Reference point
Crush a fresh leaf of húng lủi garden mint and smell it at once.
Do this before you read on. An entry only works when you have just smelled the thing.
Cool, sweet, green — but not icy like peppermint. This is the most important distinguishing point, and the one almost everyone overlooks.
Peppermint contains menthol, which activates the cold receptors and makes you feel a bite of cold. This mint has almost no menthol, so it gives coolness without cold. The same genus, two chemical directions, two experiences that differ in kind.
It evaporates quickly, so it belongs to the top stage. Chopped and left for five minutes, it has lost most of its smell.
A note on the name: the market name húng lủi does not correspond to a single species. See the scientific note below.
How to smell it
Crush a leaf and smell it. If you have peppermint or a mint sweet, smell that straight afterwards. Pay attention to separating the two: the smell is similar, the sensation of temperature is completely different. It is a good exercise for understanding that the nose and the trigeminal nerve are two separate systems.
Why this one is hard
Because in many contexts both plants are simply called mint. The name lumps together two things that are chemically different.
Don’t confuse with
This entry
Garden mint
Green family
The same mint genus but different chemical directions. Peppermint contains menthol, so it gives an icy cold; this mint has almost no menthol, so it is cool without being cold. Tell them apart by the sensation of temperature, not by the name of a molecule — the dominant compound of this mint depends on the variety.
Scientific note
Peppermint contains menthol, which activates the cold receptors. This mint does not, and that is the whole difference in sensation between the two.
But what its dominant compound is has no neat answer, because the name itself is unstable. The reference work Những cây thuốc và vị thuốc Việt Nam identifies it as Mentha crispa and reports carvone at about fifty to sixty percent. The reference work Cây cỏ Việt Nam gives Mentha aquatica. Some other sources give Mentha arvensis, while herb sellers and producers usually give Mentha spicata. Some sources report carvone as dominant, others dihydrocarvone together with limonene and cineole.
It is a living example of what we wrote in the article on species names: one market name can cover several different species, and buying at two markets can get you two different plants.
So don’t use this entry as a reference for a particular molecule. Use it as a reference for a sensation: cool without cold. That sensation is stable across every variant, while the composition is not.
That is also why this entry has no compound block like most others. We could list carvone there, but doing so would assert exactly what we have just said is not settled. The carvone page mentions this case, with all the necessary caution.
In Vietnamese life
This mint is an essential accompaniment to many southern Vietnamese rolls and salads. It is almost never cooked — its smell does not survive heat, and Vietnamese cooks have long known it.