Fennel

Foeniculum vulgare

Family: Apiaceae Part used: Seeds, fronds, bulb

Key Compounds

• trans-Anethole
• Fenchone
• α-Pinene
• Limonene
• Estragole
• p-Anisaldehyde
• Quercetin

Traditional Use

• Ancient Greek mythology — Prometheus transported fire from the gods hidden in a fennel stalk
• Ancient Roman cooking and medicine — Pliny documented 22 remedies; gladiators reportedly ate it for strength
• Medieval Catholic fast days — seeds chewed to suppress hunger during fasting
• Italian cuisine — fennel seeds in finocchiona sausage; bulb in salads and braises; pasta con le sarde
• Traditional Japanese and Chinese medicine — 茴香 (uikyō) seeds used as a spice and digestive

The Battle of Marathon was fought on a field of fennel.

The ancient Greek word for fennel is marathon (μάραθον). The plain of Marathon, where a Greek force stopped the Persian invasion in 490 BCE, was named for the fennel growing there. The modern marathon race — 26.2 miles, run in every city in the world — commemorates the legendary run from that battlefield to Athens. Every marathon runner is, at one remove, competing in a race named after a plant that still grows in Greek scrubland.

Fennel had another role in Greek mythology. Prometheus, who stole fire from the gods to give to humans, transported the burning coal hidden inside a fennel stalk. The hollow stems of giant fennel (Ferula communis) can carry a slow ember without the outside burning — a practical property that made the myth physically possible. The fennel did not apply for the job. It was just hollow.

Meet the plant

A tall, feathery perennial — 1 to 2.5 metres — with leaves finely divided into hair-like fronds that look like dill and smell unmistakably of anise. Hollow blue-green stems. In summer, large flat-topped clusters of small yellow flowers. Seeds that are small, ridged, oval, grey-green, and intensely aromatic.

What makes fennel unusual is that it is three completely different culinary things from one species. Fennel seeds — dried fruit, globally the most common form. Fennel herb — the feathery green fronds used fresh, particularly with fish. Florence fennel — a cultivated variety grown for its swollen bulb-like stem base, an Italian vegetable. All from Foeniculum vulgare. All with the same anise character. All used differently. Most people in Japan know, at most, one of these.

From Prometheus to the pasta bowl

The Romans spread fennel through their empire. Pliny listed 22 remedies. Gladiators reportedly ate it. Medieval Catholic fast days used the seeds as hunger suppressants — they were chewed between meals. The post-meal digestive bowl at an Indian restaurant is the same idea, two thousand years later, with better seating.

Italy is where fennel became cuisine rather than medicine. Florence gave its name to the bulbing variety, finocchio. Tuscany produced finocchiona — a sausage defined entirely by fennel seeds. Sicily has pasta con le sarde, built around fennel fronds and sardines. Provence puts fennel branches on the fire when grilling fish. Italy uses all three forms of the plant, in different regions, for different purposes, without confusion.

The traditional East Asian use is entirely separate and considerably older in Japan. 茴香 (uikyō) appears in Chinese medicine, in Chinese five-spice powder, and in Kampo formulas. The seeds have been used as a digestive spice in Japanese traditional medicine for centuries. Most Japanese people who know 茴香 as a Kampo ingredient do not connect it to the feathery Western herb sold in supermarkets as フェンネル. The bridge between them is chemistry, not naming.

The chemistry

Fennel, anise, and star anise all taste like anise. This is because they all produce the same compound: trans-anethole.

Here is what makes this worth noticing. Fennel and anise are both in the carrot family (Apiaceae). Star anise is in Schisandraceae — an entirely different botanical order from Asia. Three completely unrelated evolutionary lineages, on different continents, arrived at the same chemical solution for what they should smell like. This is convergent evolution, and it is one of the better examples in plant chemistry. When you smell “anise” in any of them, you are smelling the same molecule every time. They did not coordinate. They just arrived.

Fenchone is the secondary compound — bitter, slightly camphor-like, more prominent in wild and bitter fennel varieties. The ratio of anethole to fenchone is what makes a fennel variety “sweet” or “bitter.” Sweet fennel has less of it. That ratio is the whole story.

What people actually do with it

The seeds are the oldest and most globally spread form. Dry-toast them in a pan before grinding — the aromatic oils wake up completely differently with heat, and the difference is not subtle. They go into Indian spice blends (panch phoron), Chinese five-spice, Italian finocchiona sausage, European rye bread and biscotti. The digestive bowl at an Indian restaurant contains fennel seeds for the same reason Roman physicians documented fennel as a digestive. Two thousand years of consistent use is the oldest form of evidence.

The fresh fronds are fennel’s most distinctive use in European cooking. The classic pairing is with fish — the anise cuts through fat in a way that feels purposeful. Pasta con le sarde, the Sicilian dish of pasta with sardines, fresh fennel fronds, pine nuts, saffron, and raisins, is one of those dishes where every single ingredient is doing a specific job and removing any of them is immediately obvious.

