Fennel (not native)

Foeniculum vulgare

long stem with tall flowers
Santa Inez trailhead | July 2009

Above the lower plants it towers
The Fennel with its yellow flowers;
And in an earlier age than ours
Was gifted with the wondrous powers
Lost vision to restore.
Longfellow (The Goblet of Life)

Fennel (Foeniculum vulgare), is a biennial or perennial plant in the carrot family (Apiaceae), related to common herbs such as dill, cumin, anise and parsley, as well as carrots and celery. It may reach eight feet in height and has feathery bright green leaves and green hollow stalks. In summer small bright yellow flowers grow in large, flat clusters. Fennel is host to larvae of the anise swallowtail butterfly.

In Europe and Asia, fennel has been used in traditional medicine and cooking for centuries, and it is still one of the most widely used herbal plants. In California it has escaped cultivation and become an invasive pest in many wildlands, especially near the coast. In the San Elijo Lagoon Ecological Reserve, there is an active eradication program, but the pesky plants can still be found.

Other Common Names:

sweet fennel, wild anise, biscuit root, aniseed

Description 3,4,23, 59,183,266

Fennel is a biennial or perennial herb up to 8 feet (2.5 m) tall from a deep taproot.  Many straight, jointed stems arise from a basal clump of leaves. Stems are vertically striped with green and pale green and are filled with white pith, becoming hollow with age. Branching occurs at the nodes. The plant often dies out in the fall, leaving dry stems and sending up new leaves from the base in winter or spring.

Basal and cauline leaves are green, triangular-oblong and finely dissected two to four times: the main leaf is subdivided into primary leaflets; each primary leaflet has secondary leaflets, which may have tertiary leaflets, which may have quaternary leaflets. All divisions are thread-like. Secondary leaflets are not all in the same plane, giving the leaf a fluffy appearance. Petioles clasp the stem in a conspicuous sheath. The leaves, stems, and seeds have a strong scent of anise, but true anise comes from a related plant Pimpinella anisum while true licorice comes from a plant in the pea family, Glycyrrhiza glabra.23

Flowers occur at branch ends, in large, compound flat-topped clusters, or “umbels“. Each compound umbel maybe five inches (12 cm) across and consists of smaller umbellets joined by their stems to a common point. Each umbellet has 14-27 flowers on shorter stems also originating from one point and forming a shallow umbrella-shape. Up to 30 umbellets make up the total influorescence. The bisexual flowers are bright lemon-yellow, less than 1/8 inch (2-3 mm) across. There are no sepals and the five petals are ovate, narrowing to a small terminal point; petals curl inward. Five stamens radiate beyond the petals, extending the flower diameter to nearly 1/4 inch (0.5 cm). There is one pistil with a two-chambered inferior ovary. There is a domed nectar producing surface above the ovary which supports two small styles, each with minute stigma. Flowering occurs May to September,7 although occasional flowers may be found at other times, especially on damaged plants.

Fruit is a dry, two-sided capsule that splits in half at maturity; each half contains one seed. The gray-brown, ellipsoid seeds are less than 1/4 inch (3.5-4 mm) long, compressed on one surface and with five longitudinal ribs. The two styles persist on young seeds as small beaks.  The dried seeds are aromatic and anise flavored.

tall stems with yellow mini flowers on top

Santa Inez trailhead | July 2009

leaf with multiple branches

Santa Carina trailhead | April 2016

mini yellow flowers

Santa Helena trailhead | July 2009

Distribution 7,89,183,260

Fennel is native to southern Europe and the Mediterranean region where it has been cultivated for centuries for culinary and medicinal properties.  In California, it presumably escaped cultivation in the mid-1800s.  Since then it has naturalized widely below 2000 feet throughout the western United States and Northern Mexico; it occurs sporadically in the rest of the United States. In California, it is found in open areas within many vegetation types, especially near the coast. Fennel is particularly aggressive in farmed, grazed or otherwise disturbed areas.

Fennel occurs sporadically throughout the Reserve. As recently as ten years ago, large, dense stands grew on Stonebridge Mesa and on the Santa Carina plateau. Diligent efforts by the county rangers and by Nature Collective volunteers have eliminated all but an occasional resprout or seedling. The area on Stonebridge Mesa has since been revegetated with native plants. The reduction of the fennel population is one of our success stories, but we have not yet reached the last chapter.

Classification 11,59,143

Fennel is a dicot angiosperm in the carrot family (or parsley family, Apiaceae). Members of this family are mostly herbs and are characterized by having flowers in compound umbels in which the peduncles of primary umbels radiate from one point.  In the carrot family, the umbels are themselves compound, the primary umbels consisting of many smaller umbellets. Previously, this family was called Umbelliferae, reflecting this flower structure. (The term “umbel” comes from the Latin for sunshade, referring to an umbel’s resemblance to an umbrella.) Members of this family often have a thick taproot, leaves that are pinnately dissected, and petioles that wrap part way around the stem. The two-seeded dry fruit is also characteristic.

