
Fennel seeds are the dried schizocarp fruits of Foeniculum vulgare, an aromatic Apiaceae herb, used whole or ground as a licorice-scented spice.
Sweet and licorice-like, driven by anise-scented anethole, with a mild, warm aroma that is gentler than that of anise or star anise.
Serving as a small aromatic accent, they are lightly crushed or toasted to release their volatile oils, then infused into a spirit or syrup, or scattered as a garnish; a pinch is enough, as they contribute aroma rather than body or sweetness.
Another anethole-bearing spice such as anise or star anise reproduces the defining licorice aroma; a non-licorice seed like caraway will not, and any trivial sweetness can be rebalanced with a touch of syrup.
Anise seed
Both are Apiaceae seeds dominated by anethole and taste of licorice, but fennel seeds are larger, more oval and typically milder and sweeter, while anise seed is smaller and more intensely aniseed.
Caraway seed
Fennel and caraway are both crescent-shaped Apiaceae seeds of similar appearance, but fennel is sweet and licorice-scented from anethole, whereas caraway is earthy and peppery from carvone.
Fennel seeds are the small, grooved dry fruits of the plant, 4–10 mm long, though they are commonly called seeds. Their anise/licorice character comes from volatile oils, chiefly trans-anethole, alongside estragole, fenchone and limonene.
Whole seeds hold their aroma far longer than pre-ground; keep them sealed away from heat and light, and grind or crush close to use.
Fennel is generally considered indigenous to the shores of the Mediterranean and, as a member of the Apiaceae family, is now cultivated and naturalised widely.