Watercress (Xi Yang Cai): The Cooling Lung-Clearing Green

Watercress has one of the strangest biographies of any vegetable on a Chinese table. In the West it is a garnish, a peppery handful tucked under a steak or folded into a sandwich. In southern China — and above all in Cantonese home cooking — it is a soup vegetable: bought by the armful, simmered for two hours with pork bone, and served as the household's answer to a dry throat, a summer fever, or a cough that will not settle.

Its Chinese name tells the story. Watercress is xi yang cai (西洋菜) — literally "Western vegetable" — yet it has been fully absorbed into Chinese food therapy, where it is understood as a cooling, slightly bitter green that clears heat from the lungs and drains dampness downward. This guide looks at how TCM reads the plant, what it is traditionally used for, and how to cook it the way a Cantonese kitchen does.

What Is Xi Yang Cai?

Watercress is an aquatic brassica — a cruciferous vegetable, a relative of mustard, cabbage, and rocket — that grows in shallow running water. In Chinese markets it appears under two names. Xi yang cai (西洋菜) is the everyday Cantonese and market name, used for the soup green sold in thick bundles with hollow stems and dark green leaves. Dou ban cai (豆瓣菜) is the more botanical term you will see in herbals and agricultural texts.

Nutritionally it is one of the most concentrated leafy greens available: high in vitamin K, vitamin C, beta-carotene, calcium, and iron, and one of the richest dietary sources of glucosinolates, the pungent sulphur compounds that give it its peppery bite. That modern profile lines up neatly with the traditional description — a green that cools, moistens, and clears.

One practical note before we go further: in Chinese food therapy watercress is almost always cooked. The cooling nature is tamed by heat and by pairing, and cooking also removes the food-safety worry that comes with vegetables grown in water.

TCM Properties of Watercress

Every ingredient in Chinese food therapy is described by its thermal nature, its flavour, and the organ channels it enters. Watercress is a textbook cooling green:

• Nature (性): Cool — some texts list it as cold where it is used more aggressively for heat
• Flavour (味): Sweet and slightly bitter
• Channels (归经): Lung and Bladder
• Direction (趋向): Cooling, moistening, and draining — traditionally said to clear heat and promote urination

The flavour pairing is the key to reading this ingredient. The sweet flavour is nourishing and moistening; the slight bitterness is what "drains" and "clears." In the five-flavour framework, bitter is associated with the heart and with descending, drying action — it is the flavour that pulls heat downward and out. That is why watercress is traditionally described as clearing lung heat and easing coughs, and why it appears in the same family of recommendations as bitter melon and lotus seed.

The Lung channel is where most of the traditional action is said to take place. In TCM the lung is the "delicate organ" — it governs the breath, the skin, and the body's moisture, and it is the first organ to be affected by dry air, heat, and wind. A cooling, moistening green that enters the lung is therefore the traditional food for the throat that feels raw, the cough that comes with dryness, and the sensation of heat in the chest. The Bladder channel adds a second, complementary action: draining. Watercress is traditionally understood to move fluids downward and out, which is why it is recommended in warm, humid weather and when the body feels heavy and puffy.

Traditional Uses in Chinese Medicine

Watercress is not a tonic. It is a clearing, moving food, and its traditional uses cluster around heat and dampness rather than depletion.

Clearing Lung Heat and Easing Cough

This is watercress's signature use in southern China. When a cough is dry or productive with thick yellow phlegm, when the throat feels hot and scratchy, and when the voice is hoarse, TCM reads the pattern as heat in the lung. Cool, slightly bitter, moistening greens are the traditional dietary response. Watercress soup is what a Cantonese grandmother makes in exactly this situation — often with a sweetener such as honey dates to make it palatable, and sometimes with additional moistening ingredients such as white fungus. For a simpler, tea-based approach, a cooling infusion such as chrysanthemum tea works on the same principle.

Moistening a Dry Throat and Supporting the Voice

Autumn and the dry months of winter are, in TCM, the season of the lung, and dryness is its characteristic imbalance: a tickling throat, a dry nose, cracked lips, skin that feels parched, and a voice that tires easily. Because watercress is both cooling and moistening, it is traditionally recommended to offset dry heat — the kind that comes from heated indoor air, long hours of talking, or spicy food. It is often paired with ingredients that reinforce the moistening action, such as white fungus, lotus seed, or jujube dates.

