Foeniculum vulgare (fennel)
- Summary of Invasiveness
- Taxonomic Tree
- Notes on Taxonomy and Nomenclature
- Plant Type
- Distribution Table
- History of Introduction and Spread
- Risk of Introduction
- Habitat List
- Hosts/Species Affected
- Biology and Ecology
- Air Temperature
- Soil Tolerances
- Notes on Natural Enemies
- Means of Movement and Dispersal
- Pathway Causes
- Pathway Vectors
- Impact Summary
- Economic Impact
- Environmental Impact
- Threatened Species
- Social Impact
- Risk and Impact Factors
- Uses List
- Similarities to Other Species/Conditions
- Prevention and Control
- Gaps in Knowledge/Research Needs
- Links to Websites
- Distribution Maps
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PicturesTop of page
IdentityTop of page
Preferred Scientific Name
- Foeniculum vulgare Miller
Preferred Common Name
Other Scientific Names
- Anethum dulce DC.
- Anethum foeniculum L.
- Anethum minus Gouan
- Anethum panmori Roxb.
- Anethum pannorium Roxb.
- Anethum rupestre Salisb.
- Foeniculum azoricum Mill.
- Foeniculum capillaceum Gilib.
- Foeniculum divaricatum Griseb.
- Foeniculum dulce Mill.
- Foeniculum giganteum Lojac.
- Foeniculum officinale Allioni
- Foeniculum panmorium (Roxb.) DC.
- Foeniculum piperitum C.Presl
- Foeniculum rigidum Brot. ex Steud.
- Ligusticum foeniculum (L.) Roth
- Meum foeniculum (L.) Spreng.
- Selinum foeniculum H.L.Krause
- Seseli foeniculum Koso-Pol.
International Common Names
- English: anise; aniseed; aniseed weed; bitter fennel; common fennel; Florence fennel; Roman fennel; sweet anise; sweet fennel
- Spanish: eneldo; fonol; hinojo; lecherillo
- French: aneth doux; fenouil; fenouil commun; fenuil doux
- Arabic: bisbas; shamar
- Chinese: hui xiang
- Portuguese: funcho
Local Common Names
- Cook Islands: taretare; taretare tui-‘ei
- Cuba: anís de florencia; hinojo común; hinojo de Florencia
- Czech Republic: fenikel oby; fenykl obecný
- Dominican Republic: anís; comino
- Fiji: pan mauri
- French Polynesia: apiti
- Germany: Echter Fenchel; Garten- Fenchel; Gemüsefenchel; Gewürzfenchel; wilder Fenchel
- Guam: anis hinoho
- Haiti: anís vert; L’buit; La nuit
- India: saunf
- Indonesia: adas; adas londo; hades
- Italy: finocchio
- Japan: fenneru; uiky; ui-kyo
- Laos: phak s'i
- Latvia: parast
- Malaysia: adas pedas
- Myanmar: samon-saba
- Netherlands: venkel
- Niue: taletale
- Northern Mariana Islands: anis hinoho
- Philippines: anis; haras
- Puerto Rico: eneldo; esmeldo
- Russian Federation: fenchel' obyknovennyj
- South Africa: vinkel
- Sweden: faenkaal; fänkål
- Thailand: phakchi-duanha; thian-klaep; yira
- FOEVU (Foeniculum vulgare)
Summary of InvasivenessTop of page
Foeniculum vulgare, also known as sweet fennel, is a common kitchen herb used around the world - but it is also a highly invasive weed that can severely damage ecosystems. A risk assessment prepared for Hawaii gave the species a high risk score of 19 (PIER, 2015). F. vulgare is known to alter fire regimes and create dense stands, outcompeting native flora for nutrients and space (DiTomaso et al., 2013; Cal-IPC, 2015). It was listed in the Global Compendium of Weeds as an “agricultural weed, casual alien, cultivation escape, environmental weed, garden thug, naturalised, noxious weed, weed” (Randall, 2012), and is known to be invasive (mostly in natural habitats rather than agricultural land) in California, New Zealand, significant parts of Australia and a number of locations in the Pacific. (PIER, 2015).
The species is a principal weed in Mexico and New Zealand, a common weed in Argentina, Australia, Hawaii, and Spain, weedy in Chile, Morocco, Uruguay, the USA, and Venezuela, and it is known to be adventive in China, Colombia (Holm et al., 1979; Flora of China Editorial Committee, 2015; PIER, 2015; Vascular Plants of Antioquia, 2015). It is also reported as invasive in Ethiopia and Kenya. It can regenerate by both seeds and roots, which often makes physical control methods ineffective and chemical control necessary once a population is established.
Taxonomic TreeTop of page
- Domain: Eukaryota
- Kingdom: Plantae
- Phylum: Spermatophyta
- Subphylum: Angiospermae
- Class: Dicotyledonae
- Order: Apiales
- Family: Apiaceae
- Genus: Foeniculum
- Species: Foeniculum vulgare
Notes on Taxonomy and NomenclatureTop of page
Often called the ‘carrot’ or ‘parsley’ family, the Apiaceae family consists of anise-scented, caulescent annual herbs from taproots characterized by flowers borne in rounded, compound umbels, from which the family’s traditional name of Umbelliferae is derived. The family includes many common vegetables and kitchen herbs such as celery, carrot, fennel, dill, coriander and parsnip. Foeniculum is an Old World genus of several species characterized by anise-scented leaves, stout taproots, and flowers in lax, compound umbels typical of the Apiaceae family (Wagner et al., 2015). The genus name Foeniculum derives from the Latin word ‘foenum’, hay, referring to its strong odour (Britton, 1918).
Mabberley (1997) recognises 4-5 species of Foeniculum from Asia, of which only F. vulgare has become widely naturalized. According to USDA-ARS (2013), two subspecies (F. vulgare subsp. piperitum (Ucria) Cout. – bitter fennel, and F. vulgare subsp. vulgare) are recognised, and the latter subspecies has a number of varieties, including var. azoricum (Mill.) Thell. (Florence fennel or finocchio), var. dulce (Mill.) Batt. (Roman or sweet fennel) and var. vulgare (bitter or common fennel).
