Rice Paddy Herb

Common names

• Finger Grass
• Ng�
• Ng� Om
• Phak Kayang
• Rau Ohm
• Rice Paddy Herb

Rice paddy herb (scientific name Limnophila aromatica) is a tropical flowering plant. This herb is a member of the plantain family called Plantaginaceae. This herb is a smooth plant found growing in marshy and water-logged places in the tropics. The stems of rice paddy herb are simple, erect and stout and usually grow up to a height of anything between 30 cm and 60 cm. These plants seldom have aerial branches. The leaves of Limnophila aromatica or rice paddy herb are oblong-lanceolate or linear-oblong and grow up to a length of 2 cm to 6 cm and are generally 0.5 cm to 1 cm wide. They appear opposite to each other on the stem and are whorled. The leaves have a rounded clasping base, while the tip is pointed. The leaves of Limnophila aromatica have jagged margins. Rice paddy herb bears pink or light purple flowers which are borne solitarily or appear in whorls in inflorescences. The flowers appear at the leaf axils and have long and extremely thin pedicels that measure anything between 1 cm and 1.5 cm. The calyx is glandular, roughly 4 mm in length and divided into sections that are lanceolate. The corolla of Limnophila aromatica measures 1.2 cm in length, while the capsules are oblong shaped with pointed tips. Limnophila aromatica or rice paddy herb is also called Rau Ohm. This is basically a culinary herb having its origin in Southeast Asia, especially Vietnam. The flavour of rice paddy herb is akin to that of cumin, but it also has a tinge of citrus. This herb is most famously used in the Vietnamese cuisine called sour fish soup. Fresh rice paddy herb is extensively used in various types of soups and even curries in the form of an appealing and refreshing garnish. This herb needs moist soil and partial shade to thrive. In addition, this delicate plant should be protected from frost. Limnophila aromatica is an evergreen plant that likes to spread. Rice paddy herb has a preference for watery locales and you can easily cultivate this plant in shallow water, for instance the periphery of ponds where the water level is usually not higher than a few centimetres. Limnophila aromatica is popularly known as rice paddy herb and referred to as Rau Ohm in its native region in Vietnam. This species is variable depending on the region and climatic conditions where it is cultivated. Nevertheless, it is common is several regions of Southeast Asia. Rice paddy herb was relatively unknown outside the tropics, but now it is being gradually recognized for its increasing popularity in the form of an aquarium plant. This herb is spread all over the tropical as well as sub-tropical regions of Asia, in addition to the northern regions of Australia. This plant is found growing naturally in shallow water, such as swampy lands. In addition, this herb also grows as a weed in the inundated rice fields. People in Southeast Asia use Limnophila aromatica in the form of a spicy herb. In Vietnam, rice paddy herb is also used as a base for herbal infusion. Usually, rice paddy herb is cultivated in inundated fields. Limnophila aromatica is also available in Europe, especially in the form of a fresh herb in some Asian grocery shops. The characteristic flavour of this plant can be described as lively and spicy, which reminds one of curry, cumin or citrus. The scientific name of this herb suggests that the leaves of the herb have a somewhat aromatic scent, especially when they are crushed. The aroma of the leaves is attributed to the essential oils contained by them. Limonene is the main element present in the essential oil extracted from rice paddy herb.

Parts used

Leaves, roots.

Culinary uses

The aroma as well as flavour of Limnophila aromatica reminds one of both cumin and lemon. In Vietnamese cuisine it is used very often and is locally known as ng� om. Rice paddy herb forms an important ingredient in a sweet and sour seafood soup called canh chua, which also contains tamarind. However, ng� om should not be mistaken for ng� gai. The latter is added in the form of an accompaniment to ph?, a noodle soup prepared by the Vietnamese. In Thai cuisine, Limnophila aromatica is called phak kayang and is used to prepare om. Many people usually consume rice paddy herb raw or chop the herb and use it to garnish various Vietnamese dishes. The essence and flavour of Limnophila aromatica is best when it is served raw. Herbs like Limnophila aromatica are popular because of the special flavour they contribute to soups, fish and meat dishes. These herbs are also used in curries.

Habitat and cultivation

Limnophila aromatica or rice paddy herb is mainly cultivated in soggy environments such as flooded rice fields in regions having hot temperatures. This plant has its origin in Southeast Asian nations like China, Vietnam and India. Rice paddy herb was introduced into North America in the beginning of the 1970s. Rice paddy herb grows best in boggy or swampy soils, which is common in its native regions, such as those in the Southeast Asian nations. Moreover, this plant needs high air humidity and elevated temperatures to thrive. In case you are growing Limnophila aromatica in your aquarium, you should remember that light plays a vital role in the growth of this plant. It is advisable that you grow this plant in a rich damp loam substrate. Since the survival and growth of the rice paddy herb is heavily dependent on high air humidity and high temperatures, it is really challenging to cultivate this plant in areas outside the tropics. Generally, Limnophila aromatica is grown from cuttings. After cutting the stems, they are immediately placed in water. The stems will develop new roots in a very short period - just a couple of weeks from planting. During the rooting phase of rice paddy herb, it is advisable that you cover the plants using transparent plastic bags so that the plants get sufficient humidity. Subsequently, you can place the plants in a rather shadowy location, as sunlight can be critical for the plants at this stage.