Roots and rhizomesDampness-drainingPolygoni Cuspidati Rhizoma et Radix

Hu Zhang (Giant Knotweed Root)

Q: What are the composition and effects of Huzhang?

Huzhang is slightly bitter and slightly cold, enters the Liver, Gallbladder, and Lung meridians, and functions to drain dampness and clear jaundice, clear heat and detoxify, disperse stasis and relieve pain, and stop cough and transform phlegm. It is used for damp-heat jaundice, turbid strangury, leukorrhea, wind-damp bi pain, abscesses and sores, burns and scalds, amenorrhea, abdominal masses, traumatic injuries, and lung heat cough.

Q: How to choose between raw and processed? Can Yinchen replace it?

The rhizome is used raw. Yinchen emphasizes jaundice rather than strongly dispersing stasis, so it cannot replace Huzhang in equal amounts. Commercial products are standardized, so do not adjust arbitrarily.

Q: What is the dosage of Huzhang? Can it be used daily as a jaundice-clearing tea?

The decoction dose is 9-15 g, but modern use requires physician-determined dosage. It is not a year-round Huzhang tea. Prolonged use can further injure pregnancy, and jaundice use should be short-term and physician-guided rather than a substitute for evaluation.

Q: What are the contraindications of Huzhang? Can pregnant women use it?

Use with caution in pregnancy. Stop if loose stools or abdominal pain occur, and seek immediate medical care for severe jaundice or high fever.

Q: Can Huzhang clear jaundice, detoxify, and disperse stasis?

It can help with damp-heat jaundice, turbid strangury, leukorrhea, wind-damp bi pain, abscesses and sores, burns and scalds, amenorrhea, abdominal masses, traumatic injuries, and lung heat cough. It drains dampness and clears jaundice, clears heat and detoxifies, disperses stasis and relieves pain, and stops cough and transforms phlegm, but it is not a specific remedy for all jaundice or all cough.

Q: Can Huzhang be taken daily as a jaundice-clearing or stasis-dispersing tea?

Damp-heat jaundice use is short-term and formula-based; pregnancy can be further injured. The idea that Huzhang must clear jaundice cannot replace evaluation, and draining dampness and dispersing stasis require physician-determined formulation and dosage.

A practical guide to Hu Zhang: what it is, how Traditional Chinese Medicine uses it, the classical formulas it appears in, and who should be careful with it.

View Herb Profile →

Last reviewed Oct 28, 2026

Quick Facts

Latin Name	Polygoni Cuspidati Rhizoma et Radix
Chinese Name & Pinyin	虎杖 · Hu Zhang
Medicinal Part	Roots and rhizomes
The item	Hu Zhang is the dried root and root-stem of Japanese knotweed. Salvia (Dan Shen) and sheep's sorrel root (Yang Ti) are not this herb. It goes into a standard decoction.
Nature and channels	Bitter, slightly cold. Enters the Liver, Gallbladder, and Lung. Bitter slightly cold clears damp-heat and disperses stasis to stop pain.
Pharmacopoeia line	Clears and drains damp-heat. Dispels stasis and stops pain. Used for damp-heat jaundice, damp-heat diarrhea, blood-stasis joint pain, bruising injury, and retained lochia.
Pattern cues	Damp-heat jaundice. Damp-heat diarrhea. Fixed aching joint pain. Bruising injury.
In this article	Hu Zhang versus Dan Shen and Yang Ti. Clearing damp-heat versus moving blood. Why the dose is 9–15 g. Why pregnancy and heavy menses are cautions. Why jaundice and lochia need a clinic. Who should skip it.

What Is Hu Zhang?

Hu Zhang (虎杖; Hǔ Zhàng; Latin: Polygonum cuspidatum; English: Japanese knotweed) is the dried root and root-stem of a perennial buckwheat-family plant, dug mainly in autumn to winter, washed, sliced, and dried; the raw form is common, with stir-fried or wine-processed versions also available. It is bitter and slightly cold, enters the Liver, Gallbladder, and Lung channels, and its core actions are to clear and drain damp-heat, and to disperse stasis and stop pain. It goes into a standard decoction and needs no special pre-decocting or late addition. The usual amount is 9–15 g.

