Bronze Fennel: The Purple-Leaved Herb Fennel and How to Cook With It

Bronze fennel is common fennel in a purple-bronze coat. It’s grown mostly as an ornamental, but you can eat it from flower to seed. It tastes of anise like any fennel, but don’t go looking for a bulb: it doesn’t make the swollen white one sold as Florence fennel. Cooks use the feathery fronds, the seeds, and the pollen and flowers instead. If you grow it somewhere mild, though, cut the flower heads before the seed drops.

At a glance

What bronze fennel is

Every culinary fennel is the same species, Foeniculum vulgare, a perennial herb in the Apiaceae. Kew’s Plants of the World Online doesn’t recognize any subspecies or varieties within it.³ Bronze fennel is a garden cultivar of that species. Chef and forager Alan Bergo gives its name as Foeniculum vulgare purpureum and describes it as an herbaceous perennial, a cultivar of bulb fennel usually grown as an ornamental. University of Illinois Extension lists a bronze-leaved ornamental type alongside herb fennel and Florence fennel.

Bronze fennel and bulb fennel

The swollen “bulb” at the grocery store is the stem base of Florence fennel, variety azoricum.⁴ Bronze fennel doesn’t make one. The University of Washington’s Miller Library says it plainly: common or bronze fennel, 3 to 5 feet tall with a tough stalk, doesn’t form bulbs.¹ Bergo agrees.

So you can’t use bronze fennel in a recipe that needs the bulb’s crisp, juicy flesh. Its fronds can stand in for bulb fennel fronds, though, and its seeds for fennel seed.

Flavor and the compounds behind it

Herb fennel and Florence fennel both taste of anise or licorice. Bergo finds the anise strongest in the young purple fronds. Once the plant flowers and turns green, the fronds taste more vegetal.

The chemistry is fennel’s in general. Britannica and PROSEA name anethole as the main component of sweet fennel oil, behind its anise smell and sweet taste.⁴ PROSEA says about 95% of the oil in mature fennel sits in the fruit, the “seed”.² We found no analysis of the bronze cultivar itself, so whether its oil differs from green fennel’s hasn’t been measured.

For the seed in detail, see fennel seed.

Origin and history

Fennel is native from the Mediterranean to Ethiopia and western Nepal. None of our sources say where the bronze cultivar itself came from.

• Hippocrates. Hippocrates and Dioscorides both mentioned fennel as a diuretic and emmenagogue.
• Marathon. The Greek word for fennel was marathon, and the town of Marathon was probably named “fennel field” because the plant grew there.⁵ The story that Pheidippides carried a fennel stalk on his run to Athens has no source we could find.
• California. Fennel is an introduced plant in California. Saveur, writing in 2000, said fennel grows all over California and that Italian immigrants brought it in the 1800s.⁶ We found no source for the claim that Spanish explorers brought it in the 17th century.

You may also read that fennel use goes back to ancient Egypt, that Pliny listed it for 22 conditions, that people nibbled the seeds on medieval fast days, and that Culpeper recommended it as an antidote to poison. We couldn’t trace any of those to a source we could open.

A weed in warm places

Bergo calls bronze fennel a heavy self-seeder that’s invasive in warmer climates, though not a problem where winters are cold, as in Minnesota. Common fennel is listed as a non-regulated noxious weed in King County, Washington,¹ and the California Invasive Plant Council rates Foeniculum vulgare a moderate invasive, with dense populations on Santa Cruz Island, around the San Francisco Bay and at Camp Pendleton. Cal-IPC notes it’s still unclear whether the culinary varieties are invasive.⁷ If you garden somewhere mild, cut the flower heads before the seed drops.

How bronze fennel is used

• Fronds. Use them in salads and as a garnish. Herb fennel also goes into fish dishes, soups and stews, and you can cut the foliage as needed or air-dry it.
• Seeds. Fennel seed is a sausage spice, and Bergo uses bronze fennel seed in Italian fennel sausage and in rubs and seasonings for fish. Fennel seed is also one of the five spices in Chinese five-spice powder.
• Pollen and flowers. The flowers and pollen are edible too. See fennel pollen.
• Whole fish. Stuff fronds and stalks into the cavity of a fish before roasting.

For more ideas, see bronze fennel uses and fennel pollen uses.

Buying and storage

Bronze fennel is usually grown as an ornamental, so your easiest source is often a garden. You can air-dry fennel foliage and store it for later. We didn’t find a published storage time for fresh fronds. Treat them like other tender herbs and use them within a few days.

Safety

Fennel contains estragole. In 2001 the EU’s Scientific Committee on Food concluded that estragole has been shown to be genotoxic and carcinogenic.⁸ In 2022 Germany’s BfR said fennel tea, basil pesto and some plant-based supplements may contain high amounts of such compounds, while the health risk couldn’t yet be conclusively assessed.⁹ We found no estragole measurement for bronze fennel fronds and no regulatory limit for fennel as an herb.

You’ll see fennel credited with anti-inflammatory effects or lower disease risk, but no regulator summary we found supports those claims, and we’re not claiming bronze fennel treats or prevents anything. There’s no nutrient data for bronze fennel specifically.

Substitutes and comparisons

For fronds, the leafy tops of bulb fennel or a little dill come closest. For seed, plain fennel seed is the same thing.

• Fennel vs. dill
• Fennel seed substitutes
• Fennel seed vs. anise seed
• Fennel pollen vs. fennel seed