Purwaningsih and Brink (1999) describe the three varieties of F. vulgare subsp. vulgare as follows:
- cv. group Bitter Fennel or Common Fennel (other names: F. vulgare Miller var. vulgare; cultivars have fruits with a bitter aftertaste).
- cv. group Florence Fennel (other names: F. azoricum Miller, F. vulgare Miller var. azoricum (Miller) Thellung, finocchio; cultivars with swollen basal part of the petiole which is eaten cooked as a vegetable).
- cv. group Sweet Fennel (other names: F. dolce Miller, F. vulgare Miller var. dulce (Miller) Battand. & Trabut, Roman fennel; cultivars with sweet-tasting fruits).
Other authors use a range of other named varieties, often distinguished on the basis of the composition of their essential oil (Purwaningsih and Brink, 1999).
F. vulgare subsp. vulgare var. azoricum is commercially grown for its swollen leaf bases and edible leaves which can be eaten raw or cooked as a vegetable. The other two varieties are commercially grown for their fruits (‘seeds’) as well as vegetative parts which are used as flavouring, for essential oil production or for their medicinal properties. A reddish-leaved form called bronze fennel is often grown in gardens, and is known as F. vulgare ‘Purpureum’ or F. vulgare var. rubrum.
The invasive or weedy species is referred to as F. vulgare. DiTomaso et al. (2013) say that unlike the weedy form, cultivated varieties are seldom invasive. Possibly the cultivated varieties and forms of this species have become genetically altered over their many centuries of domestication and have lost at least some of their ‘weedy’ characteristics.
DescriptionTop of page
Robust, perennial, glabrous, glaucous, aromatic herb, up to 2 m tall. Stem erect, terete, longitudinally striate, profusely branched at all heights, internodes hollow when older. Leaves alternate, decompound, sheathed, lower leaves largest; leaf sheath forming an open cylinder, at base embracing the stem, 2-15 cm long, margins white scarious, sheath much larger and fleshier in Florence fennel; rest of petiole subterete, 0-10 cm longer than the sheathing part, longitudinally striate; blade triangular in outline, up to 30 cm x 50 cm, 2-6-pinnately divided into filiform, acute, blue-green lobes 1-14 cm long; primary pinnae odd-numbered 3-19. Inflorescence a terminal, compound umbel, up to 20 cm in diameter but usually smaller; peduncle (1-)5-16(-24) cm long; primary rays 5-30(-70) per umbel, 0.5-12 cm long, unequal in length, the shortest ones in the centre; secondary rays (pedicels) (2-)10-30(-45) per umbellet, up to 1 cm long, unequal in length; involucre and involucels absent; calyx vestigial at the top of the ovary; petals 5, distinct, subovate in outline, up to 1.5 mm x 1 mm, with strongly inflexed, notched apex, yellow, with a thin membranous outgrowth on the ventral side of the midrib; stamens 5, about 1.5 mm long; pistil with inferior, bilocular ovary, 2 styles, each with a stylopodium at base and a stigma at top. Fruit an ovoid-cylindrical, usually slightly curved schizocarp, 3-8.5 mm x 2-2.5 mm, light green to yellow-brown, splitting at maturity into 2 mericarps each with 5 prominent ridges and oil-vittae between the ridges. Seed with testa adnate to the pericarp. Seedling with epigeal germination (Purwaningsih and Brink, 1999).
Plant TypeTop of page Broadleaved
DistributionTop of page
F. vulgare is native to the Old World- possibly the Mediterranean region considering its use by the ancient Egyptians, Greeks and Romans- but it has been widely introduced and naturalized around the world and today is reportedly an adventive species in North, Central, and South America and the Caribbean Islands (Liogier and Martorell, 2000; Hanelt et al., 2001; Wyk, 2005; Elzebroek and Wind, 2008).
Fennels cultivated for seed are of two types: sweet fennel and bitter fennel. Sweet fennel is not found wild; it is grown in Bulgaria, France, Italy and Macedonia. Bitter fennel is grown in India, Argentina, Czech Republic, France, Germany, Hungary, Italy, Japan, Romania and Southern Russia. Indian fennel has a sweet anise flavour while the Persian fennel has a strong anise flavour and taste (Ravindran, 2016).
Distribution TableTop of page
The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.