It is not Dan Shen. Salvia is slightly cold, bitter with a touch of sweet, mainly moving and nourishing blood, regulating menses, and settling the mind; it does not clear damp-heat as Hu Zhang does. It is not Yang Ti. Sheep's sorrel root is more yellow on the surface, lighter on the cut face, and sour — a different Polygonaceae look-alike. Use caution in pregnancy and nursing. People with heavy menstrual flow should not self-use. People with cold, weak digestion — stomach pain, loose stools, cold hands and feet — should not self-use. Blood deficiency without stasis is a poor match.

It is used most often for three patterns:

Damp-heat jaundice, damp-heat diarrhea — yellowing skin or eyes, sticky stools, bitter mouth, greasy yellow coating — seek care
Blood-stasis joint pain and bruising injury — fixed sharp pain, local swelling, bruises
Retained lochia after childbirth and abdominal masses — seek care

Bitter and slightly cold, it is not a daily "clearing knotweed" to keep increasing. Draining when there is no damp-heat, or moving blood when there is no stasis, injures Spleen yang and consumes qi and blood.

When damp-heat piles up in the Liver and Gallbladder, or blood stasis blocks the joints and channels, yellowing, sticky stools, bitter mouth, and fixed aching pain are common. Hu Zhang is bitter and slightly cold. It clears damp-heat and disperses stasis, which is why it appears in Yin Chen Hu Zhang Tang–type formulas for damp-heat jaundice, and in Hu Zhang San–type formulas for bruising and joint pain. It drains more than it nourishes. A cold weak stomach, with no damp-heat, gets worse if more is added.

Hu Zhang is not a catch-all damp-heat or pain root. In cold, weak digestion, blood deficiency without stasis, or pregnancy, using it alone is a poor match. Whether it belongs in a formula, and at what dose, should be decided by a licensed Chinese medicine practitioner after pattern diagnosis.

Hu Zhang: Materia Medica Profile

Identification & Quality Standard

Polygoni Cuspidati Rhizoma et Radix

Botanical Origin

The dried root and rhizome of Polygonum cuspidatum Sieb. et Zucc.(Polygonaceae)

Production Regions

Primarily produced in the Chinese provinces of Jiangsu, Zhejiang, Guangdong, Anhui.

Quality Requirements

Superior medicinal material is thick and strong, with firm and yellow fractured surface.

Macroscopic Features

Often cylindrical short sections or irregular thick pieces, 1~7cm long, 0.5~2.5cm diameter. Outer skin is brown, with longitudinal wrinkles and rootlet scars, cut surface has relatively thin cortex, and wide xylem, brown, radial rays, cortex and xylem are easily separated. Pith of rhizome has a septum or hollow-shape. Hard texture, faint odor, slightly bitter and astringent taste.

Where It Grows and How to Judge Quality

Traditional sources and industry experience often pay attention to the Jiangsu, Zhejiang, and Anhui regions, though actual quality also depends on variety, harvest timing, processing, and storage.

Good-quality raw Hu Zhang usually looks like this:

Cylindrical, branched roots, with a brown surface and irregular longitudinal wrinkles.
Hard, with a thin bark, wide wood layer, and radial markings on the cut face.
Tastes slightly bitter and astringent.

The processed form is deeper in color with a slightly changed smell. Watch out for look-alikes from the same family, such as the root of Yang Ti, which is more yellow, lighter on the cut face, and more sour — easy to tell apart by look and smell.

Traditional Properties & Historical Lineage

Nature, Flavour & Channel Tropism

Bitter; Slightly coldLiverGallbladderLung

1. What the Classics Recorded

Hu Zhang has a clear paper trail in Chinese herbal literature. A few highlights:

Ming Yi Bie Lu — noted it could "promote menstrual flow and break stagnant blood masses."
Xin Xiu Ben Cao — recorded that boiling the juice was used for wind in the bones and blood stasis.
Ben Cao Gang Mu — added uses for retained lochia after childbirth, abdominal masses, bruising, summer heat, wine toxin, and snake bites.
De Pei Ben Cao — noted pairings: with Huang Lian for damp-heat diarrhea, and with Niu Xi for joint pain.

