Fennel (Foeniculum vulgare)

Description

Fennel, is the cultivated form of the species Foeniculum vulgare, belonging to the botanical family Apiaceae. It originated in the Mediterranean basin, where it has grown spontaneously for centuries across warm coastal soils and permeable terrains. Over time, cultivation has spread widely in temperate regions.

The plant may be annual or biennial. It features a taproot, an erect hollow stem, finely divided filiform leaves, and—when allowed to mature—umbel-shaped inflorescences bearing small yellowish flowers followed by dry fruits (commonly referred to as “seeds”). The distinctive edible portion of the cultivated type is the bulb-like structure formed at the base: this is actually a fleshy leaf-sheath cluster known as the “bulb” or grumolo, composed of overlapping, thickened leaf bases rather than a true botanical bulb.

Color ranges from white to pale green and is often enhanced by agronomic practices (such as soil hilling) that limit light exposure, ensuring a bright, tender appearance. The bulb is appreciated for its crisp texture, refreshing juiciness, mild sweetness, and characteristic anise-like aroma, largely originating from volatile essential oils, primarily anethole and fenchone.

Plant height typically varies between 60 and 80 cm under optimal conditions. Soil structure, water availability, temperature, and variety influence the bulb shape, density, aroma, dry matter, sweetness, and nutritional composition. Its gastronomic versatility, digestibility, and cultural diffusion make fennel a recognized and valued component of the Mediterranean diet.

Botanical classification

• Common name: Fennel

• Clade: Angiospermae

• Order: Apiales

• Family: Apiaceae

• Genus: Foeniculum

• Species: Foeniculum vulgare Mill.

Climate
Fennel prefers a temperate climate, with mild autumns and springs that support regular growth and the formation of fleshy, well–packed bulbs. It tolerates moderate cold fairly well, especially in the more advanced stages of development, while it is more sensitive to prolonged high temperatures and drought, which can induce premature bolting and produce less compact bulbs.

Exposure
The ideal exposure is full sun, which allows efficient photosynthesis, vigorous growth and good bulb quality. In very hot areas, especially for summer sowings aimed at autumn harvests, light shading during the hottest hours can help reduce water and heat stress and limit the tendency to bolt.

Soil
Fennel grows best in medium–textured, deep, well–drained soils that are rich in organic matter, with a neutral to slightly subalkaline pH. A soft soil, free from waterlogging and well worked in depth, promotes root development and uniform bulb enlargement. Very compact or poorly aerated soils hinder growth and increase the risk of rot.

Irrigation
Irrigation must be regular and fairly constant, keeping the soil moderately moist without excesses. Periods of drought alternating with heavy watering can cause splitting, fibrous bulbs or an increased tendency to bolt. Water should be applied evenly, preferably in the morning or late afternoon, avoiding excessive wetting of the foliage. Mulching can help reduce evaporation and stabilise soil moisture.

Temperature
The optimal temperature range for germination and growth is usually between 15 and 22 °C. Excessively high temperatures, especially when combined with limited water availability, encourage early flower stem formation at the expense of bulbs. Fennel can tolerate lower temperatures in the later stages, but intense or prolonged frosts may damage the more tender tissues.

Fertilization
Fertilization of fennel is based on a good supply of well–matured organic matter before planting, which improves soil structure and fertility. As a crop that produces a fleshy, voluminous edible part, it requires a balanced availability of nitrogen, phosphorus and potassium. Nitrogen should be applied carefully and, if needed, in split doses, to support growth without causing excessive vegetative development or overly watery tissues; phosphorus and potassium help strengthen bulbs and improve their keeping quality.

Crop care
Crop care includes weed control by light hoeing or mulching, especially in the early growth stages. It is important to keep the soil surface loose to promote aeration and drainage. During bulb enlargement, it is common practice to gently ridge soil around the base of the plants to encourage blanching and protect tissues from direct light, improving appearance and tenderness. Regular monitoring helps to detect pests and diseases at an early stage, allowing appropriate interventions.

Harvest
Fennel is harvested when the bulbs have reached the desired size and firmness, appearing white, firm and free from splitting. The plant is cut at the base, removing the tougher outer leaves and trimming the bulb. It is important not to delay harvest too long, to avoid fibrous bulbs or the onset of bolting, both of which reduce quality.

Propagation
Propagation is by seed, usually by direct sowing in the field or in finely prepared beds. Seeds are sown in rows, and the soil is kept moist until germination. After emergence, thinning is carried out to give each plant enough space to form well–developed bulbs. Alternatively, seedlings can be raised in seedbeds and transplanted once they have produced several true leaves, scheduling sowing according to the desired harvest period.

Indicative nutritional values per 100 g

(Edible portion, raw bulb)

• Energy: ~ 31 kcal

• Water: ~ 90%

• Carbohydrates: ~ 7–8 g

• Dietary fiber: ~ 3 g

• Proteins: ~ 1–1.3 g

• Total fats: ~ 0.2 g

• Vitamins: vitamin C, vitamin K, several B-group vitamins

• Minerals: potassium, calcium, phosphorus, magnesium, trace iron and other oligoelements

Values vary with cultivar, climate, fertilization, irrigation, season, and post-harvest handling.

