From a windowsill to a farm dam, this essential herb in Vietnamese cooking can be grown by almost anyone! In colder climates, try overwintering it indoors in a warm, bright spot, while in tropical conditions, it can thrive in wet soils and even colonise a rice paddy. Rau om is also used in Ayurvedic and other traditional medicine systems.

Rau Om: Culinary Uses and Traditional Medicinal Benefits

Rau om (Limnophila aromatica), also known as rice paddy herb, is an important ingredient in Vietnamese sour fish soup and is used in Cambodian and Thai cooking. Its distinctive citrusy, cumin-like flavour pairs particularly well with fish, seafood, tamarind and spicy soups. Mainly used fresh – grow it for the real  Southeast Asian taste!

In traditional medicine across Southeast Asia, Limnophila aromatica has been used for digestive complaints, fever and respiratory congestion. Traditional preparations include leaf decoctions and fresh plant juice, while the leaves have also been applied to wounds in some regional medicinal traditions. 

How to Grow Rice Paddy Herb

Native to tropical and subtropical Asia, rice paddy herb thrives in warm, humid conditions around wetlands, shallow ponds and rice fields. It will happily spread when conditions are favourable. As a semi-aquatic plant, it can grow in shallow water or fertile, consistently moist soil; however, an ordinary, well-drained garden bed is likely to be too dry.

Provide full sun to partial shade, with plenty of water and soil that never dries out completely. Humid air is beneficial, particularly in hot weather, but maintaining moisture around the roots is essential. Given warmth and ample water, the plant can spread vigorously, making a pond edge, bog garden or water-holding container ideal growing locations.

Cold Hardiness and Overwintering

Rice paddy herb is a warmth-loving tropical plant that is sensitive not only to frost but also to prolonged cold. Growth slows considerably in cool weather, and temperatures around 10°C or below may cause serious damage, particularly with prolonged exposure. At around 5°C, the plant is at high risk of severe damage or death, even without frost. In climates with cold winters, grow it in a pot that can be moved indoors well before temperatures drop, providing a warm, bright position and a consistently moist growing medium.

It would look really nice in a fish bowl (just the herb, no fish necessary!)