These records center on clearing damp-heat and easing stagnant-blood pain — they do not equal modern medical conclusions.

2. How Views of the Herb Changed Over Time

Different generations of physicians read Hu Zhang a little differently. Some early practitioners stressed its blood-moving side, using it for gynecological blood-stasis patterns. Later physicians discovered its damp-heat-clearing role and used it for jaundice and damp-heat diarrhea. Others emphasized that its nature is slightly cold, so people with cold, weak digestion should use it with care — and that it should not be treated as a tonic or used for just any pain. These differences helped define its proper scope.

This evolution is a good reminder of a core idea in traditional Chinese medicine: herbs are chosen to match the person, not just the symptom.

Core Efficacies & Traditional Applications

Traditional Functions

Drains dampness and reduces jaundice, clears heat and resolves toxin, dispels stasis and stops pain, resolves phlegm and stops cough.

1. Main Use One: Clearing Damp-Heat

What it is: The first core use of Hu Zhang is to clear damp-heat.

When it was used: Traditionally for damp-heat jaundice and damp-heat diarrhea — yellowing of the skin or eyes, sticky, uncomfortable stools, a bitter dry mouth, and a greasy yellow tongue coating.

Common partners: Often paired with damp-heat herbs such as Yin Chen or Zhi Zi. For damp-heat diarrhea, Huang Lian or Mu Xiang may be added.

Who should not self-use: People with cold, weak digestion — frequent stomach pain, loose stools, cold hands and feet — should avoid it on their own, since it could worsen the cold.

2. Main Use Two: Easing Pain from Stagnant Blood

What it is: The second core use focuses on easing pain from stagnant blood.

When it was used: Traditionally for joint pain and bruising from blood stasis — a sharp, fixed pain, local swelling and pain after injury, and bruises under the skin.

Common partners: Often paired with blood-moving, pain-easing herbs such as Hong Hua, Tao Ren, or Niu Xi. For injury, Ru Xiang or Mo Yao may be added.

Who should not self-use: Pregnant women and people with heavy menstrual flow should avoid it on their own, to keep from disturbing qi and blood.

3. A Classic Pairing: Hu Zhang and Yin Chen

A common pairing is Hu Zhang with Yin Chen. Hu Zhang is good at clearing liver-gallbladder damp-heat, while Yin Chen is good at draining dampness and easing yellowing. Together they strengthen the liver-gallbladder damp-heat-clearing effect, helping with jaundice and dark urine.

Like most pairings, this one should be matched to the person, not copied from a list. It belongs in the hands of a practitioner.

Modern Research

Modern research offers useful context, but Traditional Chinese Medicine prescribes on whole-pattern diagnosis rather than isolated compounds.

1. Main Chemical Compounds

Modern studies have detected several groups of compounds in Hu Zhang:

Anthraquinones — the main group, including emodin, chrysophanol, and rhein.
Stilbenes
Flavonoids
Polysaccharides and tannins

One important point: detecting a compound in a plant does not mean that compound produces the same effect in the human body. Lab chemistry and human response are two different things.

2. Where Research Is Heading

Research so far is mostly at the early laboratory stage. What has been observed:

In test-tube experiments, some anthraquinone components showed activity against certain bacteria.
In animal studies, the extract showed a mild anti-inflammatory effect at certain doses, and some extracts showed a trend toward regulating blood-lipid levels.
Some components showed antioxidant activity in the test tube.

These are promising early findings, not proven human benefits. Human clinical research is still limited.

3. The Limits of Current Research

It is important to read the research honestly. Four limits stand out:

Lab results are not clinical results. Test-tube and animal findings cannot be carried straight into human use — the body's environment differs greatly from the lab.
Extracts are not the dried herb. Experiments often use separated single compounds or concentrated extracts, which differ from everyday dried slices in dose and action.
Doses and methods vary. Different studies use different solvents, concentrations, and delivery methods, so results are hard to unify.
One compound is not the whole herb. Hu Zhang's components are complex and may interact; a single one should not stand in for the whole herb.