Key constituents

• Water (major component)

• Dietary fiber

• Minerals: potassium, calcium, phosphorus, magnesium, trace iron

• Vitamins: vitamin C, vitamin K, B-group vitamins

• Volatile essential oils: anethole, fenchone, estragole

• Phenolic and antioxidant substances in variable concentration

Production process

• Soil preparation: loose, fertile, well-drained soil worked in depth

• Sowing or transplanting: seeds or seedlings settled in rows

• Crop management: regular irrigation, weed control, nutrient balance

• Bulb formation: thickening and enlargement of basal leaf sheaths

• Blanching (optional): partial burial of the base to preserve whiteness

• Harvesting: when the bulb reaches full size, shows compact structure, and retains optimal firmness

Physical properties

• compact, dense bulb

• crunchy structure and high juiciness

• pale white-to-light-green color

• fleshy leaf bases forming a rounded false bulb

• finely divided leaves in non-harvested plants

Sensory and technological properties

• delicate aroma with anise/liquorice-like notes

• light sweetness, refreshing profile

• firmness and crispness when raw

• soft, velvety texture when cooked

• good compatibility with heat, flavor absorption, and various cooking styles

Food applications

• raw: in salads, pinzimonio, fresh vegetable platters

• cooked: boiled, braised, roasted, baked au gratin, stir-fried, blended into soups

• foliage: as an aromatic herb in sauces, fish dishes, broths, dressings

• seeds (from wild types): used as spice, aromatic ingredient, liqueur component, bakery flavoring

Nutrition and health

Fennel is considered a light and digestible vegetable, characterized by low energy density and a meaningful supply of dietary fiber, water, vitamins, and minerals. Fiber promotes intestinal regularity, satiety, and overall balance of digestive processes, while the mineral profile—especially potassium—supports water–electrolyte balance.

The presence of vitamin C, phenolic fractions, and volatile constituents contributes to antioxidant support. Traditional uses associate fennel with carminative activity, helping reduce bloating and gas formation and supporting post-meal comfort. Thanks to low caloric load and hydration index, it fits well in weight-management or health-oriented diets.

Portion note

A typical serving corresponds to approximately 100–150 g of raw fennel bulb (one medium bulb).

Allergens and intolerances

Fennel is generally well tolerated.
However, individuals with known sensitivity to botanicals within Apiaceae should exercise caution.

Storage and shelf-life

• whole bulb: refrigerated, usually maintains freshness for 4–7 days

• cut fennel: best consumed within 24–48 hours

• cooked preparations: store refrigerated and consume promptly

• dried seeds: retain aromatic strength for several months if stored airtight and protected from light

Safety and regulatory

Fennel is considered safe for standard food use in its common edible parts: bulb, leaves, and seeds. No special regulatory restrictions apply to the fresh vegetable. Standard hygienic practices—washing, safe sourcing, proper storage—are sufficient.

Concentrated derivatives, such as pure essential oils, should be handled prudently, while normal culinary consumption of the bulb is not associated with safety concerns.

Labeling

Food labeling for packaged fennel may include:

• product name (fennel)

• commercial form (bulb, seed, leaf if applicable)

• net quantity

• country of origin

• storage instructions (when needed)

• packaging or expiry date for pre-packed units

• ingredients list for processed foodstuffs containing fennel

Troubleshooting

Cultivation issues

• poor drainage → irregular bulb formation

• insufficient water → slow growth, small bulbs, early bolting

• weeds → competition for nutrients and moisture

• frost exposure → tissue damage and loss of firmness

Post-harvest issues

• dehydration → loss of crispness

• excessive storage → loss of aroma, reduced quality

Main INCI functions (cosmetics)

Extracts derived from Foeniculum vulgare (often from seeds or aromatic fractions) may be used in cosmetic formulations with:

• fragrance function

• potential toning support

• support to antioxidant protection in specific formulations

Such cosmetic applications are secondary and less prominent than culinary uses.

Conclusion

Fennel, combines botanical interest, culinary breadth, and nutritional value. Appreciated in traditional Mediterranean cooking, it offers a crunchy bulb, mild sweetness, and a uniquely anisate aromatic profile. Its composition—high water content, meaningful dietary fiber, mineral supply, and natural volatile compounds—makes it suitable for regular consumption in balanced diets.

It performs well in both raw and cooked preparations, enhancing dishes with freshness, texture, and a light aromatic signature. Favorable digestibility and traditional digestive support consolidate its place as a functional and health-supportive vegetable. Although its cosmetic use is secondary, aromatic extracts may contribute fragrance and potential toning qualities to certain formulations.

