Roots and rhizomesHemostaticImperatae Rhizoma

Bai Mao Gen (Lalang Grass Rhizome)

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

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Last reviewed Oct 29, 2026

Quick Facts

Latin Name	Imperatae Rhizoma
Chinese Name & Pinyin	白茅根 · Bai Mao Gen
Medicinal Part	Roots and rhizomes
The item	Bai Mao Gen is the dried rhizome of cogongrass, a Poaceae grass. Lu Gen is not this rhizome. It usually goes into decoctions, teas, and summer soups.
Nature and channels	Sweet, cold. Enters the Lung, Stomach, and Bladder. Sweet cold clears heat, promotes urination, and clears lung-stomach heat.
Pharmacopoeia line	Clears heat and promotes urination, cools the blood and stops bleeding. Used for edema with urinary difficulty, urinary burning, dry mouth and thirst, vomiting blood, and nosebleed.
Pattern cues	Scanty dark urine. Mild edema. Dry mouth and thirst. Sore throat. Bleeding gums.
In this article	Bai Mao Gen versus Lu Gen. Draining downward versus moistening upward. Why the dose is modest. Why spleen-stomach cold is a caution. Who should skip it.

What Is Bai Mao Gen?

Bai Mao Gen (白茅根; Bái Máo Gēn; Latin: Imperatae Rhizoma; English: cogongrass rhizome) in the current pharmacopoeia is the dried rhizome of Imperata cylindrica, a Poaceae grass, dug in spring and autumn, washed, and dried whole or in segments. It is sweet and cold, enters the Lung, Stomach, and Bladder channels, and its core actions are to clear heat and promote urination, and to clear lung-stomach heat and cool the blood. It usually goes into decoctions, teas, and light summer soups. The usual amount is 10–15 g per day. It needs no special timing in a decoction. In daily care it appears in small-dose teas with Lu Gen and Mai Dong.

It is not Lu Gen. Reed rhizome is also cold and sweet, entering the Lung and Stomach, but it leans upward and moistening, focused on generating fluids to stop thirst; Bai Mao Gen also drains downward through the urine, suiting those with scanty dark urine and mild edema. Spleen-stomach cold, easy diarrhea, and cold hands and feet, with no heat signs, is a poor match. Pregnancy and breastfeeding need a clinic first.

It is used most often for three patterns:

Damp-heat moving downward: scanty dark urine, urinary burning, mild edema with a dry mouth
Lung-stomach heat: dry mouth and throat, sore swollen throat, bleeding gums, light cough
Summer home care: cooling teas and light soups for heat and thirst

Sweet and cold, it is not a daily “cooling root tea” to keep increasing. Clearing when there is no heat deepens spleen-stomach cold and may bring diarrhea and stomach pain.

When damp-heat moves downward, the urine turns scanty and dark and mild edema appears; when lung-stomach heat rises, the mouth dries, the throat swells, and the gums may bleed. Bai Mao Gen is sweet and cold. It clears heat without being harshly bitter, frees the urine, and eases mild bleeding, which is why it appears in Bai Mao Gen Tang (Cogongrass Rhizome Decoction)–type formulas. It drains more than it tonifies. A cold weak stomach, with no heat, gets worse if more is added.

Bai Mao Gen is not a catch-all cooling or urinary root. In spleen-stomach cold, with no heat signs, or in pregnancy, using it alone is a poor match. Raw or honey-fried, and whether it belongs in a formula, should be decided by a licensed Chinese medicine practitioner after pattern diagnosis.

Bai Mao Gen: Materia Medica Profile

Identification & Quality Standard

Imperatae Rhizoma

Botanical Origin

The dried rhizome of Imperata cylindrical (Linn.) P. Beauv. (Gramineae).

Production Regions

Primarily produced in northern Chinese provinces, including Henan, Liaoning, Hebei, Shaanxi, Shandong, Shanxi, and Xinjiang.

Quality Requirements

Superior medicinal material is thick, white and sweet.

Macroscopic Features

Rhizome is long cylindrical shape, or has branches, variable length, 30~60cm long, 2~4mm diameter. Externally yellowish-white or pale yellow, lustrous; presents longitudinal wrinkles and obvious circular joints, with grayish-brown bulb and small roots on the joints, internode is 1~3cm long. Light in substance, tenacious texture, fibrous fractured surface; yellowish-white, with radial cracks, or with one hole in the center. faint odor; taste slightly sweet.