|Continent/Country/Region||Distribution||Last Reported||Origin||First Reported||Invasive||Reference||Notes|
|China||Widespread||Introduced||eFloras, 2013||Cultivated and adventive; 200-2600m. Throughout China|
|-Hong Kong||Present||Introduced||PIER, 2015||Cultivated|
|Georgia (Republic of)||Present||Native||USDA-ARS, 2015|
|India||Present||Hanelt et al., 2001|
|Indonesia||Present||Present based on regional distribution.|
|-Java||Present||Introduced||Purwaningsih and Brink, 1999|
|Myanmar||Present||Kress et al., 2003||Shan|
|Philippines||Present only in captivity/cultivation||Introduced||Merrill, 1923; Quisumbing, 1951||‘Planted here and there about houses but nowhere spontaneous’|
|South East Asia||Present only in captivity/cultivation||Introduced||Purwaningsih and Brink, 1999|
|Cape Verde||Present||Introduced||USDA-ARS, 2013|
|Ethiopia||Present||Introduced||Invasive||Witt and Luke, 2017|
|Kenya||Present||Introduced||Invasive||Witt and Luke, 2017|
|South Africa||Present||Introduced||USDA-ARS, 2013|
|-Canary Islands||Present||Native||USDA-ARS, 2013|
|Bermuda||Present||Introduced||Britton, 1918||Widely distributed as a weed’|
|Canada||Present||Present based on regional distribution.|
|-British Columbia||Present||Introduced||USDA-NRCS, 2013|
|Mexico||Present||Introduced||USDA-ARS, 2013; Flora Mesoamericana, 2015|
|-California||Present||Introduced||Invasive||CAL-IPC, 2005; USDA-NRCS, 2013|
|-Hawaii||Present||Introduced||Invasive||PIER, 2013; USDA-NRCS, 2013; Wagner et al., 2015|
|-Missouri||Present||Introduced||Flora of Missouri, 2015|
|-New Jersey||Present||Introduced||USDA-NRCS, 2013|
|-New Mexico||Present||Introduced||USDA-NRCS, 2013|
|-New York||Present||Introduced||USDA-NRCS, 2013|
|-North Carolina||Present||Introduced||USDA-NRCS, 2013|
|-Rhode Island||Present||Introduced||USDA-NRCS, 2013|
|-South Carolina||Present||Introduced||USDA-NRCS, 2013|
|-West Virginia||Present||Introduced||USDA-NRCS, 2013|
Central America and Caribbean
|Bahamas||Present||Introduced||Acevedo-Rodríguez and Strong, 2012|
|Barbados||Present||Introduced||Acevedo-Rodríguez and Strong, 2012|
|Costa Rica||Present||Introduced||USDA-ARS, 2013; Flora Mesoamericana, 2015|
|Cuba||Present||Introduced||Invasive||Oviedo Prieto et al., 2012|
|Dominican Republic||Present||Introduced||Acevedo-Rodríguez and Strong, 2012|
|El Salvador||Present||Introduced||USDA-ARS, 2013|
|Guadeloupe||Present||Introduced||Acevedo-Rodríguez and Strong, 2012|
|Jamaica||Present||Introduced||Acevedo-Rodríguez and Strong, 2012|
|Martinique||Present||Introduced||Acevedo-Rodríguez and Strong, 2012|
|Netherlands Antilles||Present||Introduced||Acevedo-Rodríguez and Strong, 2012|
|Nicaragua||Present||Flora Mesoamericana, 2015||Widely cultivated and adventive|
|Puerto Rico||Present||Introduced||Liogier and Martorell, 2000; USDA-NRCS, 2013|
|Saint Vincent and the Grenadines||Present||Introduced||Acevedo-Rodríguez and Strong, 2012|
|United States Virgin Islands||Present||Introduced||USDA-NRCS, 2013|
|Bolivia||Present||Bolivia Checklist, 2015; Madidi Checklist, 2015||Cultivated. Cochabamba, La Paz, Santa Cruz|
|-Parana||Present||Introduced||Forzza et al., 2010||Subspontaneous, not endemic|
|-Rio Grande do Sul||Present||Introduced||Forzza et al., 2010||Subspontaneous, not endemic|
|-Santa Catarina||Present||Introduced||Forzza et al., 2010||Subspontaneous, not endemic|
|Chile||Present||Introduced||Invasive||PIER, 2013; USDA-ARS, 2013|
|Colombia||Present||Vascular Plants of Antioquia, 2015||Armenia, Guarne, Medellín, Rionegro|
|Ecuador||Present||Vascular Plants of Ecuador, 2015||Azuay, Bolívar, Loja, Pichincha, Tungurahua|
|-Galapagos Islands||Present||PIER, 2015||San Cristóbal Island. Cultivated|
|Peru||Present||Introduced||Peru Checklist, 2015||Andean I, Andean II, Coastal regions. Dptos Apurí, Arequipa, Cuzco, Lima, San Martín|
|Austria||Present||Introduced||DAISIE, 2015||Alien, not established|
|Belgium||Present||Introduced||DAISIE, 2015||Alien, established|
|Bulgaria||Present||Native||USDA-ARS, 2013; DAISIE, 2015|
|Czech Republic||Present||Introduced||DAISIE, 2015||Alien, not established|
|Germany||Present||Introduced||DAISIE, 2015||Alien, not established|
|Ireland||Present||Introduced||DAISIE, 2015||Cryptogenic, established|
|Liechtenstein||Present||Introduced||DAISIE, 2015||Alien, established|
|Sweden||Present||Introduced||DAISIE, 2015||Alien, not established|
|Switzerland||Present||Introduced||DAISIE, 2015||Alien, established|
|-Channel Islands||Present||Introduced||DAISIE, 2015|
|Ukraine||Present||Introduced||DAISIE, 2015; USDA-ARS, 2015|
|Australia||Widespread||Introduced||Invasive||University of Queensland, 2013; USDA-ARS, 2013|
|-New South Wales||Widespread||Introduced||Invasive||Parsons and Cuthbertson, 1992; University of Queensland, 2013|
|-Queensland||Localised||Introduced||Invasive||Parsons and Cuthbertson, 1992; University of Queensland, 2013||South-eastern areas|
|-South Australia||Widespread||Introduced||Invasive||Parsons and Cuthbertson, 1992; University of Queensland, 2013|
|-Tasmania||Present||Introduced||Parsons and Cuthbertson, 1992; University of Queensland, 2013|
|-Victoria||Widespread||Introduced||Invasive||Parsons and Cuthbertson, 1992; University of Queensland, 2013|
|-Western Australia||Present||Introduced||Parsons and Cuthbertson, 1992; University of Queensland, 2013|
|Cook Islands||Present||Introduced||PIER, 2013|
|Fiji||Present||Introduced||Invasive||PIER, 2013||Cultivated and invasive|
|French Polynesia||Present||Introduced||Invasive||PIER, 2013; Wagner and Lorence, 2015||Cultivated (invasive in Society Islands)|
|Marshall Islands||Present||Introduced||PIER, 2015||Cultivated|
|New Caledonia||Present||Introduced||Invasive||PIER, 2013||Cultivated, invasive|
|New Zealand||Widespread||Introduced||Invasive||Esler, 1988; Webb et al., 1988|
History of Introduction and SpreadTop of page
F. vulgare may be native to the Mediterranean region but it has been cultivated and consumed across Europe for centuries, as it has been well known as a spice and medicinal plant since the time of the ancient Egyptians. It has escaped from cultivation and become an invasive pest in countries with a temperate climate, but is also recorded from tropical localities like Hawaii and Fiji (PIER, 2013).
