Liquorice root vs Fennel seed
The short answer
Both taste of anise and neither owes it to the same compound, which is the useful part. Fennel is dominated by anethole, sweet and volatile, and is a seed used as a spice. Liquorice root is dominated by glycyrrhizin, which is fifty times sweeter than sugar, and the anise impression is a secondary effect. Liquorice also raises blood pressure and depletes potassium at intakes people genuinely reach, which fennel does not.
Side by side
| Liquorice root | Fennel seed | |
|---|---|---|
| Botanical identity | Glycyrrhiza glabra L., Glycyrrhiza uralensis Fisch. ex DC. | Foeniculum vulgare Mill. |
| Part used | root | fruit, seed |
| Origin | West Asia and the eastern Mediterranean for G. glabra, with G. uralensis native to northern China and Mongolia. Cultivation and wild collection extend across a broad temperate band from Spain to China. | The Mediterranean basin, where the plant grows wild and from which cultivation spread eastwards early. |
| Flavour notes | sweet, earthy, anise-adjacent, lingering | sweet, anise, grassy, green, cooling, faintly bitter |
| Heat | Not established | Scoville does not apply |
| Flavour | Intensely and persistently sweet, with an earthy, slightly bitter woodiness behind it and a cooling finish that lingers well after other flavours have gone. The sweetness arrives slowly and outlasts everything, which is the property that makes it useful and also the reason it is easy to overuse. | Sweet and liquorice-like but noticeably lighter and grassier than star anise or aniseed, with a mild bitterness in the finish and a faint cooling quality. It is sweet enough to read as a dessert spice and green enough to work in a sausage, which is an unusually wide range. |
| Aroma | Sweet, earthy and faintly anise-like, with a woody base. Much quieter than star anise and quite different in character — the anise note is a suggestion rather than the dominant impression. | Sweet and anise-like with a clear green, grassy freshness underneath it, and a light warm-spicy note when toasted. |
Which should you buy?
Liquorice root
Buy the root, in sticks or chips. The reason is control rather than freshness, which makes this different from most whole-versus-ground cases here: liquorice keeps its sweetness for years in either form, but the sweetness is slow to arrive and keeps building, so the ability to taste a simmering stock and lift the piece out is worth more than convenience. Ground root cannot be retrieved, mills poorly because the material is fibrous, and carries more of the woody bitterness because nothing is left behind. The powder earns a place in a dry rub or a dough where a stick cannot go, and almost nowhere else.
Fennel seed
Buy whole. Fennel is cheap, grinds easily, is much improved by toasting first, and is used whole in most of its traditional applications anyway — sausage, bread, tempering and mukhwas all want the intact seed. Ground fennel loses the green top notes that distinguish it from plain aniseed within months, which removes most of the reason to choose fennel in the first place.
Full detail on liquorice root and fennel seed, including evidence grades and sources for every claim above.