Overview
Fennel, Foeniculum vulgare, is a short-lived perennial hardy in zones 4a to 9b, but often grown as an annual in cooler climates. Native to southern Europe along the Mediterranean Sea, this plant in the carrot family (Apiaceae) has sweetly aromatic foliage and flavor similar to anise.
Fennel, anise, and star anise all contain the aromatic compound anethole, which give these plants their similar taste and aroma.
F. vulgare var. azoricum, Florence fennel or finocchio, has enlarged, flattened stem bases that form a bulbous structure that is eaten as a vegetable. This variety is biennial to short-lived perennial and only hardy to zone 5a.
Common fennel can grow up to 6 feet tall but is often shorter than that. The smooth, dark green leaves are finely dissected with very narrow lobes, giving a feathery appearance to the foliage (similar to that of dill). Plants produce a deep, large white tap root.
Fennel often does not bloom until its second year, but dry weather may promote bolting in first year plants. The small, bright yellow flowers are produced in terminal compound umbels at the top of the smooth, jointed, hollow stems. Each umbel section has 20 to 50 flowers on short pedicels. The flowers are very attractive to many beneficial insects including bees, wasps, lacewings, syrphid flies, and butterflies.
The seeds (botanically dry fruits) mature in the fall. Each elongate dark green to brown seed is ridged or grooved along its length. The seeds turn grey as they age. If seed is to be collected, cut the umbels should as they turn brown, before they shatter, and place them on screens or trays to complete drying.
Collect the seeds when they fall from the stems. In mild climates fennel readily reseeds, naturalizes, and may become invasive. In cooler climates it is better behaved and rarely escapes cultivation. Deadhead the plants to prevent unwanted reseeding, if desired.
Fennel is a multipurpose plant, grown both for culinary and ornamental use. The leaves, tender young shoots, stems, and seeds are used in various cuisines for flavoring and food. The fresh leaves are often used to flavor fish, egg dishes, or salads and can be used to make a tea. The leaves do not retain their flavor well when dried, however. The young shoots or “bulb” (stem bases) of Florence fennel, which have a texture similar to celery, are eaten raw or cooked in salads or as a vegetable. The seeds are commonly used whole in Italian sausage and various pastries or confections. The ground seeds are a key ingredient of Chinese five-spice powder and Indian garam masala.
Landscape Use of Fennel
The ferny foliage and upright habit of the plant makes fennel attractive when mixed with annuals or other herbaceous perennials in a cottage garden or mixed border. Use it to fill in bare spots, or plant several together as a focal point. Common fennel makes a nice backdrop for shorter plants. Combine it with butterfly weed (Asclepias tuberosa), colorful gaillardia, or coneflowers. The flowers will create a color echo with goldenrod (Solidago spp.) and black-eyed Susan (Rudbeckia hirta).
Bronze or copper leaf varieties have purplish-bronze leaves that fade to a dark green with age. These varieties compliment silver-leaved plants, such as silver sage or lamb’s ears. Fennel can be grown in large containers but typically does better in the ground because of its deep taproot.
Plant fennel in full sun in well-drained soil. In windy areas, common fennel plants grown in fertile soils may need staking. When grown in leaner soils, plants do not grow as tall so often don’t require staking. Soil fertility affects flavor, as well, with better flavor in poor soil. Once established common fennel is drought tolerant.
Florence fennel does better in more fertile soils with more even moisture than common fennel prefers. The bulbs can be blanched by mounding soil up around the base as the enlarged part develops. The largest bulbs develop in warm, sunny, moist summers.
Keep Florence fennel evenly moist, as dry conditions will promote blooming at the expense of bulb formation. Harvest the bulb once it is about the size of a tennis ball, before plants bolt.
Fennel tolerates light frost, so it can be planted in summer for fall harvest. Cut the “bulb” at the base and shoots may resprout from the root; sprouts can be eaten while small.
Fennel has few pest problems other than root rot in very wet soils. It is a host plant for anise swallowtail and black swallowtail caterpillars (especially the bronze types). The plant sap can cause skin irritation in sensitive individuals, especially when exposed to sunlight.
Propagating Fennel
Fennel is easy to grow from seed either direct sown in the garden or started indoors. Transplants also may be available. Transplant fennel seedlings before they become rootbound for best results.
Sow seeds about ¼ inch deep after the last frost in spring, or in mid-summer for a fall crop of Florence fennel. Plants can be started indoors 4 to 6 weeks before the last spring frost.
Seed typically germinates in 1 to 2 weeks. Thin plants to 4 to 6 inches apart when they reach 1 to 2 inches tall when direct sown.
Cultivars of Fennel
There are several cultivars of Florence fennel, including:
- ‘Bronze’ is a leaf fennel variety with red-bronze leaves. Slow bolting and matures in 60 days.
- ‘Dragon’ is an F1 hybrid Florence fennel variety that is uniform, late to mature and bolt resistant. Matures in 90 days.
- ‘Finale’ is an open pollinated Florence fennel variety with very large, flattened bulbs and good bolt resistance. Matures in 75 to 80 days.
- ‘Fino’ is an open pollinated Florence fennel variety best for fall harvesting. Bolt tolerant, with large bulbs. Matures in 80 days.
- ‘Grosfruchtiger’ is a leaf fennel variety with vigorous growth and sweet flavor. Matures in 60 days.
- ‘Mantovorno’ is an early Florence fennel variety with large bulbs. Matures in 75 days.
- ‘Orion’ is a hybrid Florence fennel variety with is bolt resistant and has large bulbs that hold well. Matures in about 80 days.
- ‘Preludio’ is a high yielding and uniform Florence fennel variety that is good for fall harvest. Matures in 80 days.
- ‘Purpureum’ is a leaf fennel variety with bronzy-purple foliage.
- ‘Smokey’ is a leaf fennel variety with bronzy-purple leaves. Suitable for both edible and ornamental use
- ‘Trieste’ is a French hybrid Florence fennel that is bolt resistant and matures in 90 days.
Author: Susan Mahr, University of Wisconsin—Madison
Reviewers: Allen R. Pyle, Horticulture Outreach Specialist, Bruce Spangenberg, Horticulture Outreach Specialist, UW—Madison Extension
Revised: July 2026