Draining Dampness and Supporting Urination

The bitter flavour and the Bladder channel entry give watercress a second traditional role: draining. Where the body retains fluid — swollen ankles in humid weather, a heavy, sluggish feeling, scanty urine — TCM traditionally turns to mildly diuretic greens. Watercress is one of them, alongside adzuki bean, daikon, and mung bean. This is a gentle, food-level action rather than a therapeutic one, and it fits naturally into a summer cooling routine.

Cooling Summer Heat and Clearing the Skin

In Cantonese homes watercress soup is a hot-weather dish, eaten when the days are humid and the body feels "steamy." The traditional reasoning is straightforward: a cooling, draining green helps move heat out through the urine and the pores. Skin that flares in the heat — small heat rashes, prickly heat, or a complexion that looks flushed and oily — is read in TCM as heat rising to the surface, and cooling greens are the traditional dietary adjustment. BrothCalm's guide to foods for skin health covers the wider pattern.

Supporting Recovery and Light Meals

Watercress is also appreciated simply as a light, cleansing vegetable for people who have eaten heavily or who feel congested after rich food. It is a traditional accompaniment to fatty cuts — which is exactly why it is simmered with pork bone rather than eaten alone — and a pleasant way to add volume and bitterness to a meal without heaviness.

Watercress in the Kitchen

In Chinese cooking watercress is treated as a soup vegetable first and a stir-fry vegetable second. Both approaches are quick to learn.

Choosing and Storing

Look for bunches with crisp, hollow stems that snap rather than bend, and deep green leaves without yellowing or slime. Smaller, thinner stems are younger and less fibrous. Store watercress in the refrigerator wrapped in a damp cloth or in a loosely closed bag, and use it within two to three days — it wilts quickly. Wash it thoroughly in several changes of water, since grit clings to the stems.

Watercress and Pork Bone Soup (Xi Yang Cai Zhu Gu Tang)

The classic Cantonese preparation, and the one most often made at home.

• You will need: 500 g pork bone or pork neck, blanched · 1 large bunch watercress (about 500 g), washed and trimmed · 6 to 8 honey dates (jujube dates) · 3 slices fresh ginger · 2.5 litres water · salt to taste
• Method: Blanch the pork bones in boiling water for 3 minutes, then rinse. Bring 2.5 litres of fresh water to a boil with the bones, ginger, and honey dates, then reduce to a low simmer for 1 hour. Add the watercress and simmer for a further 45 to 60 minutes, until the stems are tender and the broth is deep green-gold. Season with salt and serve the greens alongside the broth.
• Why it works: The honey dates and ginger are not decoration. The dates add a gentle sweetness that both improves the flavour and, in TCM terms, moderates the cooling effect; the ginger warms the digestion so that a cooling green can be eaten comfortably.

Watercress with Honey Dates (Quick Version)

A lighter, faster soup for a weeknight or for one or two people.

• You will need: 1 bunch watercress · 4 honey dates · 2 slices ginger · 1.2 litres water or light vegetable stock · a pinch of salt
• Method: Simmer the dates and ginger in the water for 15 minutes. Add the watercress and cook for 10 to 15 minutes, until just tender. Do not overcook — long boiling dulls the peppery flavour and turns the greens grey.
• When to drink: As a light evening soup in warm weather, or when your throat feels dry and scratchy.

Garlic Stir-Fried Watercress

For a fast side dish that keeps more of the peppery bite.

• You will need: 1 bunch watercress, cut into 5 cm lengths · 3 cloves garlic, sliced · 1 tablespoon neutral oil · a splash of Shaoxing wine · salt
• Method: Heat the oil over high heat and fry the garlic for 20 seconds until fragrant but not browned. Add the stems first, toss for 30 seconds, then add the leaves. Splash in the wine, season with salt, and remove from the heat as soon as the leaves wilt — about one minute in total.
• Balance note: If you are eating watercress for its cooling properties in cool weather, add extra ginger or a pinch of white pepper to the pan, in line with the traditional principle of balancing a cooling food with a warming one.