Florence fennel (the bulb) is the mildest form and the most likely to surprise people who only know fennel as a seed. Sliced thin with orange and parmesan, braised in white wine, roasted until caramelised — the anise flavour is present but quiet.

The anise spirits — pastis, ouzo, sambuca — are all anethole. Different plants, same compound, same milky-white colour the moment you add water. The plant found the molecule; humans found many different ways to dissolve it in alcohol.

Could you grow this yourself?

Fennel grows easily in most of Japan — tall, self-seeding, drought-tolerant once established. Plant in spring in full sun; it does not need rich soil.

One important constraint: fennel is allelopathic. It releases compounds that inhibit the growth of many neighbouring plants — particularly tomatoes, peppers, and beans. Keep it separated from vegetables. Give it its own corner. The plant has preferences about its neighbours. They are not negotiable.

Florence fennel is grown as an annual, planted in spring, harvested before it bolts. The bulb forms best in cooler late-spring conditions. Mound soil around the forming bulb to produce a larger, milder result.

Fennel (フェンネル/ウイキョウ) in Japan

Two separate identities, rarely connected.

The older: 茴香 (uikyō) — fennel seeds as a spice and medicinal material in Japanese and Chinese traditional medicine. Ancient use, seeds in traditional formulas, available from Chinese medicine ingredient shops. This is a Kampo ingredient.

The newer: Italian. Florence fennel (フィノッキオ) and fresh fennel fronds arrived through Japanese engagement with Italian cuisine. High-end supermarkets (Kinokuniya, Seijo Ishii, Isetan food hall) and Italian restaurants carry the bulb. Japanese home cooks interested in Italian cooking encounter the fronds through cookbooks and cooking media.

茴香 and フェンネル are the same plant. Most Japanese people know one or the other, not both. This is not a problem the plant is aware of.

Things you’re probably wondering

Is ‘marathon’ really named after fennel? Yes. The Greek word for fennel is ‘marathon’ (μάραθον). The Battle of Marathon in 490 BCE was fought on a plain covered with fennel — the site was named for what grew there. The modern marathon race is named after that battle. Every marathon runner is, at one remove, running a race named after a plant.

Why do fennel, anise, and star anise taste the same? Because they all produce the same compound: trans-anethole. This is convergent chemistry — three completely unrelated plants (fennel and anise are both Apiaceae, star anise is Schisandraceae from a different order entirely) independently evolved to produce anethole as their dominant volatile aromatic compound. When three separate lineages arrive at the same chemical solution, you get three plants that taste the same despite no botanical relationship. This is why ‘anise-flavoured’ describes a chemical, not a botanical family.

What is the difference between fennel seeds, fennel herb, and Florence fennel? All three come from the same plant species (Foeniculum vulgare) but different varieties and parts. Fennel seeds are the dried fruit — the most globally widespread form, used in Indian, Chinese, Italian, and Middle Eastern cooking. Fennel herb refers to the feathery green fronds — used fresh like an herb, particularly with fish. Florence fennel (finocchio) is a cultivated variety grown specifically for its swollen bulb-like stem base — an Italian vegetable, eaten raw or braised. The seeds are the strongest in flavour; the bulb is the mildest.

Is fennel the same as anise? No — different plants, but similar flavour because both are dominated by anethole. Anise (Pimpinella anisum) is a different Apiaceae plant, grown primarily for its seeds. The confusion is long-standing — ‘anise-flavoured’ is often used for fennel, and in some languages ‘anise’ and ‘fennel’ are nearly synonymous in colloquial use. In Japanese, 茴香 (uikyō) can refer to both, depending on context.

Where can I find fennel in Japan? Fennel seeds are in every Japanese spice section. Fresh fennel fronds appear occasionally in larger supermarket herb sections (availability is inconsistent). Florence fennel bulb is at high-end supermarkets (Kinokuniya, Seijo Ishii, Isetan food hall) and Italian food specialist stores. 茴香 seeds for medicinal use are available from Chinese medicine ingredient shops. Fennel plants are sometimes sold at garden centres.

Botanical details

The full compound list

See Also

• Dill — same family (Apiaceae); similar feathery appearance, often confused with fennel fronds; flavour is different (dill has no anethole)
• Ginger — another seed-spice with long Japanese traditional use that has also gained a fresh-herb identity
• Thyme — Lamiaceae; Mediterranean origin; classic cooking companion

References

• Patra, J.K. & Baek, K.H. (2016). Antibacterial activity and action mechanism of the essential oil from Fagara zanthoxyloides. Plants, 5(2), 22.
• Badgujar, S.B. et al. (2014). Foeniculum vulgare Mill: A review of its botany, phytochemistry, pharmacology, contemporary application, and toxicology. BioMed Research International, 2014.
• European Medicines Agency (2007). Assessment report on Foeniculum vulgare Miller. EMA/HMPC/137246/2006.
• Piccaglia, R. & Marotti, M. (2001). Characterization of several aromatic plants grown in northern Italy. Flavour and Fragrance Journal, 16(4), 275–285.