Main Regions and Quality Identification

Traditional materia medica and industry experience value certain producing regions, though actual quality also depends on variety, harvest time, processing, and storage. Bai Mao Gen grows mainly in the northeast, north, northwest, southwest, and east of China, with some differences in rhizome thickness and scent between regions. Good-quality rhizomes are slender and evenly thick, yellowish-white and lustrous on the surface, fairly hard yet slightly tough, with radiating striations on the cut face and a faint sweet scent. The raw cut face shows a yellowish-white pith at the center; the honey-fried form is old-yellow on the surface with a honey aroma and a sweet taste. Common look-alikes are the rhizomes of other grasses in the same family — distinguish them by the nodes: Bai Mao Gen has longer internodes with finer rootlets, while look-alikes have shorter internodes and denser rootlets.

Traditional Properties & Historical Lineage

Nature, Flavour & Channel Tropism

Sweet; ColdLungStomachBladder

1. Records in Classic Materia Medica

Shen Nong Ben Cao Jing: listed as a middle-grade herb; "treats overwork and emaciation, supplements the middle and boosts qi, removes static blood and blood-closure with cold-heat, and promotes urination."
Ming Yi Bie Lu: adds that it "resolves the five strangury, clears guest heat in the stomach and intestines, stops thirst, firms the sinews, and treats uterine bleeding."
Xin Xiu Ben Cao: notes it "treats irregular menstruation and unblocks blood-vessel dribbling."
Ben Cao Gang Mu: records it "stops vomiting of blood and the various bleedings, treats cold-damage hiccup, lung-heat panting, edema, jaundice, and relieves alcohol toxicity."

These records circle around its clearing-draining and protective actions, never treating it as a cure-all.

2. How Views of Its Nature Changed

Different physicians saw it differently. Some stressed its clearing-draining side — clearing internal heat and promoting urination. Others emphasized its protective side — that it can gently support the body, suiting mild deficiency-heat. Still others defined its limits — that those with spleen-stomach cold and no clear heat should not overuse it, lest the cold nature worsen their discomfort. These differing emphases reflect the herb's gentle character, and show that its use should always be matched to the individual's actual condition.

Core Efficacies & Traditional Applications

Traditional Functions

Cools blood and stops bleeding, and clears heat and promotes diuresis.

1. First Direction: Clearing Heat and Promoting Urination

Traditional action: Bai Mao Gen is traditionally regarded as clearing heat and promoting urination — removing internal heat, freeing the urine, and helping the body expel excess damp and heat-turbidity.
Typical signs: marked heat signs with scanty dark urine, urinary discomfort, or mild edema — for example, summer-heat-driven yellow urine with urinary burning, or mild lower-limb edema with a dry mouth and thirst.
Usual combinations: in practice it is often paired with urine-promoting herbs such as Che Qian Zi and Hua Shi, and with lung-heat-clearing herbs such as Lu Gen, to also address upper-burner heat.
Who should not self-use: those with spleen-stomach cold — frequent diarrhea, cold hands and feet — and no obvious heat signs, since the cold nature may worsen stomach discomfort.

2. Second Direction: Clearing Lung-Stomach Heat

Traditional action: Bai Mao Gen is traditionally regarded as clearing lung-stomach heat, easing the discomfort that excess lung-stomach heat brings.
Typical signs: lung-stomach heat with dry mouth and thirst, a sore swollen throat, bleeding gums, or a light cough with little phlegm — for example, gum redness and bleeding after spicy food, or a mild lung-heat cough.
Usual combinations: in practice it is often paired with lung-stomach heat-clearing herbs such as Shi Gao and Zhi Mu, and with bleeding-stopping herbs such as Ou Jie to ease gum or throat bleeding.
Who should not self-use: those with spleen-stomach cold, easy acid reflux, or stomach pain — the heat is cleared, but the cold may deepen the stomach's cold-deficiency symptoms.

3. Classic Pairing: Bai Mao Gen With Lu Gen

The classic herb pair is Bai Mao Gen with Lu Gen. Bai Mao Gen enters the lung, stomach, and bladder, focusing on clearing lung-stomach heat and promoting urination; Lu Gen enters the lung and stomach, focusing on clearing lung-stomach heat and generating fluids to stop thirst. Together they coordinate, strengthening the lung-stomach heat clearing while also generating fluids — suiting the lung-stomach heat pattern of dry mouth and thirst, a light cough with little phlegm, and scanty dark urine. Note that this pairing needs a practitioner's pattern diagnosis — don't combine herbs on your own.

Modern Research

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

1. Main Chemical Constituents

Modern analysis has detected carbohydrates, triterpenoids, flavonoids, and organic acids in Bai Mao Gen. Carbohydrates are among its main nutritional components; certain triterpenoids have shown some bioactivity in vitro; some flavonoids have shown related effects in animal studies. As for these components in humans, no firm clinical efficacy conclusions have yet been reached.