The species had symbolic significance to the Greeks, particularly in the Battle of Marathon (490 BC); Hippocrates and Dioscorides prescribed fennel as a diuretic and emmenagogue, Romans ate it as a vegetable and chewed its roots as they considered it to curb appetite and control obesity, and Pliny attributed at least twenty medicinal uses to the plant (Quisumbing, 1951; Gerard et al., 1964; Throop, 1998; Wyk, 2005; Balick, 2014). Its medicinal uses were also praised by the 9th century English Benedictine abbot Walahfrid Strabo, the 12th century German mystic Abbess Hildegard von Bingen recommended its use to treat colds, phlegm, eye afflictions, stomach ailments, and insomnia, and by 1636 Gerard wrote in his herbal that the plant was “so well knowne” among the English (Quisumbing, 1951; Gerard et al., 1964; Throop, 1998; Wyk, 2005; Balick, 2014). It was an ingredient in the common drink ‘sack’, mentioned by Shakespeare in The Tempest at the turn of the 18th century, and was an essential ingredient in absinthe, the 19th-century French drink famous for its association with Bohemian artists and writers. Salisbury (1964) comments that the species was probably introduced to Britain from the Continent before 1450. It was introduced to Australia and New Zealand in the 19th century (Parsons and Cuthbertson, 1992; Thomson, 1922).
Date of introduction to the West Indies is uncertain. It was not included in Bello’s work on Puerto Rico (Bello Espinosa, 1881; 1883). In his flora of Bermuda, Britton (1918) reported fennel to have been first introduced to Bermuda as a garden ornamental and that it had since become a widely distributed weed. It was present in the Virgin Islands before 1923, as Britton and Wilson (1923-1926) reported the species as “formerly grown as a drug in the Virgin Islands” in their survey of Puerto Rico and the Virgin Islands.
IntroductionsTop of page
|Introduced to||Introduced from||Year||Reason||Introduced by||Established in wild through||References||Notes|
|Natural reproduction||Continuous restocking|
|Australia||1803||Crop production (pathway cause)||Yes||No||Parsons and Cuthbertson (1992); Parsons and WT, Cuthbertson (1992); ParsonsWT, and Cuthbertson (1992)||New South Wales|
|New Zealand||1864||Yes||No||THOMSON (1922)|
Risk of IntroductionTop of page
The likelihood of introduction to new countries must be high, especially as many people relocate around the world and almost certainly take their crops and spice seeds with them. A PIER risk assessment prepared for Hawaii gave the species a high risk score of 19, where any score greater than 6 would indicate the species’ potential to be high risk and thus should be rejected for import to Australia (PIER, 2015). F. vulgare is a seriously invasive weed known to alter fire regimes and create dense stands, outcompeting native flora for nutrients and space, and thus altering the composition and structure of native communities and reducing species richness (Weber, 2003; DiTomaso et al., 2013; Cal-IPC, 2015).
The species has a rapid growth rate and its seed production is prolific, with tens of thousands of viable seeds per plant in the first season of growth, and hundreds of thousands the following year. Although cultivated varieties are seldom invasive and often grown as an annual crop in temperate areas, F. vulgare is considered an aromatic perennial and grows a deep, thick taproot that is not easily removed (DiTomaso et al., 2013). The species is known to have escaped from cultivation in Puerto Rico and possibly in the Marquesas (Liogier and Martorell, 2000; Randall, 2012; Wagner and Lorence, 2015). It is reportedly adventive in China and Colombia (Flora of China Editorial Committee, 2015; Vascular Plants of Antioquia, 2015). Considering all these factors, F. vulgare is a high-risk species.
HabitatTop of page
F. vulgare grows on a wide range of soil types in humid-temperate regions (Parsons and Cuthbertson, 1992). It grows best in open, unshaded situations and occurs on roadsides, railway easements, channels and drains, rubbish dumps and neglected areas from which it sometimes encroaches onto more productive land. It is restricted to areas of moderate rainfall or where irrigation or run-off water is available, or to low-lying places subject to flooding. It is, apparently, reasonably frost resistant. Purwaningsih and Brink (1999) say that, as a crop, it is grown as a cold-weather crop and does not perform well in the south of India, except at higher elevations.
In California typical habitats invaded by F. vulgare include coastal sage scrub, valley grassland, oak savannah and chaparral (Bell et al., 2008). PIER (2013) describes the species’ habitats in Hawaii, Fiji, Niue and Chile: moisture, exposure to the sun and open sites seem to be common features. It occurs in disturbed areas, loams, and rocky slopes of the Andean and coastal parts of Peru (Peru Checklist, 2015), as well as the Yungas, Dry Valleys, and Dry Puna vegetation zones of Bolivia (Bolivia Checklist, 2015). In Bermuda the species was also reported to grow as a weed in fields, marshes, and waste grounds (Britton, 1918). In Missouri, USA, where the species is introduced, it is found growing around railroads, roadsides, and open, disturbed areas (Flora of Missouri, 2015). In Pakistan the species can be found growing in plains (Flora of Pakistan, 2015).
