Fennel: Discover the Origins and Secrets of this Versatile Plant

Fennel is a fascinating plant that has been cherished in the Mediterranean for its culinary and medicinal properties. Whether you want to grow it as a vegetable or use it as a herb, this guide will provide you with valuable insights on fennel’s origins, care, and propagation.

Two fennel plants on a saucer

Fennel, scientifically known as Foeniculum vulgare, has been utilized as a medicinal herb for thousands of years. In this article, we will delve into the origins of this versatile Mediterranean plant and provide helpful tips on how to care for it, including overwintering and propagation.

Fennel: Characteristics and Ancient Origins

Fennel has a rich history as a vegetable, herb, spice, and medicinal plant in the Mediterranean region. It was introduced to us by the Romans when it was primarily used for its medicinal properties. While the exact origin remains unknown, it is believed to be native to the Mediterranean region and eastern Asia. The ancient Greeks used fennel mainly as a medicinal herb but also incorporated it into their cuisine. Fennel belongs to the umbelliferae family (Apiaceae) and is closely related to anise, caraway, and dill.

A sprouting fennel plant in the ground

Fennel grows as a biennial to perennial shrub with thick branched stems that can reach impressive heights of 120 cm to 200 cm. In the first year, the stems are 50 to 100 cm tall and develop scale-like features. The plant only flowers in the second year. Fennel forms a rough root that can extend deep into the soil under favorable conditions.

The feathery green leaves, known as fennel fronds, resemble dill in appearance. These fronds can be harvested and dried. The branched stems are covered by a fleshy leaf sheath. Between July and September, the fennel plant blooms, producing numerous small yellow flowers. These flowers attract hoverflies and bees with their abundant nectar during the summer. After pollination, the initially blue-green seeds develop, becoming long and grooved. They ripen between September and November, turning brown and falling off.

Is Fennel a Vegetable?
Fennel encompasses three varieties, each used in different ways: common fennel, sweet fennel (used as a herb), and bulb fennel (also known as Florence fennel or finocchio), which is treated as a vegetable. With the resurgence of heritage varieties and modern breeding techniques, the diversity of fennel species is greater than ever before.

Many small yellow fennel flowers attracting insects

Caring for Fennel: Watering, Fertilizing, and More

Fennel is a low-maintenance plant that requires minimal attention, aside from watering during summer. After planting, there are a few key measures to ensure successful growth. Regularly weed around your young fennel plants to eliminate any competition for water and nutrients. Applying a mulch layer of plant materials, such as lawn clippings, can prevent weed growth and reduce water evaporation. However, as organic matter breaks down, it fixes nitrogen, necessitating additional fertilizer application to maintain optimal nutrient levels.

Fennel also thrives when provided with higher amounts of potassium. You can achieve this by using a plant-based slow-release fertilizer, such as Plantura Tomato Food. Work this granular fertilizer into the soil surrounding the fennel during transplantation or direct sowing. The nutrients from the fertilizer are released gradually over the following weeks, promoting the plant’s growth and enriching the soil’s nutrient content.

Only one pest threatens fennel – the caterpillar of the old world swallowtail butterfly. However, the damage caused by these caterpillars is minimal and is later compensated with the presence of beautiful cream and blue-colored butterflies in your garden.

A colorful butterfly approaching yellow fennel flower

Is Fennel Winter-Hardy?

Interestingly, although more developed tuberous fennel plants are not winter-hardy, younger plants can tolerate short-term sub-zero temperatures of up to -4 °C. Since vegetable fennel is typically grown annually for its tender bulb, overwintering is usually unnecessary. Only if you wish to harvest seeds should bulb fennel plants be overwintered. Common fennel and sweet fennel are winter-hardy varieties that can withstand temperatures below -20 °C in our region.


Fennel can be propagated through seed sowing. To collect fennel seeds, it is essential to identify whether you have sweet fennel or bulb fennel. The latter usually only flowers in the second year and must be overwintered frost-free for seeds to develop. To overwinter fennel, select 10 to 15 healthy bulbs, cut back the leaves to about 20 cm, and pot the plants. Place them in a cold house or conservatory, ensuring that humidity levels remain moderate and avoiding excessive watering to prevent fungal diseases.

In the following spring, transplant the fennel outdoors after the last frost. It will quickly begin flowering, and the fennel seeds will ripen by autumn. Sweet fennel, on the other hand, produces plenty of flowers and seeds in the first year after sowing, with a usually larger harvest in the second year. Remove brown seed stalks and allow them to dry since ripe fennel seeds have a tendency to fall off. These seeds can germinate for up to one or two years.

A pile of fennel seeds on a rustic wood

Tip: Sweet fennel, bulb fennel, and common fennel can interbreed due to their close relationship. When propagating a specific fennel variety, it is important to avoid doing so simultaneously with another variety.

Fennel is a versatile plant that adds aromatic and healthy bulbs to a wide range of dishes. Explore planting fennel in your garden for a delightful addition to your culinary adventures.