Vietnamese coriander (Persicaria odorata) is a fascinating, unique little plant. It’s a cornerstone of Vietnamese cuisine, where it’s known as rau răm. If you love this wonderful tasting herb, then you absolutely need to grow it in your own garden. Read on to learn how!
You’re probably already familiar with regular coriander. Its seeds are round pods, kind of brownish, maybe a little stale because they’ve been sitting in their container at the back of your spice rack while you try to ignore their little reprimanding stares, daring you to try that festive Mexican antojito recipe you’ve been planning.
This is a totally different plant, from a totally different family.
While it shares a similar flavor profile with the leaves of what we know as the coriander plant (cilantro), Vietnamese coriander is unique.
It’s also known as “Vietnamese Mint” which should give you an idea of just how different this plant is from its Mexican namesake. Known as rau răm in Vietnam, Persicaria odorata leaves taste like a citrusy, peppery, more intense version of cilantro.
If you’re one of those people who can’t stand the smell or taste of cilantro, this herb probably isn’t for you. But on the other hand, maybe its spicy, lemony undertones will surprise you.
First off, let’s get to know this tender perennial. Vietnamese coriander is a tropical plant. It grows wild in frost-free zones with plenty of water, like Vietnam. If you’re in zone 11, you can plant rau răm in the garden and expect it to thrive. The rest of us should grow it in a pot and bring it inside before the nights turn cool.
There are three varieties of cilantro, all unrelated. They all have that unique, soap-like flavor, and they’re all tender, hot weather plants.
Cilantro (Coriandrum sativum)
Everyone’s favorite herb to accompany tacos and huevos rancheros. Cilantro—called coriander when it’s in seed form—hates to be transplanted. It’ll die when the weather dips below freezing, and will bolt if it’s stressed in any way. Transplant shock has caused countless gardeners to lose their cilantro plants early in the season.
Culantro (Eryngium foetidum)
Nearly identical to cilantro in every way, including its name. Culantro is actually an unrelated plant. It’s better able to handle transplanting than cilantro, though. Culantro also has a slightly stronger flavor than its standard counterpart.
Vietnamese Coriander (Persicaria odorata)
While it’s as tender and tropical as the other two cilantros, Vietnamese coriander handles transplanting and basic growing stressors better than the other two. It also grows wild like a weed in the right conditions. If you avoid cold, and give it plenty of water, rau răm can thrive in your garden easily!
What Does it Look Like?
Vietnamese coriander looks nothing like cilantro. In fact, it looks more similar to basil or mint. It belongs to the knotweed family of plants, which also includes buckwheat and rhubarb.
The leaves are long and slim with dark green tops and burgundy undersides. They’re often spotted with brownish-red patches. The stem is jointed where each leaf joins it, which is one of the characteristics shared by many of the knotweed family.
While this herb does flower in its native environment, it rarely flowers outside of the tropics. When it does flower, the blooms are small, whitish purple flowers. As a leafy, green houseplant, rau ram can thrive without flowering. It’s an easy plant to propagate by cutting.
Growing this Herb
Most people grow Vietnamese coriander from cuttings. In fact, it’s often easier to find a friend growing rau ram than it is to find seeds. It will rarely flower outside of ideal, tropical conditions, so gathering seeds can be a struggle.
Many gardeners who have successfully grown it for years have yet to produce any seed heads. If you ask around to seed companies, you may be surprised to find one or two that carry Vietnamese coriander seeds at over fifteen dollars a packet!
Fortunately, these plants are fairly easy to find, even if you don’t have a friendly Vietnamese grandmother living next door. Buy a couple of seedlings from a nursery and plant them in a pot them in moderate, well-drained soil. Give your seedlings a couple weeks to settle in, then start taking cuttings.
The seedlings are hardy enough to order through the mail, and many people will buy one or two young plants and then propagate their own plants.
Propagation from Cuttings
Simply snip a three-inch-long piece of stem with a few leaves attached from the mother plant. Vietnamese coriander rarely needs rooting hormone to propagate, but adding one of the natural rooting aids will help your cutting start rooting faster.
Set the cutting (with or without rooting hormone) in a glass of fresh, spring water. Let it sit in indirect sunlight for about a week, and watch for roots to start forming. When your cutting has a few, strong, little roots, plant it in some moist potting soil.
Keep these young cuttings moist, and out of harsh, direct sunlight for a few weeks as they adjust. Move your young plants into full sunlight after a few weeks, because this coriander is a sun-loving plant.
Caring for Vietnamese Coriander
You don’t need to pay much attention to your little plants after the first few weeks. Just keep them well watered and let them soak up the sunshine. Like most of the knotweed family, this is a self-sufficient plant.
Make sure you give your plants plenty of space. Full-sized Vietnamese coriander can grow up to 36 inches tall and bush out to over 15 inches. Don’t let its soil dry out! Many people plant this herb near ponds or wet areas so the soil can stay moist. On hot, sunny days, you might have to water in the morning and again at night.
Potted plants tend to dry out more quickly than in-ground plants. Since most people have to grow this herb in pots to save it from cold weather, you need to pay close attention to the soil.
Since it grows so quickly, you may need to repot your plant a few times during the growing season. If it looks like it’s stopped growing, it may just need a larger pot. Fortunately, as mentioned, it doesn’t mind being transplanted.
This herb grows best in moderate soil, so you only need to feed your plants occasionally. Twice a year, add a small amount of all-purpose fertilizer to your plants. More fertilizer will give you plenty of lush growth, but the essential oils in the plant will be diluted. That means you’ll have lots of leaves, but none of them will have much flavor.
When growing culinary herbs, it’s always best to under fertilize to preserve the plant’s flavor. After all, that’s the whole point of growing culinary herbs!
Many growers report no problems with pests at all. In fact, these spicy plants are unappealing to many invasive insects. Other gardeners say that their Vietnamese coriander can struggle with aphid invasions, especially while they’re spending the winter indoors.
If your plants are starting to show signs of aphid damage, spray them with short, direct spritzes of water daily to wash away the pests. If the aphids persist, use a gentle, insecticidal soap or an application of neem oil.
Harvesting Vietnamese Coriander
You can start harvesting Vietnamese Coriander leaves within a month of transplanting your cutting. This plant grows quickly. Young leaves are more tender and flavorful than older leaves. Some people say that older rau ram leaves have a tough, chewy texture and a slightly more bitter flavor. Others like to use the older leaves in stir fries and soups.
Just snip off a few, young leaves close to the stem to harvest. If your coriander plant is getting too large, or the older leaves are starting to take over, you can cut your plant back down to about five inches tall. Make sure to keep a few leaves and branches on the plant, and it’ll soon start growing a lot of fresh, young leaves.
Using the Leaves
Once you’ve harvested your leaves, what do you do with them? Obviously, this coriander is an essential ingredient in quite a few Vietnamese dishes. If you’re making spring rolls, curries, or pho soup, this little herb is an ideal addition. Otherwise, try adding it to spicy salsas, or throw it in a crab and cream cheese omelet for an amazing, unique brunch.
Using this herb may seem intimidating at first, because it’s not a common spice in American gardens. Fortunately, once you try it, you’ll soon look for ways to tuck it into everything. They’re even fantastic on salads. The leaves are also a traditional part of Vietnamese chicken salad—adding a spicy, citrusy flavor.
However you choose to use it in the kitchen, you’ll love the way this herb expands your culinary options and beautifies your herb garden.