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Ask a Master Gardener: How to grow fennel to use as a vegetable and an herb

by Peter Sutter | January 7, 2023 at 4:00 a.m.

I hope you enjoyed the warm weather we had a few days ago. Freezing weather one week and 60-70 degrees the next. You have to love Mid-Missouri weather.

I would like to introduce you to both a vegetable and an herb, depending on which variety you grow.

Fennel. First off, I will tell you I have only grown fennel once before, but I have thought about it and decided this year I will plant some again. After inquiring around and doing a little research, this is what I came up with: The type of fennel you choose to grow will depend on what part of the fennel plant you wish to use -- the bulb, the fronds or the seeds.

Florence Fennel is grown for its bulbous stem, which can be eaten raw, grilled or baked. It is also possible to eat the thicker stalks which sprout from the bulb, as they are similar to celery.

Herb fennel does not produce the same bulbous stem. It is grown for its delicate leaves, which are used as an herb. Herb fennel also produces seeds which have a licorice-like flavor (as does the rest of the plant) and are used for seasoning. We are going for the bulb, so be sure you get Florence Fennel.

Fennel does best in cool weather--not hot, but not freezing. Although you can plant the seeds directly into the garden after the soil has warmed, transplants are helpful to get a head start in spring; we all know how fast Mid-Missouri summers can heat up.

It takes about three months for fennel to produce the bulb, so do the math and we will need to start the seeds toward the end of February to harvest late spring to early summer.

Plant fennel transplants in a sunny spot. Like most garden plants, they like well drained soil with compost mixed in. Space the plants about 12 inches apart. Keep the bed moist and feed the fennel plants about every two to three weeks with a liquid fertilizer.

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, after the bulb grows to about 2 inches in length, build up a mound of soil around the bulb as they develop to block out the sun. This is called blanching; your fennel bulbs will taste much sweeter for the extra attention.

Snip off any flower stalks that may form to prevent the bulb from splitting. When it's time to harvest, use clippers to snip under the bulb and cut the taproot.

Your fennel will be ready when the bulbs are about 2 inches across, up to about the size of a tennis ball. Cut just below the bulb at ground level.

Harvest leaves as needed at any time (just don't take to many at once).

Harvest flower heads after seeds have formed and the flower head has died.

Extract seeds and dry them in a cool, dry location. Fennel doesn't keep very well, especially with the leaves still attached. Remove the leaves and use to flavor soups, stews or stock. If the leaves are left on the plant, they will suck out the moisture and the bulb will become soft.

Happy Gardening!

Peter Sutter is a lifelong gardening enthusiast and a participant in the MU Extension's Master Gardener program. Gardening questions can be sent to [email protected].

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