Makrut lime leaf vs Lemongrass
The short answer
Partners rather than alternatives, and a Thai curry paste generally wants both. They share a citrus register and divide it: lemongrass is grassy and lemony with real body, pounded into a paste and contributing bulk as well as aroma; makrut lime leaf is sharp, floral and purely aromatic, torn into a broth and lifted out or shredded fine and eaten. Neither supplies acidity — that is what the lime juice is for, and dishes made without it taste fragrant and flat. Dropping one is a subtraction rather than an exchange, which is the same relationship galangal has with both of them.
Side by side
| Makrut lime leaf | Lemongrass | |
|---|---|---|
| Botanical identity | Citrus hystrix DC. | Cymbopogon citratus (DC.) Stapf |
| Part used | leaf, fruit | leaf |
| Origin | Tropical Southeast Asia — the Malay peninsula, Indonesia and Thailand — where the tree has been cultivated domestically for centuries. | Maritime Southeast Asia and southern India, where Cymbopogon citratus has been grown so long that it is not known in a genuinely wild state — it rarely flowers in cultivation and is propagated entirely vegetatively. |
| Flavour notes | citric, floral, aromatic, faintly bitter | citrus, grassy, floral, clean |
| Heat | Not established | Not established |
| Flavour | Aromatic rather than tasted. Whole leaves perfume a broth and are not eaten; finely shredded, the leaf is eaten and contributes a bright citrus-floral note with a slight bitterness and a tough, fibrous texture if the shredding was not fine enough. | Mildly citric and slightly bitter, mostly delivered as aroma rather than taste. Fresh stalks are noticeably more fragrant than dried, which loses much of the top note. |
| Aroma | Intensely citric — lime peel rather than lime juice — with a floral, faintly soapy edge and none of the sourness the smell suggests. Torn, it is one of the most immediately recognisable aromas in Southeast Asian cooking. | Clean, bright and lemon-like, with a grassy green edge and a faint soapy or floral note. It carries the citrus aroma without any of the sourness, which is the reason it is not interchangeable with lemon. |
Which should you buy?
Makrut lime leaf
The choice here is fresh or frozen against dried, and it is not close. Frozen makrut lime leaf keeps almost all of its aroma for a year and goes from the freezer straight into a pot; dried leaf has lost most of the citronellal that makes it worth using and fades further within months. If the only option is dried, a curry with several other aromatics will survive it and a tom yum or a salad will not — and in those cases leaving it out and not pretending is often the better dish, since dried leaf adds a hay note the fresh leaf does not have.
Lemongrass
Buy fresh and freeze what you will not use within a fortnight. This is the rare aromatic where freezing is genuinely close to the fresh article, and it makes the dried form hard to recommend for anything but tea.
Full detail on makrut lime leaf and lemongrass, including evidence grades and sources for every claim above.