Comparing Similar Herbs

1. What Hu Zhang and Dan Shen Share

Dan Shen is the herb Hu Zhang is most often compared with. They share quite a lot:

Both are traditionally used to ease pain from stagnant blood.
Both are used for qi-blood-flow patterns such as joint pain and bruising.
Both need attention to body type and dose — neither suits everyone long-term.

2. The Core Differences

Despite the similarities, the two herbs differ in a few practical ways:

Nature: both are slightly cold and bitter. Hu Zhang is bitter, with clearing damp-heat as its main role. Dan Shen is bitter with a touch of sweet, mainly moving blood and nourishing blood.
Focus: Hu Zhang's core strength is clearing damp-heat while also moving blood — suited to damp-heat mixed with stasis. Dan Shen's core strength is moving blood, regulating menses, and settling the mind — suited to stasis with an unsettled heart or irregular periods.
Direction of action: Hu Zhang leans toward draining and clearing — clearing damp-heat and opening blood stasis. Dan Shen leans toward moving and passing — moving blood and opening the menses, with some blood-nourishing so it does not overly drain qi and blood.
Best fit: Hu Zhang suits damp-heat jaundice, damp-heat diarrhea, and achy swollen joints with a bitter taste and greasy coating. Dan Shen suits irregular periods, blocked painful menses, an unsettled mind, poor sleep, and bruising with blood deficiency.
Caution: Hu Zhang is avoided for cold, weak digestion without damp-heat, and pregnant women should be cautious. Dan Shen is avoided for heavy menses or those without blood stasis; pregnant women should also be cautious. Because Dan Shen also nourishes blood, it can be used in some qi-blood-deficient states, whereas Hu Zhang does not suit those.

3. The Difference in One Sentence

Hu Zhang leans more toward clearing damp-heat while easing stagnant-blood pain, while Dan Shen leans toward moving and nourishing blood, regulating menses, and settling the mind. Both can be used for stagnant-blood pain, but they are not freely interchangeable.

Classical Formulas Containing Hu Zhang

Formula One: Hu Zhang San

How it is built: In this formula, Hu Zhang is the main herb (sovereign), leading the stagnant-blood pain-easing role. It is typically paired with blood-moving herbs such as Dang Gui and Hong Hua to open blood stasis, and may include Niu Xi to guide the action downward and ease lower-limb joint pain. Using Hu Zhang alone is not enough — a single herb cannot cover the blood-moving, qi-moving, and pain-easing needs together.

Traditional use: This formula was used for bruising and joint pain from blood stasis — local swelling and pain, bruises, and a fixed, unchanging pain.

Modern note: Any modern use should go through proper assessment — do not self-apply based on the name.

Formula Two: Yin Chen Hu Zhang Tang

How it is built: In this formula, Yin Chen is the main herb and Hu Zhang is a supporting herb (minister), working together to clear liver-gallbladder damp-heat. Zhi Zi and Da Huang help the body expel damp-heat. Hu Zhang's job here is to assist the clearing while also helping move stasis, working with Yin Chen to ease yellowing.

Traditional use: This formula was used for damp-heat jaundice — yellowing of the skin and eyes, dark urine, a bitter dry mouth, and a greasy yellow tongue coating.

Modern note: As with any formula, use should follow proper assessment — a practitioner adjusts the pairing and dose to the type of jaundice. Do not self-administer.

Formulas vs. Single Herbs

A formula combines several herbs to create a whole effect. This is different from using a single herb in one key way:

Formulas are built for balance — different herbs cover different patterns and restrain each herb's bias.
A single herb cannot copy a full formula — the dose and pairing are designed as a whole, enabling synergy or restraint.
Do not build your own formulas from online articles, and do not take a single herb to replace a formula — the effect comes from the combination.

