Vietnamese Coriander - Persicaria odorata

Persicaria odorata, known as Rau ram in Asia, Vietnamese coriander or Vietnamese mint in English, is a creeping plant related to knotweeds and other Polygonum. Its aromatic vegetation, leaves and stems, is used in Asian cuisine. The flavour and aroma of the young leaves evoke both coriander and lemongrass when consumed raw, while cooked stems and leaves have a more peppery aroma that pairs well with meats. It is a tender perennial plant, which is most often grown as an annual in open ground. In the garden or in a pot, plant it after the last frost, in mid-May, for a spring to summer harvest as needed. You can keep it from one year to the next by overwintering it in a frost-free location. This aromatic knotweed, with its spreading habit, is also well-suited for hanging basket planting.

The Vietnamese coriander, scientifically known as Persicaria odorata, belongs to the family Polygonaceae, like our ornamental knotweeds. It is native to tropical and subtropical regions of Asia, particularly Vietnam. It is a perennial and aromatic herbaceous plant, capable of living several years in the garden if the temperature does not drop below -5°C (23°F) in winter. The aboveground parts are damaged as soon as it freezes, at 0°C (32°F). Its growth habit is more creeping than upright, reaching about 30cm (12in) in height and 50 to 60cm (20 to 24in) in width depending on growing conditions, and theoretically persists in winter, free from frost. The plant develops decorative foliage, composed of small lanceolate leaves speckled with a dark spot in the shape of a V towards the centre of the leaf. It blooms in summer, with pale pink spike-like flowers.

In cooking: Rau ram is mainly cultivated for its freshly picked young leaves. Used cooked or added at the last minute, they flavour meats such as pork, beef, chicken, and duck, as well as soups. Vietnamese coriander is an essential ingredient in traditional Vietnamese dishes such as shrimp fritters, spring rolls, and other dumplings.

Harvesting: Harvesting is done directly with scissors or by pinching as needed in cooking. This pruning stimulates the plant and promotes the formation of new shoots. It is useful to have your herbs within reach, in a pot on the windowsill or nearby in the garden, so you don't have to cross the entire vegetable garden every time you need them.

Storage: Rau ram is best consumed fresh, but it freezes very well. To do this, wash and let it dry thoroughly. Gather the leafy stems into bundles and place them in a freezer bag. You can then keep it all winter and use it as needed. Once dried, the plant loses much of its flavor.

Gardening tip: Mulch the soil in summer to maintain freshness and save on watering, as Chinese basil is a plant that prefers very moist to wet soil and does not tolerate drought or blazing sun. Mulching also helps limit the appearance of "weeds." Add compost at planting time, as the plant is nutrient-hungry.