The ‘laksa leaf plant’ is an exotic herb and a must-have ingredient in tangy Asian dishes, writes Elaine Yim
HAVE you heard of Vietnamese mint or Vietnamese cilantro? It is not commonly used in western dishes and is regarded as an exotic herb from Southeast Asia. It is said to be widely used in Vietnam as a substitute for peppermint and cilantro, the 3-in-1 with the fantastic flavour of coriander and mint, and the potent aroma of real lemons.
Malaysians call it the “laksa leaf” plant, named after our popular asam laksa dish. It is the secret to the tastiness of Penang asam laksa, ranked seventh by CNN Travel out of 50 most delicious food in the world. Home chefs will insist that we can’t make a good, tasty bowl of asam laksa without the laksa leaves or daun kesum. It is a must-have ingredient in our asam laksa, asam pedas, asam fish, tom yam seafood and Peranakan dishes. This plant can be grown in our home gardens.
Scientific name:Persicaria hydropiper
Synonym:Polygonum hydropiper, Persicaria odorata, Polygonum odoratum, Polygonum minus
Common names: Laksa Plant, Laksa Leaf, Vietnamese Mint/Coriander, Cambodian Mint, Hot Mint, Smartweed, Water Pepper, Marsh Pepper
Vernacular names: Daun Kesum, Daun Laksa (Malay), Rau Ram (Vietnam), Phak Phai (Thailand)
The genus Persicaria is made up of about 100 species of flowering plants from the Polygonum family of knotweeds and smartweeds, including herbs, shrubs, small trees and vines.
Polygonum is probably derived from the Greek word “poly” meaning many and “gonu” meaning knot or knee, referring to the stem structure with many nodes and joints. Persicaria is derived from the scientific name for peach, Prunus persica, as their leaves are quite similar in shape.
Hydropiper is derived from the Greek word “hydor” for water and “peperi” for pepper. This plant is adapted to live in aquatic environment and has an acrid peppery taste, hence its common name, the water pepper.
The plant is native to Southeast Asia where it grows wild in the cool highlands, and the warm and damp areas of the lowlands along the banks of streams, rivers, ponds and lakes. It is also found in other tropical, subtropical and temperate countries around the world.
Persica hydropiper is a creeping perennial herb that can grow to a small bush of about 50cm tall and 45cm wide. In the cooler highlands, it can reach a height of 1.5m tall. The stems are slender, cylindrical and light green in colour with a tinge of pink. There are numerous nodes at 1cm intervals along the stems which can root easily when it touches soil.
The leaves are about 5-7cm long and 2cm wide, lance-shaped, alternately arranged and dark green in colour with brown markings. The pinkish-white flowers are tiny and borne in racemes. All parts of the plant are fragrant.
CULINARY AND MEDICINAL USES
The fresh leaves of this edible herb is widely used in Southeast Asian cuisine, particularly spicy hot and sour dishes like asam laksa, asam fish and tom yam. The young leaf shoots can be eaten raw as ulam or kerabu.
The leaves contains antioxidants, minerals such as calcium, phosphorus, iron, sodium, potassium, magnesium, copper, zinc, and vitamins A, B1, B2, niacin and C. It is used as a traditional remedy for indigestion, dandruff and post-natal tonic.
HOW TO GROW
It is best planted in a container. You can place it outdoors or indoors near a bright kitchen window, use it in landscaping as a ground cover or as border plant near ponds, bogs and water gardens.
Propagation You can buy a potted young plant from nurseries specialising in local herbs. If the plant is big enough, separate it into two pots of plants. Another way is to take 15-20cm long stem cuttings with 5-7 nodes. Place the cuttings in a container of water for 1-2 weeks to root them before planting in soil. You can also use stem cuttings from store bought ones.
Sunlight Partial sun.
Medium Rich, moist but well drained soil is preferred.
Water Require lots of watering. Do not let the soil dry out.
Fertilise Compost, foliar spray or balanced compound fertiliser (NPK 15:15:15) once a fortnight.
Prune Pinch off the tips to encourage branching and bushiness.
Harvest It is a fast grower. You should be able to harvest the leaves in about one to two months’ time.
Pest and diseases. May be attacked by thrips and aphids.
Remember to water the plant as it is not drought-tolerant. Do not over-feed the plant with fertiliser as this will result in more leaves but reduced flavour and aroma.