Diet & Daily Home Use

1. Home Tea and Simmered Dish

Two gentle, everyday ways to meet Hu Zhang:

Example 1 — Hu Zhang clearing tea:

Ingredients: about 3 g of Hu Zhang slices, 3 g of Yin Chen, and 2 g of Ju Hua.
Method: pour boiling water over all ingredients, cover, and steep for 10 minutes. It can be re-brewed until the flavor fades.
When it fits: a damp-heat constitution with mild bitter taste, sticky stools, and a greasy yellow tongue coating, without obvious cold, weak digestion.
Who should skip it: people with cold, weak digestion, pregnant women, and those with heavy menstrual flow.
Frequency: one to two times a week — not for long, continuous use.

Example 2 — Hu Zhang simmered with lean pork:

Ingredients: about 5 g of Hu Zhang slices, 100 g of lean pork, and 2 slices of Sheng Jiang (fresh ginger).
Method: cut and blanch the pork, then simmer it with the Hu Zhang and ginger in a pot with enough water on a low heat for 1.5 hours, seasoning with a little salt.
When it fits: mild damp-heat with some stasis — mild joint pain, sticky stools, slight bruises.
Who should skip it: pregnant women, people with cold, weak digestion, and those with liver or kidney concerns.
Frequency: about once every two weeks — not too often.

Please note: Hu Zhang is a dried medicinal herb, not an ordinary food. Adjust the dose under a practitioner's guidance based on your constitution.

2. Dried Herb Decocting and Processing

The raw form leans toward clearing damp-heat and easing stagnant-blood pain. The processed form (after stir-frying) is slightly gentler, suiting milder, more balanced use. For home use, Hu Zhang does not require special decocting — just simmer it with the other herbs. In a dish, mind the herb-to-food ratio and do not raise the herb dose casually.

Remember that different forms are not directly convertible — the dose in a prescription differs from the dose in a dish. Adjust to the purpose.

3. Dosage and How Long to Use

In traditional prescriptions, a common dose range of Hu Zhang is about 9 to 15 g, adjusted by a practitioner. For food-style use, about 3 to 5 g is typical — clearly different from the medicinal dose.

Hu Zhang is not meant for long-term, continuous use. Whether medicinal or food-style, use it under professional guidance, generally no longer than two weeks; if symptoms do not improve, check with a practitioner. Pregnant women, children, and older adults should strictly follow a professional's advice.

Contraindications & Safety Warnings

1. Who Should Avoid Hu Zhang

People with cold, weak digestion — frequent stomach pain, loose stools, cold hands and feet.
Pregnant and nursing women — use with care, to protect the fetus or infant.
Children and older adults — weaker body function; use only under professional guidance.
People with liver or kidney concerns — not for self-use without professional assessment.
People allergic to buckwheat-family (Polygonaceae) plants — avoid it.
People on blood thinners, blood-pressure, or diabetes medications — check with a doctor or pharmacist first.

2. Drug Interactions and Food Notes

What deserves attention here is drug interaction:

Hu Zhang may interact with blood thinners, blood-pressure, diabetes, or sedative medications, affecting how they are absorbed or broken down. Anyone on these should check with a doctor or pharmacist before self-use.
There is no solid evidence of broad "food conflicts" in the way folk stories describe. The real thing to watch is herb-drug interaction — do not casually mix herbs and foods while on medication.

3. Possible Side Effects and Overuse Risks

Hu Zhang may cause mild stomach upset — nausea, vomiting, or diarrhea. Taking too much may worsen these and could add strain on the liver and kidneys.

If you notice clear discomfort, allergic signs, ongoing vomiting, trouble breathing, confusion, or symptoms that worsen quickly, stop use and seek medical attention promptly.

Frequently Asked Questions About Hu Zhang

What is Huzhang? Is it the same as Yinchen or Dahuang?

Huzhang is the dried rhizome and root of Reynoutria japonica, Latin name Polygoni Cuspidati Rhizoma et Radix. It is a common Chinese medicine centered on draining dampness and clearing jaundice, clearing heat and detoxifying, dispersing stasis and relieving pain, and stopping cough and transforming phlegm. Yinchen drains dampness and clears jaundice. Dahuang purges downward and attacks accumulation. They cannot be used interchangeably in equal amounts. Prescribe as Huzhang. Caution in pregnancy.

