).

In Western Australia it occurs along the south- west coast from Perth to Albany (Western Australian Herbarium 1998- ).

Where does it originate?

Fennel is native to southern Europe, northern Africa and western Asia.

National And State Weed Listings

Is it a Weed of National Significance (WONS)?

NO

Where is it a declared weed?

TAS, VIC

Government weed strategies and lists – Weeds Australia

Is it on the National Alert List for Environmental Weeds?

NO

Government weed strategies and lists – Weeds Australia

Is it on the Agricultural Sleeper List?

NO

Government weed strategies and lists – Weeds Australia

Names And Taxonomy

Main scientific name

Foeniculum vulgare

Other scientific names (synonyms)?

Foeniculum officinale All.

Does it have other known common name(s)?

Anise, Aniseed, Aniseed Weed, Dill, Sweet Anise, Vinke, Wild Fennel.