How to Grow Fennel

Fennel is a diverse herb and vegetable. The seeds, leaves, stems and bulbs can all be consumed. Fennel can be eaten raw or cooked and adds a unique flavor to a variety of culinary contraptions. What’s more, fennel is an easy to plant and care for. It grows wild as an invasive species on roadsides and hillsides in many coastal areas but wild fennel is quite different from domestic fennel and does not produce bulbs. Here are some tips on how to grow fennel in your home garden.


Fennel is a perennial that should be planted after the last frost of the winter. Seeds germinate when soil temperatures are between 50° F and 70° F. It takes up to 100 days to mature.

Fennel is relatively hardy and can be grown year round in zones 5-10. Grow as a perennial in colder zones.

Plant fennel in an area of the garden that receives full sun exposure and has loose, deep soil. Best to grow fennel away from other garden vegetables because it will cross pollinate, making for mixed flavor results, at best. Fennel grows back by itself each year, so dedicate a space in the garden to fennel if you plan to keep it going.

Fennel can be grown in large pots as well. It produces a long taproot and needs sufficient soil space to accommodate it, so containers are not always sufficient.

Plant fennel in loose, well draining soil. Enrich the soil with mature compost but it doesn’t need super fertile for the fennel to thrive. Test the soil to be sure it has a pH of 6.0 – 7.5.

Fennel does not transplant well. Direct sow your fennel seeds after the last frost of the season. Sow seeds about an inch deep and 10-12 inches apart. Rows should be spaced 3 feet apart. Water well until seeds germinate, usually within 7 – 14 days. You can also plant seeds closer together and thin once they become established.

If you choose to grow fennel in containers, be sure they have at least 12 inches and/or 5 gallons of soil in which to thrive. Fennel develops an extensive root system that will quickly outgrow small containers.

Fennel should be watered regularly, about twice per week during dry spells. Keep the soil moist but never soggy. Avoid root rot by never over watering. Best to let the soil nearly dry out before giving it a good, long soak.

Use a few inches or organic mulch, like straw or wood chips, around each fennel plant. This will keep weeds down and preserve moisture in the soil.

Fennel bulbs grow at the base of the plants just above the soil surface. For a better flavor and to keep the bulbs from turning green, build up a mound of soil around the bulb as they develop to block out the sun. This is called blanching and your fennel bulbs will taste much sweeter for the extra attention.

Fennel is not a target for most pests. However, keep an eye out for aphids and whiteflies. They can usually be kept under control by hose blasting them or using insecticidal soap spray. Be sure to spray and rinse in the morning to allow the plant’s foliage to dry out throughout the day. This will limit the risk of mold.

Fennel takes about 80-100 days to mature. If you want to harvest fennel for both its seeds and bulbs you’ll need to have multiple plants. Bulbs are harvested before the plant goes to seed. Hot weather and less watering will encourage the plant to bolt.

Harvest bulbs when they get no larger than a tennis ball. Be sure to harvest before the plant goes to seed or the flavor will be ruined. Slice the bulb and stalks off right at the soil line.

You can harvest fennel leaves throughout the growing season, but best to clip only a few at a time or else the plant’s growth and quality of the bulbs may be hindered.

Harvest fennel seeds in the fall as the plants turn brown. They may shake loose easily from the plant into a paper bag or other container. Even if you don’t plant to use the seeds as herb, you may want to harvest the seeds in order to keep your fennel crop under control. You can also wrap the branches in cheesecloth and cut them from the plant. Hang dry and then thresh out the seeds.

Use freshly harvested fennel bulbs within 3 days for best flavor.

Store completely dried fennel seeds in an airtight container.

Fennel is a good source of potassium, calcium, vitamin C and fiber.

Do you have tips on how to grow fennel? Let us know in the comments section below.

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