Habitat ListTop of page
|Terrestrial – Managed||Cultivated / agricultural land||Principal habitat||Harmful (pest or invasive)|
|Cultivated / agricultural land||Principal habitat||Productive/non-natural|
|Disturbed areas||Principal habitat||Harmful (pest or invasive)|
|Disturbed areas||Principal habitat||Natural|
|Rail / roadsides||Principal habitat||Harmful (pest or invasive)|
|Rail / roadsides||Principal habitat||Natural|
|Urban / peri-urban areas||Principal habitat||Harmful (pest or invasive)|
|Urban / peri-urban areas||Principal habitat||Natural|
|Terrestrial ‑ Natural / Semi-natural||Natural forests||Present, no further details|
|Natural grasslands||Present, no further details||Harmful (pest or invasive)|
|Riverbanks||Principal habitat||Harmful (pest or invasive)|
|Wetlands||Present, no further details|
|Scrub / shrublands||Present, no further details||Harmful (pest or invasive)|
Hosts/Species AffectedTop of page
A critically endangered orchid (Diuris fragrantissima) in Victoria, Australia, is threatened by invasive species, including F. vulgare (University of Queensland, 2013).
Biology and EcologyTop of page
2n = 16, 22, 26, 30, 44 (Wagner et al., 2015).
Published material on factors affecting the growth of F. vulgare is abundant, mostly referring to propagation and growth of commercial crops. It is hard to know how much of this information applies to wild populations of 'weedy' F. vulgare.
Erskine-Ogden (2004), cited in CAL-IPC (2005), says that seed production is prolific – tens of thousands of seeds per plant in the first season of growth and hundreds of thousands in the second year. DiTomaso et al. (2013) claim that seeds can apparently survive for several years under field conditions.
Fennel is mainly cross-pollinated, and fruit ripening is uneven according to Purwaningsih and Brink (1999). These authors also report that seed germinates well between 15 and 20°C, with better germination in darkness than in light, and that seed retains its viability for 2-3 years.
Physiology and Phenology
Seeds normally germinate within 2-3 weeks after sowing. Initial development is slow, with a period of 2-2.5 months from sowing to stem emergence. Flowering occurs 3-4 months after sowing, and the time from sowing to first fruit harvest is 5-7 months (Purwaningsih and Brink, 1999).
Peterson et al. (1993) reported that F. vulgare initiated umbels and commenced rapid stem elongation once photoperiods exceeded 13.5 hours. At this stage, plants had developed 15 to 16 nodes below the primary umbel and had 8 to 9 expanded leaves. Fennel requires a minimum of eight fully expanded leaves and at least ten inductive cycles for umbel initiation.
The species grows in all parts of China and has been reported at elevations between 200-2600 m (Flora of China Editorial Committee, 2015). In Colombia it has been reported growing between 1500-2500 m (Vascular Plants of Antioquia, 2015), in Ecuador between 2000-3000 m (Vascular Plants of Ecuador, 2015), and in Bolivia, at elevations up to 4000 m (Bolivia Checklist, 2015). In Pakistan, the species is commonly cultivated from the plains to 2000 m and has a wide distribution (Flora of Pakistan, 2015); it grows at a similar elevation range, 0-2000 m, in Peru (Peru Checklist, 2015).
Fennel thrives best in sunny locations in mild climates; it is primarily a cool-season crop. It prefers well-drained moist loams or loamy clay soils with pH between 6.3 and 8.3. Moisture stress should be avoided (Elzebroek and Wind, 2008). It is restricted to areas of moderate rainfall or where irrigation or run-off water is available, or to low-lying places subject to flooding. It is reasonably frost resistant (Parsons and Cuthbertson, 1992). It is grown as a cold-weather crop and does not perform well, for example, in the south of India, except at higher elevations. The tops are injured by long cold spells, so in temperate regions it is grown as an annual. Fennel is found under conditions of 500-2000(-4000) mm mean annual rainfall and 6-12(-24)°C mean annual temperature. Moisture stress causes the basal stalk to split. Fennel thrives in non-acid, well-drained loams and tolerates a soil pH between 6.3 and 8.3. It is salt-sensitive (Purwaningsih and Brink, 1999). PIER (2013) describes the species’ habitats in Hawaii, Fiji, Niue and Chile; moisture, exposure to the sun and open sites seem to be common features.
(Section from Purwaningsih and Brink, 1999)
Sweet fennel fruits smell strongly of anise and have a penetrating and sweet taste, whereas those of bitter or common fennel have a pungent odour and taste like camphor. Fennel 'seed' contains per 100 g edible portion: water 8.8 g, protein 15.8 g, fat 14.9 g, carbohydrates 36.6 g, fibre 15.7 g, ash 8.2 g (Ca 1.2 g, Fe 19 mg, Mg 385 mg, P 487 mg, K 1.7 g, Na 88 mg, Zn 4 mg), vitamin A 135 IU, niacin 6 mg, thiamine 0.41 mg and riboflavin 0.35 mg. The energy value is about 1440 kJ/100 g. The lipid fraction contains 9.9 g total monounsaturated and 1.7 g total polyunsaturated fatty acids. The fixed oil is mainly composed of petroselinic acid (60-75%), oleic acid and linoleic acid. The fruits also contain flavonoids and stigmasterol. The 1000-seed weight is 4-8 g.
The essential oil is present in secretory channels in most parts of the plant, but in mature fennel about 95% of the oil is located in the fruit. The essential oil yield after hydrodistillation of the fruits is 1.9-3.1%. The oil obtained from sweet fennel possesses a finer odour and flavour than that from bitter fennel. The major compound of sweet fennel oil is (E)-anethole (up to 70-80%), which is responsible for the anise fragrance and sweet taste. The (E)-anethole content of sweet fennel oil is only half that of sweet fennel, whereas the fenchone content is higher. Fenchone is considered a character-impact constituent of sweet fennel oil.
The concentration of major compounds of the essential oil varies with plant part and development stage. In bitter fennel populations from different origins it was found that the anethole and fenchone concentrations were higher in the waxy and ripe fruits than in the stems and leaves, whereas the α-pinene concentration showed an opposite trend. Furthermore, the anethole and fenchone concentrations increased from the bud stage until fruit ripening, whereas the α-pinene and limonene concentrations decreased. The estragole concentration varied only slightly. The composition of essential oil from the roots is very different from that from the rest of the plant, with terpinolene, myristicin and apiole being the main compounds. The residue after essential oil distillation from fennel fruits contains 14-22 % protein and 12-18.5% fat.
