“From a huge mound of dark-green, finely-cut foliage rises the vast flower-stalk, thick as a broomstick, purple tinted, topped with yellow umbellifer flowers.” – Description of Giant Fennel, Ferula communis, on Beth Chatto’s Plants & Gardens website.
Giant Fennel Abroad
I first noticed Giant Fennel, Ferula communis, in June 1987 in Corsica, growing in the Gorges de Tavignano near Corte (note 1). But my first photograph of the plant (shown above) is from many years later, from a fortnight’s cycle touring in southern France.
Giant Fennel is very impressive when in flower, when each plant has a stem two to three metres (6 – 10 feet) tall, topped with umbels of flowers in bright yellow ball-like clusters. These glow in sunshine and especially in low evening or morning light. Ferula communis is made even more dramatic by the dramatic, rocky surroundings in which it grows.
Giant Fennel, Ferula communis is a native of Mediterranean Europe, the Middle East and East Africa, as far south as Uganda, Kenya and Tanzania. It is much bigger and more dramatic than Common Fennel, Foeniculum vulgare, which is is used as a culinary herb and ornamental plant. Both plants have umbels of flowers and are members of the Apiaceae (Carrot family). You can compare pictures and descriptions of the two plants on the Flora of East Anglia website (note 2).
In its native range Giant Fennel grows on both rocky and grassy hill slopes and, in East Africa, on mountain tops, in open forest, wooded grassland (both dry and wet) and on pasture land.
Giant Fennel At Home
Giant Fennel needs well drained soil and plenty of sunshine, with some late winter and early spring rainfall during its main growth period.
Although Ferula communis is native to hot, sunny climes it can grow in parts of the British Isles. It is sometimes grown in gardens and naturalises from time to time (note 3). Giant Fennel is only hardy down to about minus 5 degrees Celsius, so a particularly cold winter could wipe out an established plant. However, human activity can do this too. Mike Crewe recounts on his Flora of East Anglia website that “a single plant beside the A11 north of Barton Mills was something of a celebrity for many years and even earned its own roadside nature reserve“, but was destroyed when the A11 was dualled.
I acquired a Giant Fennel plant several years ago and it grows in a sheltered, south facing raised bed in our front garden (note 4).
Ferula communis is a perennial plant which develops a sturdy tap root and can take several years to produce flowers. Younger plants produce feathery leaves in late winter and early spring, which yellow and die back later in the spring, leaving no trace of the plant.
This happened for several years with our plant, but this March we noticed it was starting to produce a flowering shoot.
The flower shoot grew upwards rapidly and reached full height in early April.
The umbels developed quickly too and the flowers opened from mid April and were at their peak in late April and early May. (It can be later – some websites list flowering time as early summer or even July and August.)
As I write this in early June the stems have developed their purple tint and the plant has set seed, though only on the largest umbels.
Our plant leant forward as it grew, partly to reach more light and partly as it was dashed down by heavy rain in late April and early May. I had to tie it up with a piece of string; a large stake would probably have been more elegant.
I am not sure whether our Giant Fennel will flower again. Ferula communis is often thought to be monocarpic (plants flower once, set seed then die). However, “others beg to differ, including renowned plantsman Bob Brown of Cotswold Garden Flowers“. Apparently if the flowering stem is removed before it has had a chance to set seed, the plant will live to flower again. I plan to let the seed ripen on our plant and I will need to wait until late winter to see whether our plant is still alive.
I wonder whether last year’s heat and drought, followed by winter rain and a sunny February enticed our plant to flower.
Giant Fennel: toxic and edible chemotypes
Common Fennel, Foeniculum vulgare, is a useful edible plant (both as a flavouring herb and a vegetable). But I would suggest treating Giant Fennel purely as an ornamental plant.
Sensible advice is that “though in the same family as culinary fennel (Foeniculum vulgare), Giant Fennel is considered toxic to ingest and should not be eaten“.
The Plants For A Future website says that the leaves of Ferula communis are edible and according to Wikipedia the young stems and inflorescences of Ferula communis were eaten in ancient Rome, and are still eaten in Morocco today. The Gozo In The House website says that unopened inflorescences can be steamed and served with added olive oil and vinegar.
So far, so good. But the problem is that there are two different chemotypes of Ferula communis and plants that look identical can contain different levels of secondary metabolites, making one plant toxic and the other harmless (note 5).
Other Uses
The resin contained in the roots of Giant Fennel has been used for medicinal purposes, to cure a variety of ailments. (See the Gozo In The House website for more details of medicinal uses.) The related plant Ferula assa-foetida, from southern Iran, gives us the smelly ingredient asafoetida, used in Indian cooking (note 6).
Giant Fennel stems were used to make rods and whips for disciplinary purposes. The Latin word ferire (to hit), and the Swedish färla (a disciplinary tool used in schools in the past) come from Ferula.
Hollow stalks of Giant Fennel were sometimes used as torches, as they contain a flammable pith that burns slowly and evenly without destroying the outer stalk. This is said to be how Prometheus, in Ancient Greek mythology, stole fire from the Olympian gods and to give to humanity (note 7).
We plan to dry most of our plant’s stem as an ornament but will cut a small section of the lower stem once it has dried, to use as a torch.
Grow Your Own Giant Fennel
Ferula communis seeds are available from several suppliers, such as Plant World Seeds and Special Plants Nursery. A glaucous variety of Ferula communis, ssp. glauca, is sometimes available from Beth Chatto’s Plants & Gardens as a potted plant.
Insects like the flowers – beetles and bees in Crete and in southern France. In our garden it attracted a variety of bees and flies, though the weather was rather cold and windy this spring and I would expect more insect visitors in warmer weather.
I would certainly recommend growing Giant Fennel, if you have the patience to wait for it to flower and well drained soil and a sunny, sheltered spot in your garden. The reward is worth it, I think.
Notes
Note 1 – I know this because I made a note in pencil in the guide to Mediterranean flowers that I bought there.
Note 2 – There are also other species of Ferula in the Mediterranean area, such as Ferula tingitana (Giant Tangier Fennel), which I have seen growing on the rock of Gibraltar and Ferula melitensis (Maltese Giant Fennel), which is endemic to the island of Malta.
Note 3 – On page 858 of the “New Flora of the British Isles“ by Clive Stace (Fourth Edition, 2019) mentions naturalised colonies on roadside verges in West Suffolk since 1988, in Northamptonshire (1956 – 1988 and 1996) and South Essex since 2004.
Note 4 – I’m trying to remember where it came from. I thought I grew it from seed but I now think I bought the plant in a pot from somewhere.
Note 5 – See Zucca et. al., “Isolation and characterization of polyphenol oxidase from Sardinian poisonous and non-poisonous chemotypes of Ferula communis (L.)”. Phytochemistry Vol. 90, pp 16 – 24 (2013).
Note 6 – The Ancient Greeks and Romans used silphium as a seasoning in their cookery, and as a perfume, aphrodisiac, medicine and contraceptive. It probably came from a species of Ferula, or a closely related plant. Is that plant now extinct? Pliny thought so.
Note 7 – Prometheus suffered for this. His punishment was to be tied in chains and for an eagle (Zeus’ animal familiar) to eat his liver. Every night his liver regenerated and the punishment resumed the next day.