Easy to cultivate, simple to store, and versatile in kitchens, fennel holds a well-established role among the most useful and adaptable vegetables, uniting gastronomy, wellness, and cultural tradition.

Studies

Fennel is one of the highest plant sources of potassium, sodium, phosphorus and calcium (1).

Fatty acids. About twenty-one fatty acids have been identified and quantified by fennel (2).

From the fennel is obtained an essential oil that is used against pathogens (3).

This study explains the antiperglycemic activity of fennel extract in investigations undertaken in laboratory animals (4).

Fennel studies

References______________________________________________________________________

(1) Shamkant B. Badgujar, Vainav V. Patel, and Atmaram H. Bandivdekar Foeniculum vulgare Mill: A Review of Its Botany, Phytochemistry, Pharmacology, Contemporary Application, and Toxicology Biomed Res Int. 2014; 2014: 842674.  doi:  10.1155/2014/842674

Abstract. Foeniculum vulgare Mill commonly called fennel has been used in traditional medicine for a wide range of ailments related to digestive, endocrine, reproductive, and respiratory systems. Additionally, it is also used as a galactagogue agent for lactating mothers. The review aims to gather the fragmented information available in the literature regarding morphology, ethnomedicinal applications, phytochemistry, pharmacology, and toxicology of Foeniculum vulgare. It also compiles available scientific evidence for the ethnobotanical claims and to identify gaps required to be filled by future research. Findings based on their traditional uses and scientific evaluation indicates that Foeniculum vulgare remains to be the most widely used herbal plant. It has been used for more than forty types of disorders. Phytochemical studies have shown the presence of numerous valuable compounds, such as volatile compounds, flavonoids, phenolic compounds, fatty acids, and amino acids. Compiled data indicate their efficacy in several in vitro and in vivo pharmacological properties such as antimicrobial, antiviral, anti-inflammatory, antimutagenic, antinociceptive, antipyretic, antispasmodic, antithrombotic, apoptotic, cardiovascular, chemomodulatory, antitumor, hepatoprotective, hypoglycemic, hypolipidemic, and memory enhancing property. Foeniculum vulgare has emerged as a good source of traditional medicine and it provides a noteworthy basis in pharmaceutical biology for the development/formulation of new drugs and future clinical uses.

(2) Roby MHH, Sarhan MA, Selim KA, Khalel KI. Antioxidant and antimicrobial activities of essential oil and extracts of fennel (Foeniculum vulgare L.) and chamomile (Matricaria chamomilla L.) Industrial Crops and Products. 2013;44:437–445.

(3) Kwiatkowski P, Pruss A, Masiuk H, Mnichowska-Polanowska M, Kaczmarek M, Giedrys-Kalemba S, Dołęgowska B, Zielińska-Bliźniewska H, Olszewski J, Sienkiewicz M. The effect of fennel essential oil and trans-anethole on antibacterial activity of mupirocin against Staphylococcus aureus isolated from asymptomatic carriers.    Postepy Dermatol Alergol. 2019 Jun;36(3):308-314. doi: 10.5114/ada.2018.76425

Abstract. Introduction: Staphylococcus aureus constitutes the most pathogenic species within the staphylococcal genus. Humans remain the major reservoirs of this pathogen which colonizes mostly anterior nares of healthy individuals. Aim: To investigate the effect of fennel essential oil (FEO) and trans-anethole (tA) on antibacterial activity of mupirocin (MUP) against S. aureus strains isolated from asymptomatic carriers. Material and methods: The content of the FEO was analysed with use of the GC-MS method. The research done on 43 S. aureus isolates with different resistance patterns, obtained from nasal vestibule. Antibacterial activity of MUP in combination with FEO or tA was examined using the agar dilution method and E-test method. The data analysis was done with the Pearson's χ2 test. Results: The chemical composition of FEO was consistent with the European Pharmacopoeia (EP) for the main constituent - tA (77.9%) according to the EP recommendations. Macrolide-lincosamide-streptogramin B resistance phenotype was prevalent among 39.5% of S. aureus isolates. FEO concentrations of 2.0% and 2.5% revealed antibacterial activity against 76.7% of isolates, whereas tA inhibited S. aureus growth at concentrations > 4.0%. The MIC values for MUP combined with FEO as well as for MUP combined with tA were < 0.064 µg/ml for 79.1% and 86.0% of S. aureus isolates, respectively. Conclusions: Our experiment revealed FEO and tA influence on MUP effectiveness. The combination of MUP with FEO as well as MUP with tA are worth considering to implement in S. aureus eradication procedures. These findings will be useful in designing efficient antistaphylococcal agents which can limit the emergence of antibiotic resistance.

(4) El-Ouady F, Lahrach N, Ajebli M, El Haidani A, Eddouks M.  Antihyperglycemic effect of the aqueous extract of Foeniculum vulgare in normal and streptozotocin-induced diabetic rats.   Cardiovasc Hematol Disord Drug Targets. 2019 Jun 12. doi: 10.2174/1871525717666190612121516