Fennel and black licorice are two separate plants. The licorice plant is a legume, and its root is used as a flavoring and spice. Fennel is an aromatic plant with edible stalks. It is also used as an herb. Although fennel tastes like black licorice, it has little else in common with licorice. Enjoy each plant for its distinct properties.
Fennel, or Foeniculum vulgare, is a tall, flowering perennial. There are many varieties of fennel, including German, Russian, Persian, Indian, Japanese and Romanian. According to the "Encyclopedia of Herbs," the United States imports the majority of its fennel from Egypt. Dried fennel seeds have both medicinal and culinary uses. Fennel can also be eaten raw or cooked. Many people add the stalks and the bulbs to their salads. A distinct characteristic of fennel is that it often attracts shallowtail anise butterflies, to the delight horticulturalists and botanists.
Licorice is a plant whose root and rhizome yields an essential oil used for medicinal and flavoring purposes. Its distinct flavor comes from a compound exclusive to licorice called glycyrrhizin. Licorice root is used to treat ailments including sore throat, bronchitis, stomach ulcers and viral infections, although there is no substantive evidence that licorice can effectively treat any condition, according to the National Center for Complementary and Alternative Medicine. As a matter of fact, evidence suggests that large amounts of glycyrrhizin can cause sodium and water retention, low potassium and high-blood pressure. Large amounts can also cause preterm labor. Consuming licorice in tandem with diuretics can lead to potassium deficiency.
Black licorice is a candy flavored with licorice-root essential oil, glybcyrrhizic acid or anise oil. Although many fruit-flavored licorice candies are on the market today, only black licorice is meant to taste like licorice root.
Given that they are distinctly different, why is it that fennel and licorice are often confused for one another? The answer is that fennel and glycyrrhizin have very similar flavors. Moreover, a third food additive, anise, also tastes and smells quite similar to both licorice and fennel, leading to further confusion. In essence, anything with this particular flavor could contain any of these plants or a combination.