Although commonly referred to as a ‘bulb’ cultivated fennel is not a true bulb at all but rather has thickened leaf stems.
Selection and Storage: Wrapped in a paper bag and refrigerated, fennel can last three to five days. But, as bulbs tend to dry out over time, it’s best to use them as soon as possible.
Culinary Uses: Whether served raw or cooked, fennel bulbs must be trimmed first. Cut the stalks from the top of the bulb, then remove any tough outer layers. Some recipes call for the removal of the triangular core. This can easily be done with a paring knife.
Raw, fennel is cool and crunchy. Cooked, fennel turns mellow and the flesh softens; it is wonderful alongside fish or chicken or tossed with pasta.
Fennel trimmings don’t have to be thrown away. Sprinkled fronds are regularly used as a garnish for soups, stews, and pastas. The stalks add flavor to stocks or roasted poultry or fish (stuff them into the cavity).
Information from: The Produce Bible by Leanne Kitchen