Whether you grow your own fennel in your garden or picked up more than you can use on a trip to the grocery store, freezing extra fennel is a great and relatively simple way to preserve it for later. The three parts of the fennel, the bulb, stalks and leaves, should each be frozen separately. Fennel has a taste similar to licorice. Although the large, white bulb usually takes center stage in recipes, the delicate leaves work as an herb, and the stalks are good for flavoring soups and stocks.
Cut the green stalks from the white bulb, and remove the leaves from the stalks.
Place the leaves in an ice cube tray in quantities you'd need for a recipe, such as 1/2 teaspoon. Cover the leaves with water, and place in the freezer.
Chop the stalks. Place the chopped stalks in another ice cube tray in equal quantities, as with the leaves. Cover with water and place in the freezer.
Boil a pot of water on the stove. As the water heats, cut the white bulb into quarters or eighths.
Fill a bowl halfway with ice, and add cold water until the ice is floating.
Place the fennel pieces in the pot of water when it is boiling. Allow the fennel to cook in the boiling water for 30 seconds.
Transfer the fennel bulb sections to the ice cold water until they cool.
Place the fennel sections in a freezer-safe plastic bag, and label the bag.
Transfer the cubes of fennel leaves and the cubes of fennel stalk to separate freezer bags when the water in the ice cube trays has frozen. Label the bags with the date and the amount of fennel leaves or stalks contained in each cube.
If you prefer, slice the fennel instead of sectioning it if before boiling and rapidly cooling it, a process called blanching.
Defrosted fennel will not retain its crisp character, although the taste will be unchanged.