Seeds germinate at almost any time of the year but plants do not flower until they are 18 months to 2 years old. Flowering stems grow afresh each spring from the perennial crowns of established plants. In Australia, flowering begins in November and continues through the summer. Seeds are produced in summer and autumn, and the flowering stems brown off and partly die back in winter. In late winter or spring new leaves form on the lower stems and the crown (Parsons and Cuthbertson, 1992).
ClimateTop of page
|Cf - Warm temperate climate, wet all year||Tolerated||Warm average temp. > 10°C, Cold average temp. > 0°C, wet all year|
|Cs - Warm temperate climate with dry summer||Preferred||Warm average temp. > 10°C, Cold average temp. > 0°C, dry summers|
|Af - Tropical rainforest climate||Tolerated||> 60mm precipitation per month|
|BS - Steppe climate||Tolerated||> 430mm and < 860mm annual precipitation|
|Ds - Continental climate with dry summer||Tolerated||Continental climate with dry summer (Warm average temp. > 10°C, coldest month < 0°C, dry summers)|
Air TemperatureTop of page
|Parameter||Lower limit||Upper limit|
|Mean annual temperature (ºC)||6||24|
RainfallTop of page
|Parameter||Lower limit||Upper limit||Description|
|Mean annual rainfall||500||4000||mm; lower/upper limits|
Soil TolerancesTop of page
Notes on Natural EnemiesTop of page
Very many natural enemies of cultivated crops of F. vulgare are listed in the literature; they include insects, nematodes, molluscs, fungi, bacteria and parasitic plants. However, there is little information on how many of these affect populations of wild forms of the species, although presumably many of them can.
Means of Movement and DispersalTop of page
Natural Dispersal (Non-Biotic)
It is possible that the seeds are dispersed by water. Seeds of this species are small and prolific, and the species can grow along riverbeds and is known to escape into coastal areas (Webb et al., 1988; Cal-IPC, 2015; Peru Checklist, 2015).
Vector Transmission (Biotic)
In Australia, and probably elsewhere, the seeds of F. vulgare contaminate agricultural produce, vehicles, machinery, wool and skin of animals, clothing, gravel, mud and water (Parsons and Cuthbertson, 1992). Presumably when livestock (especially thick-fleeced sheep) push through thickets of fruiting plants some of the seeds are dislodged from the plants and fall onto and become entangled in their fleeces. The seeds are eaten by rodents and birds, while feral pigs eat its roots (DiTomaso et al., 2013; Cal-IPC, 2015). In the Channel Islands National Park off the coast of California F. vulgare was apparently introduced in the 1800’s and has become a problematic weed after its seed was spread by animals (US National Park Service, 2015).
Although agricultural and horticultural seeds may be contaminated with those of F. vulgare, in commercial consignments this should be noticed by phytosanitary inspectors following the appropriate regulations. There is however some danger of accidental introduction of seeds (or pieces of crown or root -- Parsons and Cuthbertson, 1992) to new places on agricultural or other machinery, or in mud, gravel or agricultural produce.
Migrants to new countries always take with them something to remind them of their old homes and a few seeds of a favourite flavouring plant would seem sensible. Intentional introduction is almost certainly how F. vulgare has become established in many countries already and its spread to yet more countries where conditions are favourable for its growth is to be expected.
There is considerable international trade in fennel seeds (Purwaningsih and Brink, 1999).
Pathway CausesTop of page
Pathway VectorsTop of page
Impact SummaryTop of page
|Economic/livelihood||Positive and negative|
Economic ImpactTop of page
F. vulgare rarely invades established pastures or regularly cultivated land (Parsons and Cuthbertson, 1992). Although livestock are probably reluctant to eat well developed plants because of the taste, small plants are probably eaten and destroyed by grazing or treading or both. In addition a well-maintained pasture tends to resist invasion by new seedlings.
According to Parsons and Cuthbertson (1992) toxicity problems with grazing animals are not encountered, but deaths of both sheep and cattle have occurred in Tasmania when trash left after distillation of commercially grown fennel was fed to animals (Connor, 1977).
The costs of controlling F. vulgare where it grows in and around railway yards, on roadsides, in industrial areas and in yards where machinery is stored must be considerable whether this is done by machine or by herbicide application.
Environmental ImpactTop of page
Once firmly established, F. vulgare excludes all other vegetation, and apparently tomatoes and beans do not grow in its company, suggesting an allelopathic effect (Parsons and Cuthbertson, 1992).
In California, F. vulgare is classified as one of the most invasive wildland pest plants and is documented as an aggressive invader that displaces natives and disrupts natural habitats (CAL-IPC, 2005). The same source points out that once established it excludes almost all other vegetation, and that soil disturbance encourages it. Furthermore it can alter fire regimes when dry because, once ignited, it creates an intense, fast-moving fire. In California it mainly invades gaps in coastal scrub, where besides causing a fire hazard it shades the understorey herbaceous layer.
The University of Queensland (2013) describes F. vulgare as ‘a significant and widespread environmental weed’, especially in south-eastern Australia (Tasmania, Australian Capital Territory, South Australia, New South Wales), but also in Western Australia and the cooler districts of south-eastern Queensland. It is probably of most concern in Victoria. It is able to outcompete small native understorey shrubs and groundcover plants and is likely to reduce the amount of useful habitat available to native animals. It is especially important along waterways and wetlands but can also affect remnant vegetation in farming areas. It has invaded many conservation areas in south-eastern Australia and probably threatens the last remaining population of the critically endangered sunshine diuris (Diuris fragrantissima).
