Common Name: Sweet Fennel

General Information

Foeniculum vulgare cv group Sweet Fennel is a much-branched, erect, biennial to short-lived perennial plant growing from a taproot; it can grow around 100 - 300cm tall[].
Sweet fennel is a cultivated form of fennel with sweeter, more strongly anise-flavoured seeds. It is grown as a culinary and medicinal herb, and also for its sweeter-tasting seeds and essential oil.

Known Hazards

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[].

Botanical References

Range

A cultivar of Foeniculum vulgare.

Habitat

Not found in the wild.

Properties

Edibility Rating
Medicinal Rating
Other Uses Rating
Habit	Perennial
Height	1.50 m
Pollinators	Insects
Self-fertile	Yes
Cultivation Status	Cultivated

Cultivation Details

Foeniculum vulgare is a plant mainly of mediterranean and warm temperate climates. It is fairly cold-hardy, known to tolerate occasional temperatures falling as low as -25°c so long as conditions are fairly dry, though it does lose its top growth in such conditions. It grows best in regions where the mean annual rainfall is within the range 500 - 2,000mm, tolerating up to 4,000mm, and the mean annual temperature is within the range 6 - 12°c, tolerating up to 24°c[, ].
Succeeds in most soils[] but prefers a sunny dry position[]. The plant thrives in non-acid, well-drained loams and tolerates a soil pH between 6.3 and 8.3[].
The flowers are very attractive to bees, butterflies and hoverflies[, ].
Fennel is a poor companion plant in the garden, it inhibits the growth of nearby plants, especially beans, tomatoes and kohl rabi[, ]. It is itself inhibited by wormwood and coriander[, ].

Edible Uses

Leaves - raw or cooked[]. A delicious aniseed flavour[], the young leaves are best since older ones soon become tough. They are often used as a garnish on raw or cooked dishes or added to salads[]. The leaves are difficult to store dried[].

Leaf stalks and flower heads - raw or cooked[, , , ]. An aniseed flavour[].

The aromatic seeds are used as a flavouring in cakes, bread, stuffings etc[, , , , , ]. The sprouted seeds can be added to salads[]. Sweet-fennel fruits smell strongly of anise, and have a penetrating and sweet taste[].

An essential oil from the seed is used as a food flavouring in similar ways to the whole seed[, , ]. The oil obtained from sweet fennel possesses a finer odour and flavour than that from the wild fennel. The major compound of the oil is (E)-anethole (up to 70 - 80%), which is responsible for the anise fragrance and sweet taste. The essential oil yield after hydrodistillation of the fruits is 1.9 - 3.1%[].

Root - cooked[]. The flavour is somewhat parsnip-like.

The leaves or the seeds can be used to make a herb tea[, ].

Medicinal

Fennel is a commonly used household remedy, being useful in the treatment of a variety of complaints, especially those of the digestive system. The seeds, leaves and roots can be used, but the seeds are most active medicinally and are the part normally used[]. An essential oil is often extracted from the seed for medicinal use, though it should not be given to pregnant women[, ]. The plant is analgesic, anti-inflammatory, antispasmodic, aromatic, carminative, diuretic, emmenagogue, expectorant, galactogogue, hallucinogenic, laxative, stimulant and stomachic[, , , , , , , , ]. Fennel is often added to purgatives in order to allay their tendency to cause gripe, and also to improve the flavour[].
An infusion of the root is used to treat urinary disorders[].
An essential oil obtained from the seed is used in aromatherapy. Its keyword is 'Normalising'[]. The essential oil is bactericidal, carminative and stimulant[]. Some caution is advised, see notes above on toxicity[].
The fatty oil obtained from the seed has antimicrobial properties[].

Other Uses

The seed yields up to 5% of an essential oil[, , ]. This is used medicinally, as a food flavouring, in toothpastes, soaps, perfumery, air fresheners etc[, , ]. The flavour of fennel oil depends upon its two main constituents. 'Fenchone' is a bitter tasting element whilst 'anethole' has a sweet anise-like flavour[]. The proportions of these two ingredients varies according to strain and region. Plants growing in the Mediterranean and southern Europe usually have a sweet oil whilst plants growing in central and northern Europe usually produce a more bitter oil[]. This cultivated variety of fennel is low in fenchone - it contains anethol (50 - 80%), limonene (5%), fenchone (5%), estragol (methyl-chavicol), safrol, alpha-pinene (0.5%), alpha-phellandrine, camphene, beta-pinene, beta-myrcene and p-cymen[]. The quality of the oil also depends upon how well the seed has been dried - the oil from fully ripened and dried seeds being much sweeter and more fragrant[].

The seeds of fennel contain approximately 20% fatty oil, of which about 80% is petroselinic acid[]. This acid is of interest because of its antimicrobial activity and because its oxidation gives Lauric acid (C12:0), a very important fatty acid used in the soap, cosmetic, medical and perfume industries[].

The dried plant is an insect repellent[, ], the crushed leaves are effective for keeping dogs free of fleas[]. The plant was formerly used as a strewing herb[].

Yellow and brown dyes are obtained from the flowers and leaves combined[].

Propagation

Seed - best sown in early spring in situ[].
Division in early spring as the new growth appears[, ].