2. Current Research Directions

Work on Bai Mao Gen mainly centers on exploring the activity of its constituents. Experiments have observed that some components may have certain bioactivity, but most of these observations come from in vitro or animal studies — more human research is still needed to verify their actual effects in people.

3. Limitations of Current Research

Lab results are not clinical efficacy — in vitro and animal findings cannot be directly equated with what happens after a person takes the herb.
Extracts and monomers are not the same as traditional decoction pieces — the extract doses used in experiments differ greatly from the amounts of cut herb taken daily.
Methods and doses vary between studies, which can produce large differences in results and make unified conclusions hard to reach.
A single component does not define the whole herb — Bai Mao Gen's effect comes from many components working together; one component's activity cannot represent the whole.

Comparing Similar Herbs

1. What They Share

Lu Gen is chosen here as the comparable herb, since its actions are close to Bai Mao Gen's. They share: clearing lung-stomach heat; use for the lung-stomach heat pattern of dry mouth and throat discomfort; frequent appearance in summer heat-clearing food therapy and formulas; and the need for attention to constitution and dose — neither should be overused or taken long-term.

2. The Key Differences: Bai Mao Gen vs. Lu Gen

Nature and flavors: Bai Mao Gen is cold, sweet, entering the lung, stomach, and bladder, gentle in nature, clearing and protecting at once; Lu Gen is also cold, sweet, entering the lung and stomach, but leans toward clear-moistening, with its protective side aimed more at generating fluids.
Focus: Bai Mao Gen also promotes urination on top of clearing lung-stomach heat — suiting those who also have scanty dark urine or mild edema; Lu Gen focuses more on generating fluids and stopping thirst — suiting those with marked dry mouth and fluid insufficiency.
Qi tendency: Bai Mao Gen clears and drains downward — the heat and damp leave through the urine, without wasting fluids; Lu Gen moistens and clears upward — relieving lung-stomach dryness by replenishing fluids.
Best fit: Bai Mao Gen's traditional indications are scanty dark urine, urinary discomfort, and mild edema with a dry mouth; Lu Gen's are dry mouth, sore throat, and a light cough with little phlegm — where fluid insufficiency shows more clearly.
Not suitable: Bai Mao Gen is unsuitable for spleen-stomach cold without clear heat, and for the diarrhea-prone; Lu Gen is also unsuitable for spleen-stomach cold, but because it is more clear-moistening, extra caution is needed in those with damp-heavy spleen and a thick greasy tongue coat.
Use scenes: Bai Mao Gen appears more in scenes needing urine promotion — summer mild edema regulation, easing urinary burning; Lu Gen appears more in scenes needing fluid generation — dry mouth regulation, easing a light cough with little phlegm.

3. One-Sentence Summary

Simply put, Bai Mao Gen leans toward clearing, draining downward, and promoting urination, whereas Lu Gen leans toward clearing, moistening upward, and generating fluids. Both can be used for lung-stomach heat discomfort, but they are not interchangeable.

Classical Formulas Containing Bai Mao Gen

Classic Formula 1: Bai Mao Gen Tang (Cogongrass Rhizome Decoction)

Combination logic: Bai Mao Gen is the lord, clearing heat and promoting urination to address retained heat and damp. It is paired with Che Qian Zi and Hua Shi to strengthen the heat-clearing and urination-promoting effect, and with Mu Tong to further free the urine and help expel turbid pathogenic qi. The formula does not use Bai Mao Gen alone, because a single herb cannot cover the several facets of the pattern — multiple herbs working together achieve the better result.

Traditional use: the formula was traditionally used for damp-heat moving downward — scanty dark urine, urinary burning, and mild edema — helping clear the damp-heat and free the urine.

Modern note: modern clinical use requires a doctor's pattern diagnosis and standard care. A formula name that sounds related to urinary disease does not mean you should apply it to yourself.

Classic Formula 2: Mao Gen Yin (Cogongrass Rhizome Drink)

Combination logic: Bai Mao Gen is the minister, clearing lung-stomach heat and strengthening the lord Lu Gen's heat-clearing, while herbs such as Ou Jie ease possible gum or throat bleeding. The formula does not use Bai Mao Gen alone, because a single herb cannot cover both clearing lung-stomach heat and generating fluids — it needs other herbs to work together.

Traditional use: the formula was traditionally used for lung-stomach heat excess — dry mouth and thirst, red swollen gums, and a light cough with little phlegm — helping clear the lung-stomach heat and ease the discomfort.

