Fish mint vs Vietnamese coriander
The short answer
Two creeping herbs of wet ground eaten raw in South-East Asia, sold in the same markets and from different plant families. Vietnamese coriander has narrow leaves and smells of coriander leaf with a peppery edge. Fish mint has heart-shaped leaves and smells fishy, from a compound the other does not have; its rhizome is eaten too, which the other’s is not.
Side by side
| Fish mint | Vietnamese coriander | |
|---|---|---|
| Botanical identity | Houttuynia cordata Thunb. | Persicaria odorata (Lour.) Soják |
| Part used | leaf, rhizome, stem | leaf |
| Origin | East and South-East Asia. The laboratory study of its smell calls it native to China, Korea, Japan and South-East Asia, and the Flora of China gives the range of the genus as East and South Asia. | Mainland Southeast Asia — Vietnam and its neighbours — where it grows wild and semi-wild along ditches and paddy margins. |
| Flavour notes | fishy, soapy, green, citrusy, metallic | coriander-like, peppery, citric, waxy, sharp |
| Heat | Scoville does not apply | Scoville does not apply |
| Flavour | A paper on the plant’s volatiles describes the rhizome as eaten in south-west China as mildly fishy, crisp, tender and juicy, with a slightly sweet aftertaste. It gives this as common knowledge and reports no tasting. | Hot-peppery and coriander-like, with a faint tongue-prickling bite and a slightly astringent finish. Eaten raw, it cuts through fat and richness — the reason it is served with duck, eggs and coconut broths. |
| Aroma | Fishy, and the two parts differ. A trained panel of 21 at a German food-chemistry institute smelled freshly chopped rhizome and leaf and rated nine notes. In the rhizome fishy was the strongest, followed by soapy, geranium leaf, citrus, metallic, coriander leaf and green. In the leaf green and grassy came first and fishy second, then soapy, geranium leaf, metallic, coriander leaf and citrus. Every note but the green one was stronger in the rhizome. | Coriander-like and sharper: green, soapy-citrus, with a waxy, almost metallic high note. Where coriander is soft, rau răm is pointed. |
Which should you buy?
Fish mint
Used fresh and whole or chopped. Nothing read describes a ground or dried form used in cooking.
Vietnamese coriander
Fresh, always, and a pot rather than a bunch if you use it often: the stems root in a glass of water and the plant grows fast in warmth. Dried rau răm is barely worth buying, because the dishes it belongs in eat it raw.
Full detail on fish mint and vietnamese coriander, including evidence grades and sources for every claim above.