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Rice Paddy Herb (Limnophila aromatica [Lomk.] Merril)


botanicalLimnophila chinensis var. aromatica
Bulgarian Ароматна лимнофила
Aromatna limnofila
水芙蓉 [séui fuh yùhng], 田香草 [tìhn hēung chóu], 紫蘇草 [jí sōu chóu], 水花 [séui fā]
Seui fuh yuhng, Tihn heung chou, Ji sou chou, Seui fa
水芙蓉 [shuǐ fú róng], 田香草 [tián xiāng cǎo], 紫蘇草 [zǐ sū cǎo]
Shui fu rong, Tian xiang cao, Zi su cao
EnglishFinger grass
IndonesianDaun kerdemom, Selasih ayer kecil
Japaneseシソクサ, リモノフィラ
Shiso-kusa, Rimonofira
Korean소엽, 소엽풀
Soyeob, Soyop, Soyop-pul
Pak Khayaeng, Khayaeng
LithuanianKvapioji pelkenė
MalayBeremi, Kerak-kerak
PolishLimnofila pachnąca
RussianАмбулия ароматная
Ambuliya aromatnaya
Thaiผักแขยง, แขยง
Phak khayang, Kayang
VietnameseRau ngô, Rau om
Rau ngo, Rau om
Used plant part

Fresh leaves.

Limnophila aromatica: Rice paddy plant
Rice paddy plant (sterile shoots)
Limnophila aromatica: Rau om flower
Rice paddy herb flower
Plant family

Scrophulariaceae (figwort family, snapdragon family). According to some authorities, the genus Limnophila should be moved to the related plantain family (Plantaginaceae). Also, the order Scrophulariales is often included into its sibling order Lamiales.

Sensory quality

This herb has a unique flavour difficult to de­scribe. I feel it is def­initely lemony, with a certain tickling quality (see also lemon myrtle about citrus-scented herbs and spices). Some people like to describe it as sweet cumin or the air after a violent thunderstorm in summer or a sharp citrus odour; I have also read soapy, although I cannot agree.

Main constituents

The leaves contain about 0.1% essential oil, whose main component is limonene. Among the other compounds identified in the oil are perillaldehyde and an unusual monoterpenoid ketone, cis-4-caranone.


Several species of Limnophila are found in silent waters Southeast Asia; some of them are common aquarium plants in the West. In Vietnam, rice paddy herb is mostly cultivated in flooded rice fields.

A related species, Limnophila rugosa (Roth) Merril (syn. L. roxburghii, Herpestris rugosa Roth) has anise-scented leaves; it is used for culinary purposes only occasionally (Jawa).

Limnophila aromatica: Rau om greenhouse
Growing rice paddy herb
Limnophila aromatica: Kayang flowering tip
Rice paddy herb with flower

Because of its dependence on high tempera­tures and high air humidity, rice paddy herb culti­vation is a true chal­lenge out­side the tropics. I know of other­wise skilled gardeners who lost their plants regularly, but recently I have found a way that will (I hope) give me a constant supply of this great herb in the future. That’s how it goes: Get some fresh stems from another plant or your local Thai or Vietnamese grocer. If placed in water, they will de­velop roots within one or two weeks; in the mean­time, they must be cover­ed with a plastic bag or the like to give them enough air humid­ity. In this phase, direct sun­light will kill the plants, so put them in a shadowy but not dark place.
When enough roots have been formed, plant the stems into a high, trans­parent con­tainer filled with soil to cover most of the roots. A mixture of ordinary soil plus small, porous grains of burned clay is perfect. Keep the plants warm and humid. After a few days, they will tolerate (and even appreciate) intensive sunlight.


The genus name Limno­phila is formed from Greek limne [λίμνη] pond and philos [φιλός] friend and refers to the plant’s natural habitat. Some Chinese names also hint at the aquatic environ­ment: Mandarin shui fu rong [水芙蓉] water-hibiscus and Cantonese seui fa [水花] water flower. While other members of the genus grow only submersed, L. aromatica thrives above the water surface.

English rice paddy herb also hints at the growth of that plant in flooded rice fields. The English term paddy specifically means wet rice field, not just any area where rice is grown (derived from Malay padi uncooked rice). Cf. also Chinese tian xiang cao [田香草] fragrant field plant (the glyph for tian obviously shows fields from a bird’s perspective).

For reasons which I am unable to explain, there are extremely close ties between the names of rice paddy herb and perilla in several East Asian languages, even to the point of identical naming: Chinese zi su [紫蘇], Korean soyop [소엽] and Japanese shiso [シソク] usually stand for perilla, although they can mean rice paddy herb on occasion (especially in Korean). Yet, if any of these names is expanded by an element meaning grass, herb, it comes to mean rice paddy herb predominantly (zi su cao [紫蘇草], soyop-pul [소엽풀], shiso-kusa [シソクサ]).

Selected Links

Recipe: Cari ga [ca ri gà] ( Recipe: Vietnamese Chicken Curry [cari gà] ( Recipe: Cambodian Fish Soup (Samlor Machu Trey [សម្លម្ជូរត្រី]) ( Recipe: Vietnamese Fish Soup (Canh Chua) ( Recipe: Vietnamese Fish Soup (Canh Ca Nau Dua) ( Recipe: Vietnamese vegetable sour soup [Canh Chua] (

Limnophila aromatica: Rice paddy herb flowers
Rice paddy herb, flowering plant

Rice paddy herb is one of the many culinary herbs used only or pre­dominantly in Viet­namese cuisine; other examples include chameleon herb, Viet­namese coriander and long coriander. Yet the flavour of rice paddy herb is as much unique as it is pleasant, and the plant deserves wider recognition and usage; in reality, however, is appears quite rarely in Cambodian and Thai recipes, and nowhere else.

The intense, almost sparkling lemon odour of this plant harmonizes almost perfectly with fresh water fish. In the South of Vietnam, it is mandatory for spicy (sweet–sour–hot) fish soups (canh chua [canh chua]); the herb is not cooked, but served raw and coarsely chopped as part of the herb garnish that makes any South Vietnamese food really South Vietnamese. Canh chua is basically a milder version of the fiery Thai soup, tom yam (which, however, is more often prepared not with fish but with shrimps, see kaffir lime), but it acquires a unique character by the addition of fresh pineapple. In Cambodia, an almost identical soup is called Samlor Machu Trey [សម្លម្ជូរត្រី]. The spicy and fruity character of that soup is perfectly complemented by rice paddy herb.

Rich soups of that kind are commonly eaten as a full meal in South East Asia. In Vietnam, they are typically served not with rice but with fresh French white bread (baguette); often, a large pot of soup pot is placed in the center of the table and each diner dips the bread into the soup, similar to Swiss fondue.

The flavour of rice paddy herb goes particularly well with mild Vietnamese curries, e. g., chicken curry (ca ri ga [ca ri gà]). As their Thai counterparts, Vietnamese curries are based on coconut milk, but they are only lightly flavoured with a dash of chile, lemon grass and, as a French heritage, curry powder (see curry leaves). The intensive red–orange colour often comes from annatto oil. If rice paddy herb is not available, lemon- or anise-flavoured basil or simply coriander leaves make good alternatives.

Unfortunately, most Vietnamese cookbooks will omit this plant since it is not easily available outside of South East Asia. Most cookbooks silently supplant any reference to rice paddy herb by suggestions of other herbs popular in the region (basil, mint Vietnamese coriander and regular coriander).

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