The general name "fennel" applies to two varieties of the plant: Florence fennel, or finocchio, and common fennel. Florence fennel has a bulbous base, long celery-like stalks, and delicate bright green fronds. The bulb is crunchy with a pleasantly sweet aniseed, or licorice-like flavor, and can be eaten raw or cooked. The stalks and and fronds can also be used in cooking. Common fennel is the variety of the plant from which fennel seeds are harvested. Though common fennel doesn't have a bulb, its stalks and fronds can be used like those of Florence fennel.
Choose clean, firm bulbs with no sign of browning. Any attached greenery should look fresh and bright green in color.
Florence fennel can seem unwieldy to work with at first, especially if you buy it with the stalks intact. Once you cut off the stalks (slice them close to the bulb), you'll find you have a more manageable vegetable. Next, peel the stringy fibers off the outer layer of the bulb with a peeler or sharp paring knife. Now you can cut the bulb into wedges and braise or roast it, or cut it into slices for sautéing or tossing with pasta.
Don't throw away the stalks and fronds. Add fennel stalks to a vegetable broth, especially if you plan to use the broth in a fennel dish—they lend quite a bit of anise flavor. The stalks also freeze well in plastic bags for later use. You can use the mildly anise-flavored fronds as you would a fresh herb in several ways:
You can refrigerate fennel tightly wrapped in a plastic bag for up to 5 days.