Plant Story--Fennel, Foeniculum vulgare, the Original Marathon

Fennel, Foeniculum vulgare, was called márathon in Greek. 

In the late summer of 490 BCE, a small army from the Greek City-State of Athens defeated a much larger Persian army on the plain of Marathon. This plain had abundant wild fennel, which is why it was called Marathon. Then a messenger from the Greek army ran 26.2 miles without stopping, to bring the news of the victory to Athens. The battle was a major event in the wars between Greece and Persia and commoration by running the distance from Marathon to Athens became a common celebration, called a marathon. You doubtless know that story, but not that marathon means fennel. (Many of the details are unclear see for example link).

Fennel, Foeniculum vulgare

As the story suggests, fennel is native around the Mediterranean. It is easily found; visitors describe it as growing in the ruins of Pompei. Conspicuous and fragrant, people have been eating it for millennia. 

A member of the dill family, Apiaceae (the family is also called Umbelliferae), it can grow six feet tall. The leaves are feathery like dill. The flowers are on stalks going out from a central point, often from another set of stalks from a central point (compound), the arrangement flat across the top, a shape called an umble and characteristic of the family,. Carrots (Daucus carota) and parsley (Petroselinum crispum) also have umbels.

fennel flowers arranged in a compound umbel

Fennel has a strong pleasant scent. The scent and flavor are described as "light licorice". It is similar to anise, but distinctly "fennel."

The leaves are edible and can be used for flavoring. 

Of course there are dozens of varieties of fennel, some specialized for leaves, or stalks, or seeds, with height, color, and some flavor variation. Bronze fennel is a variety which is "bronze" in color. Here is  a young bronze fennel:

young bronze fennel plant with "bronze" leaves

They can be quite interesting--here with new leaves bronze and older leaves green

bronze fennel

Generally fennels provide feathery green leaves, very pretty in a flower bed

fennel Foeniculum vulgare

Some varieties have thickened bases on their stalks which are eaten like cooked celery. Florence fennel is one of the varieties grown for the stalks.

Fennel seeds are the part of the plant most often used and called for in cooking. They are frequent in Mediterranean recipes, whether Greek, Italian or French or from North Africa. Fennel seeds have become world-wide spices, though, and contribute to Indian cooking, Chinese (as in Chinese 5-spice powder) and Middle Eastern dishes, and seasoning blends in Tex-Mex and Mexican dishes, and were required for my Swedish mother-in-law's Swedish rye bread. 

ripening fennel seeds

The scientific name Foeniculum is the name the Romans called this plant. It is finocchio in Italian. The species epithet vulgare means common. The genus Foeniculum has five species but the others have very limited ranges; Foeniculum vulgare is the common one. It is also called sweet fennel. Kew Gardens' World Plants Online gives a distribution map for common fennel, Foeniculum vulgare link showing it native around the Mediterranean and into the Middle East but found naturalized all over the world. 

Depending on the location, fennel grows as an annual, biennial or perennials, which is to say the plant dies after one, two or several years. In my garden in Colorado, one of the few states in the U.S. where it has not been reported as naturalized, fennel is perennial. I planted one in light shade at the corner of a garden 4 years ago and it is still growing well.

fennel in midsummer

The seeds have been used since Roman times (at least) as a antidote for flatulence and discomfort from gas generally. Indian meals may end with fennel seeds for the pleasant flavor and to aid digestion. 

Roman writers spoke highly of it. Pliny the Elder in his Natural History has a section describing medicinal uses of plants learned from observing animals. When snakes shed their skins, he wrote, they "throw it off in spring with the aid of juice of fennel" and if the snake's sight is weakened, it "annoints and refreshes its eyes by rubbing on the plant called fennel or marathrum." (Pliny 41 (27)). He was enthusiastic about fennel juice to treat human eye problems. 

Traditional medicines used fennel in many forms and combinations for a wide variety of ailments. As eye medicine it has not been supported in modern tests, but German Commission E found it an effective treatment for coughs, bronchitis and gastrointestinal complaints. See medical sources for details. 

I grew fennel because there was a big swallowtail butterfly (eastern black swallowtail, Papilio polyxenes) that crossed my yard regularly. I wanted to offer it egg-laying sites as well as flowers to feed on. A quick search on hosts indicated black swallowtails will lay eggs on dill family plants, including fennel. This is an uncommon situation, where a native American butterfly successfully uses European plants as host plants. It was easy to grow a number plants dill family plants for the swallowtails.  

I grew fennel for several years and in 2024 was rewarded by seeing larvae eating my fennel. The early instars of the swallowtail were ugly, but they grew into quite handsome caterpillars. 

Lots of small caterpillars eating the fennel 

one of which became this big caterpillar with bright colors, stripes and bumps

large swallowtail caterpillar

There were more than a dozen at the beginning, and each time as I looked, fewer. I do not think the story has a happy ending; the last one vanished and I never found any pupae. 

I've maintained a big patch of fennel and looked for caterpillars each summer since, but I have not seen caterpillars again. Disappointing. 

(Note: the fennel would not agree. "Good riddance!" it says. Swallowtail caterpillars eat it!) 

fennel flowers

Fennel was never a commercial dye, but the leaves make bright clear yellows (with alum mordant on wool) and browns with iron as a mordant. 

Nice plants, fennels. They can be herbs or vegetables, pretty ornamentals, dye plants, and hosts for native butterflies. And the race, marathon, is named for a region rich in fennel.

Comments and corrections welcome.

References

Buchanan, R. 1995. A Dyer's Garden. Interweave Press, Loveland, Colorado. (or, search online "fennel dye"

CISM Europe International Military Sports Council. 2026. History-Marathon. Europe International Military Sports Council website link (Accessed 11/1/26).

Denker, J. S. 2015. The Carrot Purple and Other Curious Stories about the Food We Eat. Rowman & Littlefield. London.

Gruenwald, J., T. Brendler and C. Jaenicke, editors. 2007. PDR for Herbal Medicines. 4th edition. Thomson Healthcare Inc., Montvale, New Jersey.

National Geographic. 2008. Edible. An Illustrated Guide to the World's Food Plants. National Geographic, Washington D.C.

Pliny the Elder. Natural History. Chap 41. (27.)—The medicinal remedies which have been borrowed from animals. John Bostock translator. Online link (Accessed 11/2/26)

Royal Botanical Gardens at Kew. Foeniculum vulgare. Plants of the World Online. link (Accessed 11/2/26).Comments and corrections welcome. 

Smith, A. W. 1997. A Gardener's Handbook of Plant Names. Dover Publications. Mineola, New York.

Kathy Keeler

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