Vietnamese coriander, or rau răm, is a Southeast Asian knotweed with a flavour like coriander with pepper and lemon. It is the essential leaf in laksa and Vietnamese chicken salad.
What it is¶
Vietnamese coriander is not a coriander at all, nor a mint, although it is sometimes sold as "Vietnamese mint" and "hot mint". It is a creeping, water-loving perennial in the knotweed family, a relative of sorrel and buckwheat, with narrow, pointed leaves often marked with a dark, chevron-shaped blotch in the middle.
In Vietnam it is rau răm. In Malaysia and Singapore it is daun kesum, and because it is indispensable in the soup there, it is often sold as laksa leaf. In Thailand it is phak phai, and in Laos phak pheo.
Its name in English comes from the flavour: several of the same aroma compounds that give coriander leaf its character are present, alongside a peppery heat that coriander lacks.
Origins and history¶
Persicaria odorata is native to the warm, wet regions of mainland and maritime Southeast Asia, where it grows along ditches, ponds and paddy margins and has been gathered and cultivated as a food plant for a very long time. It is used across Vietnam, Cambodia, Laos, Thailand, Malaysia, Singapore and Indonesia.
It travelled with the Vietnamese and Malaysian diasporas and is now grown commercially in Australia, the USA and Europe for the restaurant trade, and sold in Asian supermarkets worldwide.
Flavour and aroma¶
Rau răm tastes like a sharper, more aggressive coriander: green and citrusy, with a peppery, slightly hot bite that builds in the mouth and a faintly soapy, metallic finish. People who find coriander soapy (see why coriander tastes of soap) often react the same way to rau răm, as the leaves share some of the same aldehydes.
It is stronger than coriander and keeps its flavour a little better when briefly cooked.
In the kitchen¶
Rau răm is overwhelmingly used raw, as part of a dish rather than a garnish.
- Vietnamese chicken salad. Gỏi gà (or gà xé phay) is poached, shredded chicken tossed with shredded cabbage, onions, lime, fish sauce and a large handful of rau răm. It is the herb's classic partner.
- Herb plates. Rau răm sits alongside mint, thai basil, tía tô and culantro on the herb plates served with noodle soups, rolls and grilled meats.
- Balut. The fertilised duck egg hột vịt lộn is always eaten with rau răm, salt, pepper and lime.
- Laksa. In Malaysia and Singapore, shredded daun kesum is essential in both the coconut curry laksa of Singapore and the sour, tamarind-based Penang asam laksa, where it is added generously to the finished bowl.
- Salads and rolls. Add leaves to fresh spring rolls, papaya salads and banana-blossom salads, and use them with raw or seared beef.
💡 Pick the leaves, not the stems
Strip the leaves from the stalks, which are wiry and tough. Use leaves whole or roughly torn; they bruise quickly once chopped.
Buying and storing¶
Rau răm is sold in bunches in Asian grocers. Choose crisp stems with bright leaves. It wilts quickly: stand the bunch in a glass of water, loosely cover with a bag and refrigerate, or wrap in damp paper towel. It will keep for three to five days.
It does not dry or freeze well. However, stems stood in water will usually root within a week or two, so a bunch can become a plant. See storing fresh herbs.
Substitutes¶
Coriander leaf is the nearest substitute, perhaps with a few leaves of mint or a little black pepper to mimic the bite. In laksa, a mixture of coriander and mint works acceptably. Culantro shares the same family of aromas but is stronger.
Pairs well with¶
Chicken, duck and eggs; beef; prawns and fish; lime, fish sauce and palm sugar; chillies; mint, thai basil and coriander leaf; coconut; tamarind; cabbage and green papaya; rice noodles.
Growing your own¶
Vietnamese coriander is one of the easiest tender herbs to grow, provided it is kept warm and wet.
- Starting. Root a few stems from a bought bunch in a glass of water, then pot them up. Plants are also available from herb nurseries. Seed is rarely produced in cool climates.
- Conditions. It thrives in moist, rich compost, even standing in a saucer of water, in bright light but out of scorching midday sun.
- Winter. It is not frost-hardy and sulks below about 10°C. In Britain, grow it in a pot outdoors in summer and bring it inside to a warm, bright windowsill for the winter.
- Harvesting. Pinch out shoot tips often; the plant sprawls and roots at the nodes, and regular cutting keeps it bushy and leafy.
In frost-free, wet climates it can spread vigorously. See growing herbs indoors and propagating herbs.