In New Zealand F. vulgare was reported by Esler (1988) as growing abundantly on roadsides, railway margins, industrial sites and other waste land. He adds that if left unchecked it becomes dominant, and says that part of its competitive success comes from the vigorous rosette on a perennial rootstock, and the shading of other plants from the previous year’s growth, which also creates a fire hazard. It has been considered a problem in New Zealand for over a century, as it was included in the second and third schedules of the Noxious Weeds Act of 1904 (Thomson, 1922).
If long-residual herbicides like diuron or bromacil are used to control F. vulgare, they can sometimes leach into waterways and cause damage to desirable vegetation downstream (Young, 2012).
Threatened SpeciesTop of page
Social ImpactTop of page
Although the leaves and seeds of F. vulgare are used throughout the world as flavouring and for their medicinal properties, plants can sometimes cause adverse effects in mammals. The US Food and Drug Administration (2008) says that the fennels are ‘generally recognized as safe for their intended use’ but also carries reports of seed consumption causing asthma, oestrogenic activity in mice (Malini et al., 1985), and mutagenic activity; these probably occurred when high levels of seeds or extracts were fed.
F. vulgare is among the species of Apiaceae listed by Connor (1977) as causing dermatitis if people handle or touch the plants and are then exposed to sunlight.
Plants for a Future (2013) also warns ‘Skin contact with the sap or essential oil is said to cause photo-sensitivity and/or dermatitis in some people. Ingestion of the oil can cause vomiting, seizures and pulmonary oedema’, citing Foster and Duke (1990). Quoting Karalliedde and Gawarammana (2008), Plants for a Future (2013) also says ‘Avoid for small children. Avoid if cirrhosis/liver disorders.’
Risk and Impact FactorsTop of page Invasiveness
- Proved invasive outside its native range
- Highly adaptable to different environments
- Pioneering in disturbed areas
- Benefits from human association (i.e. it is a human commensal)
- Long lived
- Fast growing
- Has high reproductive potential
- Has propagules that can remain viable for more than one year
- Damaged ecosystem services
- Ecosystem change/ habitat alteration
- Modification of fire regime
- Monoculture formation
- Reduced native biodiversity
- Threat to/ loss of endangered species
- Threat to/ loss of native species
- Competition - monopolizing resources
- Competition - shading
- Competition - smothering
- Highly likely to be transported internationally accidentally
- Highly likely to be transported internationally deliberately
- Difficult to identify/detect as a commodity contaminant
UsesTop of page
F. vulgare subsp. vulgare var. azoricum is commercially grown for its swollen leaf bases and edible leaves which can be eaten raw or cooked as a vegetable. The other two varieties (dulce and vulgare) are commercially grown for their fruits (‘seeds’) and vegetative parts. A reddish-leaved form called bronze fennel is often grown in gardens mainly as an ornamental, and is known as F. vulgare ‘Purpureum’ or F. vulgare var. rubrum.
Fennel has been grown in parts of Europe for human consumption for thousands of years. The leaf bases are eaten raw or cooked as a vegetable; chopped leaves are used to garnish salads, stews and soups; the roots are cooked as a vegetable; the aromatic fruits (known in the trade as ‘seeds’) are used as culinary spice to flavour bread, stews and many other foods and dishes; and whole leaves are used in preparing meat dishes and enhance the flavour of fish. Ground fennel fruit is often a constituent of curry powder. Several sweet, common or bitter cultivars are grown commercially in many countries for the production of anethol, used as a flavouring in foods, cordials and liqueurs like absinthe (Parsons and Cuthbertson, 1992; Purwaningsih and Brink, 1999).
All plant parts contain essential oil, which is used for flavouring, in detergents, and in cosmetics such as soaps, creams, lotions and luxury perfumes. Sweet fennel oil is extensively applied in food products, including alcoholic and non-alcoholic beverages, desserts, candies, baked goods, meat and meat products, condiments and relishes. The maximum permitted level in food products is about 0.3%. Bitter and sweet fennel oils are applied in perfumery, with maximum permitted levels of 0.4%. Sweet fennel oil is used to a limited extent and mainly in cosmetics. Anethole obtained from sweet fennel is applied as a flavouring agent and in the pharmaceutical and perfume industries, but anethole from cheaper sources is usually available. The fruit residue after essential oil distillation may be fed to cattle. In the USA the regulatory status 'generally recognized as safe' has been accorded to common or bitter fennel (GRAS 2481), sweet fennel (GRAS 2482) and sweet fennel oil (GRAS 2483) (Purwaningsih and Brink, 1999).
The medicinal use of fennel also dates from ancient times. It was mentioned by Hippocrates and Dioscorides as a diuretic and as stimulating blood flow in the pelvic area and uterus, and has been used as a main ingredient in the Arab and Ayurvedic medicinal systems. The fruits are widely known as a stimulant, stomachic, expectorant and carminative, and are officinal in many pharmacopoeias. The roots are traditionally applied as a diuretic and purgative. In Indonesia, the fruit is traditionally used in combination with the bark of Alyxia species to give an agreeable flavour to medicines, but the combination is also believed to be useful in the treatment of sprue (coeliac disease). In India, the leaves are considered diuretic, fruit juice is administered to improve eyesight, and hot infusions of the fruits are applied to increase milk secretion and to stimulate sweating. In Chinese herbal medicine, fennel is used against gastroenteritis, hernia, indigestion and abdominal pain, to resolve phlegm and to stimulate milk production. In modern western medicine, fennel and fennel oil are administered as carminative or flavouring agents in certain laxatives. In Germany, the fruits are used in phytomedicine against dyspeptic disorders, as a gastrointestinal antispasmodic, as an expectorant and in syrups against children's coughs (Purwaningsih and Brink, 1999).
In ancient times fennel was credited with magical properties. Prometheus was thought to have brought the fire of the sun from heaven to humans in a hollowed fennel stem. Pliny declared that fennel enabled the eye to perceive the beauty of nature with clarity (Parsons and Cuthbertson, 1992).