The carrot family includes many important foods such as celery, carrots, and parsnip, and many flavorful herbs such as parsley, cumin, coriander, dill, and caraway. The same family includes two extremely toxic genera: Conium, poison hemlock, and Cicuta, a small genus called water hemlock or cowbane which is native to temperate North America and Europe but is not found in the Reserve.

Four native members of the carrot family have been reported from the Reserve:48 rattlesnake weed (Daucus pusillus), shiny lomatium (or biscuit root, Lomatium lucidum), Pacific sanicle (Sanicula crassicaulis) and California hedge-parsley (Yabea microcarpa).

Alternate Scientific Names:

Foeniculum foeniculum, Foeniculum officionale, Anethum Foeniculum

Jepson eFlora Taxon Page
field with tall stems topped with small yellow flowers

Nature Center | July 2009

dried end of plant with multiple ends

Compound umbel revealed by flower skeleton | Stonebridge Mesa | April 2016

green bush

Spring leaves among last years stalks | Santa Carina trailhead | March 2015


There are many characteristics of successful invasive plants.41,260 They come from climates similar to ours. In southern California, this restricts the origins of most of our invaders to Mediterranean climates of Europe, Asia, Africa, South America, and Australia. Invaders generally reproduce quickly and disperse widely. In their native range, they are controlled by grazers, parasites, and diseases, and these are not present in their new habitat, giving the plant an “unfair” competitive advantage over our native species.

Fennel has all these characteristics. It is native to southern Europe’s Mediterranean climate and its deep thick taproot allows it to survive summer periods without water; it reproduces both from the root crown and by seed, which are widely distributed by birds and animals. Finally, it is unpalatable to most of our large grazers, protecting the mature foliage from cattle and deer. As an additional advantage, the leaves exude substances that may inhibit germination of other plants.260 All of these properties make fennel an excellent invader.

But, there are always exceptions to generalities. One of our native swallowtail butterflies, the anise swallowtail,116,261 normally feeds on several native plants related to fennel. Fennel contains the same attracting chemicals and, since its arrival in the west coast, fennel has become an additional host species for the anise swallowtail, which feeds on both foliage and flowers. As fennel spread through the state, so did the anise swallowtail, even following the host plant into more developed habitats not previously occupied by the butterfly. More recently, as the number of fennel habitats in urban areas (mostly vacant lots) has begun to decrease, the population of anise swallowtails in developed areas is beginning to decline again.

Were we to continue this story, the next chapter would introduce the invasive Argentine ant, which protects the fennel from the butterfly,267 but that is beyond the scope of our plant guide.

field filled with tall stems and yellow flowers

Nature Center | July 2009

caterpillar climbing stem

Anise swallowtail caterpillar | Photo credit: Linda Jones

green caterpillar with black and orange dots climbing stem

Mature anise swallowtail caterpillar | Photo credit: Barbara Wallach

Human Uses

In Europe and Asia, fennel has a long history of medicinal use.262 One recent review found it used for more than 40 types of disorders. While it remains the most widely used herbal plant, few if any of the medicinal uses have been verified by modern techniques.263 

In early California, the Spaniards spread fennel branches on the mission floors to give the air a pleasant, herbal aroma.23

In the kitchen, fennel is both an herb and a vegetable. All parts of the plant have a flavor similar to anise or fennel and all parts can be eaten. The flower can be used as a garnish. The pollen, which has been called “culinary fairy dust”,264,265 is used as a spice. The seeds are often used as a flavoring for sausages, soups and stews. The leaves can be used in salads or to flavor fish and tomato dishes. The bulb can be baked, sauteed, or eaten raw. Fennel is a primary ingredient in absinthe.262

The fennel products available in the markets are generally cultivated and may be more flavorful than the wild forms. Wild fennel lacks the sweet, tender bulb used as a vegetable; this comes from a subspecies of the wild fennel, called Florence fennel, or finocchio,(F. vulgare var.azoricum).

close up of single seed pod

Last year's seed | Stonebridge Mesa | April 2016

dried up stem with multiple seed pods

Umbel of seeds | West Basin | June 2016

stem topped with multiple flowers

East Basin | July 2009

Interesting Facts 41,262

                “Prometheus moulded men out of water and earth and gave them also fire, which, unknown to Zeus, he had hidden in a stalk of fennel.” (Apollonius)

Infuriated by Prometheus’ actions, Zeus condemned him to eternal torment, chained to a rock where an eagle came daily to feast upon his liver. Prometheus was ultimately rescued by Hercules.

In the post-classical west, Prometheus came to represent human striving and the quest for scientific knowledge.

All this because fennel has hollow stems.

dense field of yellow flowers

Central Basin, west end | Aug 2009

dense field of yellow flowers

Central Basin, west end | Aug 2009

dense field of yellow flowers

Central Basin, west end | Aug 2009

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