Fennel - Similar Species

Similar Species

Many species in the family Apiaceae (formerly Umbelliferae) are superficially similar to fennel, and some, such as poison hemlock (see below), are toxic. It is therefore unwise, and potentially extremely dangerous, to use any part of any of these plants as a herb or vegetable unless it can be positively identified as being edible.

Dill, coriander and caraway are similar-looking herbs but shorter-growing than fennel, reaching only 40–60 cm; dill has thread-like, feathery leaves and yellow flowers; coriander and caraway have white flowers and finely divided leaves (though not as fine as dill or fennel) and are also shorter-lived (being annual or biennial plants). The superficial similarity in appearance between these may have led to a sharing of names and etymology, as in the case of meridian fennel, a term for caraway.

Cicely, or sweet cicely, is sometimes grown as a herb; like fennel, it contains anethole and therefore has a similar aroma, but it is lower-growing (to 2 m), has large umbels of white flowers, and its leaves are fern-like rather than threadlike.

Giant fennel (Ferula communis) is a large, coarse plant, with a pungent aroma, which grows wild in the Mediterranean region and is only occasionally grown in gardens elsewhere. Other species of the genus Ferula are also commonly called giant fennel, but they are not culinary herbs.

The most dangerous plant which might be confused with fennel is probably hemlock (poison hemlock). Hemlock tends to grow near water or in consistently moist soil, is tall (0.75 – 2 m), has purple blotches on the main stem, and is heavily branched, with small umbels of white flowers. A useful test to distinguish between it and fennel is to crush some leaves and smell them. Fennel smells like anise or liquorice, whereas the smell of poison hemlock is often described as mouse-like or musty. But take care: coniine, a toxin contained in poison hemlock, can be absorbed through the skin, so do not do this "smell test" with bare hands (and avoid touching your eyes or mouth) unless you can wash them immediately afterwards.

Fennel is found growing, in North America, in the same habitat and alongside natives osha (Ligusticum porteri) and Lomatium species, useful medicinal relatives in the parsley family.

Lomatium (which closely resembles hemlock, and can be very difficult to distinguish from it) is an important historical food plant of Native Americans, known as 'biscuit root'. Most Lomatium species have yellow flowers, like fennel, but some are white flowered and closely resemble poison hemlock. Most Lomatium spp. have finely divided, hairlike leaves; their roots have a delicate rice-like odor, unlike the musty odor of hemlock. Lomatium species tend to prefer dry rocky soils devoid of organic material.

Osha, Ligusticum porteri, has white flowers and finely-divided leaves, similar to poison hemlock, but not as fine as fennel or dill. The leaves are intensely fragrant with a "spicy celery" odor, unlike the musty or "mousy" smell of poison hemlock, but care should be taken in checking this characteristic, as the fresh juice (of the roots) is an astringent and can cause blistering.