How to Grow Vietnamese Coriander (Rau Ram): Care & Overwintering

Here’s the short answer: Vietnamese coriander (Persicaria odorata), known as rau ram, is a fast-spreading, heat-loving perennial herb that thrives in warmth, moisture, and sun to part shade, and unlike true cilantro it never bolts in summer heat. That makes it the perfect warm-season substitute for cilantro, delivering a similar citrusy flavor with a peppery, spicy kick straight through the hottest months. It roots almost effortlessly from cuttings and grows happily in a pot or a damp garden bed. The one catch is cold: rau ram is tender, hardy outdoors only in USDA zones 9 to 11, so in cooler climates you grow it in a container and overwinter it indoors. Give it heat, plenty of water, and protection from frost, and a single plant will supply leaves for years.

What Is Vietnamese Coriander?

Vietnamese coriander, called rau ram in Vietnam and also known as Vietnamese mint or hot mint, is a low, sprawling perennial herb in the knotweed family (Polygonaceae). Despite its English name, it is not related to true coriander (cilantro) or to mint. It grows as a creeping, jointed-stemmed plant about 6 to 15 inches tall, with narrow, pointed green leaves often marked by a dark maroon chevron. Crush a leaf and you get a bright, citrusy, cilantro-like aroma followed by a distinctly peppery, spicy heat that lingers on the tongue.

In Southeast Asian cooking it is indispensable, eaten raw in fresh spring rolls and salads, scattered over noodle soups like pho, paired with the classic Vietnamese egg dish, and served with the famous Vietnamese fertilized-egg snack. It also turns up in laksa in Malaysia and Singapore, where it is known as laksa leaf, and it pairs especially well with seafood, chicken, and tangy, lime-dressed salads. Because its flavor closely echoes cilantro but holds up in heat, gardeners in hot climates often grow it specifically as a cilantro stand-in for the summer months, when true cilantro bolts within weeks.

Light, Climate, and Hardiness

Sun and temperature

Rau ram is a tropical plant that revels in heat and humidity. It grows best in full sun in cooler climates but appreciates afternoon shade where summers are hot, since intense, dry sun can scorch and toughen the leaves. A spot with morning sun and dappled afternoon light keeps the foliage tender and abundant. Growth is fastest when temperatures stay between 70 and 90°F; the plant slows markedly as things cool and stops growing below about 50°F.

Cold hardiness

This is the one limitation to plan around. Vietnamese coriander is reliably perennial outdoors only in USDA zones 9 to 11. It is damaged by frost and killed by a hard freeze. In zones 8 and warmer it may die back to the ground in a mild winter and resprout in spring, but in zones 7 and colder it will not survive the winter outdoors. The practical solution everywhere with frost is to grow it in a container so you can move it indoors, which is easy since it stays compact and roots so readily.

Soil, Water, and Planting

Coming from wet tropical ground, rau ram is one of the few culinary herbs that genuinely loves moisture. Give it a rich, consistently damp soil; it will not tolerate drying out for long and wilts quickly when thirsty. It even thrives in boggy spots, at pond margins, or standing in a saucer of water, conditions that would rot most herbs. In a container, use a moisture-retentive potting mix and be prepared to water frequently, especially in summer heat. A slightly acidic to neutral pH suits it fine.

The easiest way to start is from a cutting or a nursery plant rather than seed, as seed is hard to find and germination is unreliable. Set plants or rooted cuttings about 12 inches apart; they spread quickly by creeping, rooting stems and will fill a bed or pot within a season. Because it spreads aggressively, many gardeners prefer to keep it contained in a pot, which also makes overwintering simple.

Propagating from cuttings

Few herbs are easier to multiply. Snip a 4- to 6-inch stem, strip the lower leaves, and stand it in a glass of water on a windowsill; roots appear within a few days to a week. Pot the rooted cutting up in moist soil and it takes off. You can also lay a stem on damp soil and it will root at the joints on its own. This makes it trivial to keep a backup plant indoors, share with friends, or replace a winter-killed plant in spring.

Ongoing Care

Beyond keeping it watered, rau ram needs little. Feed container plants every three to four weeks during the growing season with a balanced liquid fertilizer to support continual leaf production; garden plants in rich soil may need none. Pinch or harvest regularly to keep the plant bushy and prevent it from getting straggly. If stems grow long and leggy, simply cut them back hard, the plant rebounds quickly and you can root the trimmings. Tiny pinkish flowers may appear in summer but, importantly, the plant keeps producing good leaves regardless, with none of the flavor collapse that bolting causes in cilantro.

Pests are few. In the humid conditions it likes, watch for the occasional aphid or for slugs and snails on damp ground; spider mites can appear on indoor plants in dry winter air. Good airflow and avoiding stagnant, soggy crowns help prevent rot. If you grow rau ram in a pot, repot it into fresh soil each spring, as the vigorous, spreading roots quickly exhaust a container, and divide overgrown clumps at the same time to rejuvenate tired plants and make more of them.

Overwintering Vietnamese Coriander

In zones colder than 9, overwintering indoors is the way to keep your plant going year after year. Before the first frost, bring the container inside (or take cuttings and root them for a fresh, compact indoor plant). Set it in a warm room at your brightest window, ideally with a grow light, since rau ram dislikes both cold and low light. Keep the soil moist but reduce feeding, and accept that growth will slow over winter and the plant may look a bit thin. Watch for spider mites in dry indoor air and mist occasionally to raise humidity.

If you lack good indoor light, the simplest insurance is to root several cuttings in fall so you have small plants to carry through to spring. Once the weather warms reliably and all frost danger has passed, harden the plant off and move it back outside. For more strategies on protecting tender plants through the cold, see our guide to bringing houseplants inside for winter.

Harvesting and Using Rau Ram

Harvest by pinching off the top few inches of stems with their tender young leaves, which encourages bushier regrowth. The youngest leaves are the most aromatic and least fibrous. Use rau ram fresh and raw whenever possible, since its flavor fades with cooking and storage; add it at the end of a dish or serve it as a fresh garnish. Stems keep for a few days standing in a glass of water on the counter, like cut flowers, or wrapped in a damp towel in the fridge. With its bolt-proof habit and easy propagation, a single plant can keep your kitchen in cilantro-like flavor all summer and beyond. For other warm-climate and container herbs, browse our Plants & Flowers hub, and if your foliage is yellowing, our guide on why herb leaves turn yellow can help you diagnose the cause.