What are the composition and effects of Huzhang?

Pharmacopoeial name Huzhang, Latin Reynoutria japonica Houtt. Slightly bitter in taste, slightly cold in nature, enters the Liver, Gallbladder and Lung meridians. Functions to drain dampness and clear jaundice, clear heat and detoxify, disperse stasis and relieve pain, and stop cough and transform phlegm. Used for damp-heat jaundice, turbid strangury, leukorrhea, wind-damp bi pain, abscesses and sores, burns and scalds, amenorrhea, abdominal masses, traumatic injuries, and lung heat cough. Drains dampness and disperses stasis.

How to choose between raw and processed? Can Yinchen replace it?

Rhizome is used raw. Yinchen emphasizes jaundice rather than strongly dispersing stasis, and cannot replace it in equal amounts. Commercial products are standardized; do not adjust arbitrarily.

What is the dosage of Huzhang? Can it be used daily as a jaundice-clearing tea?

Decoction, 9-15g. Modern use requires physician-determined dosage. It is not a year-round "Huzhang tea." Pregnancy will be further injured by prolonged use. Jaundice requires short-term, physician-determined dosage and cannot replace evaluation.

What are the contraindications of Huzhang? Can pregnant women use it?

Use with caution in pregnancy. Stop if loose stools or abdominal pain occur. Seek immediate medical care for severe jaundice or high fever.

Can Huzhang clear jaundice, detoxify, and disperse stasis?

It can assist damp-heat jaundice, turbid strangury, leukorrhea, wind-damp bi pain, abscesses and sores, burns and scalds, amenorrhea, abdominal masses, traumatic injuries, and lung heat cough. It drains dampness and clears jaundice, clears heat and detoxifies, disperses stasis and relieves pain, and stops cough and transforms phlegm, but is not a specific remedy for all jaundice or all cough.

Can Huzhang be taken daily as a jaundice-clearing or stasis-dispersing tea?

Damp-heat jaundice can be used short-term in formulas; pregnancy will be further injured. The idea that "Huzhang must clear jaundice" cannot replace evaluation. Draining dampness and dispersing stasis requires physician-determined formulation and dosage.

How to choose between Huzhang, Yinchen, Dahuang, Danshen, and Yuxingcao?

Huzhang drains dampness and disperses stasis, suited to damp-heat jaundice. Yinchen drains dampness and clears jaundice. Dahuang purges downward. Danshen activates blood and expels stasis. Yuxingcao clears heat and detoxifies. Choose Huzhang for clearing jaundice; Yinchen for jaundice; Dahuang for promoting bowel movements; Danshen for expelling stasis; Yuxingcao for detoxifying. Pattern differentiation applies, but large doses of Huzhang are contraindicated in pregnancy.

How is Huzhang commonly modified? What is a representative usage?

Modifications depend on the pattern. Add Yinchen for jaundice; add Honghua for traumatic injuries. Specify Huzhang; do not substitute Yinchen in equal amounts for dispersing stasis.

How to select and store Huzhang?

Choose regular Chinese medicinal materials with intact rhizomes. Discard if moldy, damp, or abnormal in odor. Store in a dry place. Purchase "Huzhang"; do not substitute Yinchen or Dahuang in equal amounts for draining dampness, clearing jaundice, and dispersing stasis.

Related Products

Nong's Hu Zhang (Japanese Knotweed Rhizome) Single Herb 5:1 Concentrated Granules $53.68

Hoi Tin Hu Zhang (Giant Knotweed Root) Single Herb 10:1 Concentrated Granules, 100 g TCM Herbal Supplement

Hoi Tin Hu Zhang (Giant Knotweed Root) Single Herb 10:1 Concentrated Granules $26.85

Medical Disclaimer — This article is provided for educational purposes only and describes traditional Chinese medicine concepts. It is not medical advice, and it is not intended to diagnose, treat, cure or prevent any disease. Always consult a qualified practitioner before using any herb, particularly if you are pregnant, nursing, taking medication or managing a diagnosed condition.