Technically, fennel seeds are not seeds at all, but actually the fruits of the sweet fennel plant, an herb which has been cultivated for culinary use for thousands of years. However, most cooks call the fruits “seeds” by convention, since they are small and usually sold in a dry form which looks exactly like a seed. There are many culinary uses for fennel seed, especially in Mediterranean and Indian cuisine. Many stores stock fennel seed, typically dry and whole. It can also be easily grown in any garden in a temperate zone, although fennel has a tendency to take over, so the plant should be encouraged with care.
There are several different cultivars of the fennel plant, which is also called Foeniculum vulgare. One cultivar, Florence fennel or finocchio, is cultivated for use as a vegetable. It produces a large bulb and thick stalks which can be cooked like a root vegetable. Sweet fennel, on the other hand, is a bulbless fennel which produces green fronds and fruits, and it is used like an herb rather than a vegetable.
Fennel is usually grown as an annual, since it does not do well in the cold. The plant smells like anise or licorice, and has feathery fronds of foliage with umbels of bright yellow flowers. The seeds are usually allowed to dry on the plant, which is gently shaken over dishes or clothes to release the seeds once they have matured fully. Once harvested, the seeds are picked through and then packaged. They can be eaten or used to start new fennel seedlings.
In Italian cuisine, fennel seed is often used in pasta sauces, for a burst of anise-like flavor. It pairs well with a number of sauce ingredients, and is typically used whole and toasted so that it will be intensely flavorful. Indian and Asian dishes also call for fennel, both whole and ground. Egypt and some North African countries incorporate fennel seed into their cuisines as well.
Since fennel seed looks and smells a great deal like anise seed, many cooks use the two interchangeably. It is a good idea to clearly label both spices to avoid confusion, since anise is more pungent. In addition, fennel aids digestion, while anise does not. As with many spices, fennel does best in an airtight container in a cool dry place, and it should not be exposed to light. Generally fennel seeds lose their potency after six months to a year, although they can be toasted to revive some of their flavor.