Fennel Plant Profile

Fennel plant in a garden with markers

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Fennel (Foeniculum vulgare) is often classified as both an herb and a vegetable and it can be used in many ways in the kitchen. It's also a popular plant among herbalists and has been used for thousands of years as a natural remedy, most commonly for digestive problems.

Fennel has a wonderful anise flavor that works well in both savory and sweet recipes. It's a popular ingredient in Mediterranean cuisine. The bulbs are commonly roasted or grilled or added, raw, to salads, and the feathery fronds can be added to salads and soups to impart a more delicate fennel flavor.

There are two types of fennel that you may want to grow in your garden, depending on how you plan to use it. "Florence Fennel" (Foeniculum vulgare var. azoricum) is used more like a vegetable and is grown for its bulbous stem. "Herb fennel" doesn't produce much of a bulb, and it is typically grown for its foliage and used as an herb.

Botanical Name Foeniculum vulgare
Common Names Fennel, common fennel, sweet fennel
Plant Type Perennial herb
Mature Size 4 to 6 feet tall; 18- to 36-inch spread
Sun Exposure Full sun
Soil Type Rich, moist, well-drained soil
Soil pH 5.5 to 6.8 (acidic)
Bloom Time Early summer
Flower Color Yellow
Hardiness Zones 4 to 9 (USDA)
Native Area Mediterranean

Landscape Uses

Fennel is usually grown as an edible herb in the food garden, but it also is used in meadow or cottage gardens as a border plant. The feathery, yellow-green foliage and tall stature are attractive in informal landscapes. It is also a good choice for butterfly gardens, as swallowtail caterpillars use it as a food source and pupal site.

How to Grow Fennel

Easy-to-grow fennel should be grown in full sun, in fertile, well-drained soil. It should not be planted in the same area as dill or coriander because the plant may cross-pollinate easily—seed production will be reduced. Fennel self-sows easily, so it's likely that if you plant it once, you'll see fennel popping up in your garden each spring thereafter.

Fennel is a perennial but is grown as an annual in northern climates. Treat it as an annual if winter temperatures in your area regularly fall below 15 degrees Fahrenheit.

Fennel can grow up to 5 feet tall, depending on which variety you're growing. Be sure to take its eventual size into account at planting time so it doesn't shade the rest of your vegetables. Also, it can inhibit the growth of tomatoes and beans, so avoid planting them near either of those crops.

Fennel rarely suffers from any serious problems. Aphids can sometimes be an issue, which can be treated by spraying with water to dislodge them. Avoid any kind of pesticides or oils on edible herbs.

Growing From Seeds

You can direct sow fennel seeds in your garden near your last spring frost date. Seeds should be planted 10 to 12 inches apart and will germinate in 8 to 12 days. You can also sow the seeds indoors, under lights, about four weeks before your last frost date, then harden them off and transplant them into your garden.

Growing in Containers

You can also easily grow fennel in containers. Just be sure to plant in containers that are at least 10 inches deep.

Light

This plant prefers full sunlight. Shady conditions will make it leggy and floppy.

Soil

Plant fennel in moist, fertile, well-drained soil. It prefers acidic soil (pH 5.5 to 6.8).

Water

Water deeply and regularly, but don't overwater or the plants will rot.

Temperature and Humidity

Fennel does well in all climate conditions over its hardiness range, zones 4 to 9.

Fertilizer

Fennel does not need to be fertilized during the growing season.

Harvesting

You can harvest fennel leaves as needed for fresh use. The seeds can be harvested when ripe, in late summer or early fall. The easiest way to harvest fennel seeds is to shake the seed heads over a sheet or tarp to collect the seeds. Let the seeds dry well before storing them in a cool, dark place.

Florence fennel can be harvested as soon as the base of the stem becomes swollen. Pull plants up as needed, and harvest any that are left in the ground at the end of the season before the first fall frost.

Propagating Fennel

Fennel has a long taproot and thus doesn't divide very easily. The better method is to propagate by seeds. Seed heads can be collected and planted in the garden the following spring.

Varieties of Fennel

Florence fennel (Foeniculum vulgare var. azoricum) is the type to grow if you want to harvest the bulbous stems to use as a vegetable. The leaves and seeds of this variety are also edible, so you get three uses in one plant. There are several cultivars of this variety:

  • 'Solaris' produces large semi-flat bulbs that are resistant to bolting.
  • 'Zefa fino' is ready for harvest in 80 days, bolt resistant, and very large.
  • 'Orion' is ready to harvest in 80 days and has large, thick, rounded bulbs with a crisp texture.

Herb fennel (Foeniculum vulgare) is the type to plant if you will use the plant strictly as an herb. There are two common varieties:

  • Green (Foeniculum vulgare 'Dulce')
  • Red (Foeniculum vulgare 'Rubrum')