Classic Pairings

• With pork bone or pork neck — the standard Cantonese combination, a rich base that balances the light green.
• With honey dates — sweetness softens the bitterness and moderates the cooling nature.
• With ginger — protects the digestion when eating a cooling vegetable.
• With dried duck gizzard (chen shen) — a traditional southern pairing for a throat that feels dry and a cough that lingers.
• With white fungus or lotus seed — for a more strongly moistening, lung-focused soup.

Cautions and Who Should Be Careful

Watercress is a food, not a medicine, and for most people it is a welcome addition to the table. A few traditional cautions are worth knowing.

• Cold or weak digestion: Because watercress is cooling, people who are traditionally described as having cold-deficient digestion — those who feel cold easily, have a poor appetite, bloat after meals, or pass frequent loose stools — are usually advised to eat it in smaller amounts, to cook it thoroughly, and to pair it with ginger, garlic, or pepper. This follows the general principle described in BrothCalm's guide to food energetics.
• Raw watercress: Watercress grows in water, and watercress from streams or ponds can carry liver fluke and other parasites if it is not washed and cooked properly. In Chinese food therapy it is virtually always cooked. If you enjoy it raw in salads, buy commercially grown watercress from a reliable source, wash it very thoroughly, and eat it fresh.
• Vitamin K and blood-thinning medication: Watercress is exceptionally high in vitamin K. Anyone taking warfarin or a similar anticoagulant should keep their intake steady rather than swinging between none and a large bowl, and should check with their healthcare provider.
• Pregnancy and nursing: Watercress has a long folk tradition of being limited during pregnancy because of its cooling, moving nature. This is a traditional caution rather than a confirmed risk. Because individual circumstances vary widely, ask your healthcare provider before making it a regular part of your diet.
• Kidney and thyroid considerations: Like other cruciferous greens, watercress contains goitrogenic compounds and oxalates. People managing thyroid conditions or a history of kidney stones may want to moderate very large, frequent servings and discuss it with a professional.

How Much, and When

There is no fixed dose in food therapy, only pattern and season. A practical approach:

• In warm, humid weather: One bowl of watercress soup two to four times a week, especially during the summer cooling season.
• In dry weather with a scratchy throat: A light watercress and honey date soup in the evening, two or three times a week.
• In cold weather: Less often, and always cooked with ginger, garlic, or pepper.
• If you have a cold constitution: Enjoy it occasionally as a side dish rather than as a regular soup, and lean on the warming soups and teas in the meantime.

Eaten this way — cooked, balanced, and matched to the season — watercress is one of the most useful greens in the Chinese food therapy repertoire: cooling where heat has gathered, moistening where dryness has settled, and draining what the body no longer needs.

Frequently Asked Questions

What is watercress called in Chinese medicine?

Watercress is known as xi yang cai (西洋菜), literally "Western vegetable," and also as dou ban cai (豆瓣菜). In Chinese food therapy it is classified as a cooling, slightly bitter green that enters the Lung and Bladder channels.

Is watercress cooling or warming in TCM?

Watercress is cooling (liang) in nature, with a sweet and slightly bitter flavour. It is traditionally used to clear heat, moisten dryness, and drain dampness, which is why it is most often eaten in warm weather or when signs of heat are present.

Can you drink watercress soup every day?

Watercress soup is traditionally enjoyed several times a week during hot or dry seasons rather than as a daily staple. Because the vegetable is cooling, people with a cold, weak digestion are usually advised to eat it in smaller amounts and to pair it with warming ingredients such as ginger.

Who should be careful with watercress?

People with cold-deficient digestion, frequent loose stools, or a weak constitution are traditionally advised to limit watercress. Watercress is also very high in vitamin K, so anyone taking blood-thinning medication should keep intake steady and speak with their healthcare provider first.

Is it safe to eat watercress raw?

Watercress is usually cooked in Chinese food therapy, both because cooking tames its cooling nature and because raw watercress from ponds and streams can carry parasites. Wash it thoroughly and cook it when you are unsure of its source.