Yes, fennel and celery are closely related. Both belong to the Apiaceae family, commonly called the carrot family, which contains roughly 3,780 species across 434 genera. They share the same family, the same order (Apiales), and even the same tribe (Apieae), but they split at the genus level: fennel is Foeniculum vulgare and celery is Apium graveolens. Think of them as botanical cousins rather than siblings.
How Close the Relationship Is
In plant taxonomy, family is a broad grouping. Sharing a family means fennel and celery have a common evolutionary ancestor, but they’ve had plenty of time to diverge. A useful comparison: dogs and foxes are in the same family (Canidae) but are clearly different animals. Fennel and celery are similarly distinct plants that still carry recognizable family traits.
Both also belong to the tribe Apieae within Apiaceae, which puts them a step closer than some other relatives. They share that tribal grouping with dill, parsley, and coriander. The European genetic resources program tracks nine Apiaceae genera together, including fennel, celery, carrot, parsnip, caraway, chervil, coriander, dill, and parsley, reflecting how tightly this group of food plants is linked.
What They Have in Common
The Apiaceae family has a few hallmarks you can spot once you know what to look for. The flowers are small, bisexual, and cluster together in flat-topped umbrella shapes called umbels. Each tiny flower has five petals and five sepals. The leaves tend to be feathery or finely divided and attach to the stem with a sheath at the base. Stems are often hollow or at least have a pithy interior.
Both fennel and celery fit this template. They produce umbrella-shaped flower clusters, have feathery or compound leaves, and grow upright with thick, crisp stems. Both are native to the Mediterranean region, where the majority of Apiaceae species originated, and both have been cultivated since ancient times as food and medicine.
Why They Taste So Different
Despite the family resemblance, fennel and celery taste nothing alike, and the chemistry explains why. Fennel’s signature licorice flavor comes almost entirely from a single compound called trans-anethole, which makes up 84 to 86 percent of fennel’s essential oil. Smaller amounts of fenchone (7 to 9 percent) and limonene (about 3 percent) round out the profile, but anethole dominates.
Celery gets its characteristic earthy, savory flavor from a completely different set of chemicals. Its essential oil is built around phthalides, limonene, and compounds like beta-selinene and spathulenol. Phthalides are responsible for that distinct “celery” smell that’s hard to describe but instantly recognizable. The two plants share limonene as a minor component, but their dominant flavor molecules are unrelated, which is why fennel tastes like anise and celery tastes like, well, celery.
Other Relatives You Already Know
The Apiaceae family is packed with familiar kitchen staples. Carrots, parsley, dill, cilantro (coriander), cumin, caraway, parsnips, and chervil all belong to the same family. If you line up these plants in your garden, you’d notice the family resemblance in their flowers and leaf structure even though their flavors, colors, and the parts you eat vary widely.
Most of these species are native to the Mediterranean or southwestern Asia, and many have been used as both food and medicine for centuries. The diversity within a single plant family is striking: carrots are grown for their roots, celery for its stalks, fennel for its bulb, and parsley, dill, and cilantro primarily for their leaves or seeds.
Dangerous Lookalikes in the Family
One practical reason to understand this family relationship is safety. Apiaceae also includes poison hemlock and western water hemlock, both of which can be lethal. Their flowers form the same umbrella-shaped white clusters, and their leaves have the same finely divided, fern-like appearance that makes edible members of the family look so appealing.
Poison hemlock is frequently mistaken for wild carrot, wild parsnip, or wild parsley. You can tell it apart by the profuse purple or reddish-purple spots on its smooth, hairless stem. It also produces a distinctly unpleasant smell, often compared to mouse urine, that becomes especially noticeable when the leaves are crushed. If you’re foraging for wild fennel or any wild Apiaceae plant, these identifiers are critical. Western water hemlock shares the same umbrella-shaped white flowers and poses the same risk of confusion.
The bottom line for anyone gathering wild plants: never eat a member of this family unless you can positively identify it. The edible and deadly species look remarkably similar at a glance, and the consequences of a mistake are severe.
Nutritional Differences
Fennel and celery are both low-calorie vegetables, but fennel is notably more nutrient-dense. A single raw fennel bulb provides over 7 grams of fiber and is a good source of potassium, calcium, and phosphorus. Celery is mostly water (about 95 percent) and delivers far less fiber per serving, though it still contributes potassium and vitamin K.
In the kitchen, fennel’s bulb is the main attraction, usually sliced raw into salads or roasted until caramelized. Celery is most often eaten raw as a snack or used as a base flavor in soups and stocks. Despite their shared ancestry, they’re not interchangeable in recipes. Fennel brings sweetness and anise notes, while celery adds a savory, slightly bitter backbone.