The ground spice and the essential oil have antioxidant properties; the essential oil also has antifungal and antibacterial activity, and antiviral activity against Potato virus X, Tobacco mosaic virus and Tobacco ringspot virus. It also shows spasmolytic effects on smooth muscle of experimental animals. Monographs on the physiological properties of sweet fennel oil and bitter fennel oil have been published by the Research Institute for Fragrance Materials (RIFM) (Purwaningsih and Brink, 1999).
As for individual compounds, anethole is effective against Staphylococcus aureus, Escherichia coli, Candida albicans and Corynebacterium sp., and has stimulant and carminative properties. Furthermore, it is allergenic and weakly insecticidal. Long-term studies have shown that it is not carcinogenic. The oestrogenic activity (e.g., increasing milk secretion and promoting menstruation) of fennel is probably due to polymers of anethole, such as dianethole and photanetholes. Estragole is a hepatic carcinogen in mice. In experiments with rats, limonene limited mammary tumour growth (Purwaningsih and Brink, 1999).
Adulterations and Substitutes
Commercial spice samples are sometimes adulterated with sand, stem tissue, fruit residues left after distillation, immature or mouldy fruits or other umbelliferous fruits. Fennel fruits and those of anise (Pimpinella anisum) are often confused and substituted for each other.
Anethole-rich oil is also obtained from P. anisum and star anise (Illicium verum). The cultivation of fennel as a source of anethole was developed in Europe to reduce the dependence on anethole obtained from star anise in Asian countries. Anethole can also be produced chemically, either by hemisynthesis from estragole (e.g., extracted from pine oil) or by complete synthesis. However, in some countries the use of synthetic anethole for food products is prohibited by law.
Uses ListTop of page
Human food and beverage
- Food additive
- Leaves (for beverage)
- Spices and culinary herbs
- Essential oils
- Source of medicine/pharmaceutical
Similarities to Other Species/ConditionsTop of page
The University of Queensland (2013) lists a number of other species from the same family (Apiaceae) which are sometimes confused with F. vulgare, including Berula erecta, Conium maculatum, Ammi majus, Coriandrum sativum, Daucus carota, and Apium graveolens. Purwaningsih and Brink (1999) also say that this species is often confused with dill (Anethum graveolens); the two species are closely related and easily cross. Fennel and dill can be distinguished by their odour (fennel smells like liquorice, dill smells bitter and slightly pungent) and their ripe fruits (fennel has wingless fruits, dill fruits have a wide wing). Fennel plants without fruits may be recognised by their finely dotted stems, the longer and broader leaf sheaths and the usually shorter secondary rays in the umbel.
Prevention and ControlTop of page
The importation and sale of the species are prohibited in Tasmania (University of Queensland, 2013).
Seedlings and smaller plants can be dug out, but crowns and taproots must be removed to prevent regrowth (PIER, 2013). DiTomaso et al. (2013) say that slashing just before flowering may kill the plants, although repeat slashing of regrowth may be needed.
Because the species spreads its roots quickly and creates dense mats that are difficult to physically remove, chemical control is usually necessary once the species is established. Effective herbicides for control of F. vulgare include glyphosate, triclopyr and 2,4-D ester (Weber, 2003). Long-residual herbicides like diuron or bromacil are also used (Young, 2012). Bell et al. (2008) evaluated the impacts of glyphosate and triclopyr applied alone and in combination in natural habitats in California, and also tested spot spraying versus broadcast treatments. They found that glyphosate and triclopyr alone could give very good (but not complete) control of plants for up to a year after application, and that combinations of the two were also effective except when applied at too low a rate or if some plants in the treated area were not contacted by the herbicide. Broadcast spraying was more economical in terms of herbicide use, and spot spraying missed some plants. Also in California (Santa Cruz Island), Brenton and Klinger (2002) report that spraying in the wet season (February-early March) had most effect in reducing cover of fennel. In this study, trichlopyr was effective in reducing F. vulgare, but it is suggested that other restoration techniques may be necessary to enhance habitat for native species following removal of F. vulgare. Power et al. (2014) report that seeding with native seed is a critical step in vegetation restoration on Santa Cruz Island following F. vulgare control.
Pisanu and Mooney (2008) found triclopyr to be the preferred chemical for F. vulgare control on roadsides of Kangaroo Island, South Australia.
After removal of large numbers of sheep and cattle from Santa Cruz Island off the Californian coast in the mid-1990s, many of the island’s vegetation communities became dominated by F. vulgare (Erskine Ogden and Rejmánek, 2005). Presumably before livestock were removed their grazing kept the plants under control.
Erskine Ogden and Rejmánek (2005) tested the efficacy of different control methods on the control of F. vulgare and the effect of management on the recovery of native species on Santa Cruz Island off the coast of California. Experimental plots were burned and then sprayed from the air with triclopyr plus surfactant. Fennel cover decreased significantly from about 60% average cover to less than 3% cover, but the expected increase in native species cover and richness did not occur. Instead fennel plots were replaced by Mediterranean annual grasses such as Avena spp., Bromus hordeaceus, Lolium multiflorum, Hordeum murinum and Bromus diandrus – species that now dominate many Californian landscapes. Surprisingly, though, fennel cover also declined significantly in untreated plots, from 60% cover to just under 40%, while native species richness increased significantly, possibly as a result of the greater vertical complexity of fennel communities, which increased visits by frugivorous birds and may have therefore increased dispersal of seeds of native species.
Gaps in Knowledge/Research NeedsTop of page
Further research is recommended on improving prevention and control methods, as the species is highly invasive yet will continue to be cultivated for its popularity as a spice plant.
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ContributorsTop of page
17/03/15: Updated by:
Marianne Jennifer Datiles, Department of Botany-Smithsonian NMNH, Washington DC, USA
22/06/13: Updated by:
Ian Popay, consultant, New Zealand, with the support of Landcare Research.
Distribution MapsTop of page
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