Modern note: modern clinical use requires a doctor's pattern diagnosis and standard care; do not self-apply just because the name relates to respiratory or oral disease.

Formulas vs. Single Herbs

A formula is the result of many herbs working together; a single herb cannot simply replicate a full formula's effect. The formula's doses and combinations are holistic — the herbs strengthen or restrain one another, forming one unified regulating direction. A common misunderstanding: that because a herb works inside a formula, taking it alone will work the same way. It will not — the formula's effect is synergy among components, a single herb's power is limited, and dose and method differ. So don't build your own formula from online articles; casual combining can bring discomfort.

Diet & Daily Home Use

1. Home Teas and Soups

Tea — Bai Mao Gen Qing Run Tea: Sheng Bai Mao Gen 10 g, Lu Gen 5 g, Mai Dong 3 g. Wash the ingredients, put them in a cup, steep in boiling water for 10 minutes, and drink; can be re-steeped until the taste fades. Suited to summer dry mouth and thirst, a light cough, and scanty dark urine in daily regulation. Not for those with spleen-stomach cold or easy diarrhea. Suggested: 2–3 times a week, one cup each time; not for long-term continuous use. Note: Bai Mao Gen is a medicinal herb, not an ordinary food — choose properly processed pieces from reliable channels.

Soup — Bai Mao Gen with Dong Gua: Sheng Bai Mao Gen 15 g, Dong Gua 50 g, Sheng Jiang 2 slices. Wash and cut the Bai Mao Gen into segments, peel and cut the gourd into pieces, put all with the ginger in a pot with water, boil 20 minutes, and season lightly with salt. Suited to summer mild edema and a dry mouth. Not for those with spleen-stomach cold. Suggested: once every two weeks, one bowl each time.

2. Decoction and Processing Differences

The raw and processed forms differ mainly in effect and scene. Sheng Bai Mao Gen leans toward clearing heat and promoting urination — for urinary discomfort and edema; Mi Zhi Bai Mao Gen (honey-fried) leans toward clear-moistening and generating fluids — for dry mouth and cough. At home, raw Bai Mao Gen can be decocted together with other herbs with no special handling; the honey-fried form can also be decocted directly, with no pre-boiling or late-addition steps. Different forms cannot be converted directly: 10 g of raw Bai Mao Gen and 10 g of honey-fried Bai Mao Gen are not the same in effect, and cannot simply be exchanged by dose.

3. Dosage and Course

The common dose in traditional prescriptions is 10–15 g per day; food-therapy doses can be reduced to 5–10 g. Food-therapy doses are lower, for gentle daily regulation; medicinal doses are higher, for treating a pattern. Long-term continuous use is not advised: a course of 3–5 days is usually enough, and if symptoms don't improve, consult a doctor or pharmacist. Special groups — pregnant women, children, the elderly — should adjust the dose to their condition and consult a professional when needed.

Contraindications & Safety Warnings

1. Who Should Avoid It

Spleen-stomach cold — those with frequent diarrhea, cold hands and feet, and no obvious heat signs.
Pregnancy and breastfeeding — consult a doctor before use.
Children and the elderly — weaker body functions; use only under a doctor.
Liver or kidney impairment — consult a doctor before use.
Allergy to Bai Mao Gen or to grasses (Poaceae plants) — avoid it.
Those in special treatment — people on anticoagulant, blood-pressure, or blood-sugar medications should consult a doctor first.

2. Interactions and Diet Notes

Bai Mao Gen may interact with anticoagulants, blood-pressure medications, and blood-sugar medications — for example, it may strengthen an anticoagulant's effect or affect the action of blood-pressure and blood-sugar drugs. If you take any of these, consult a doctor or pharmacist before use. There is no sufficient evidence for a general "food clash" between ordinary foods, but certain herbs can interact with specific drugs — anyone on medication should ask first.

3. Adverse Reactions and Overdose Risk

Taking too much can deepen spleen-stomach cold — diarrhea, stomach pain — or bring cold-related body discomfort. If marked discomfort, allergy signs, persistent vomiting, breathing difficulty, altered consciousness, or rapidly worsening symptoms appear, stop at once and seek medical care — don't delay treatment.

Frequently Asked Questions About Bai Mao Gen

What is Bai Mao Gen? Are Lu Gen and Xiao Ji the same?

Bai Mao Gen (白茅根) is the dried rhizome of Imperata cylindrica (Imperatae Rhizoma), a common Chinese herb centered on cooling the blood and stopping bleeding, clearing heat and promoting urination, and clearing Lung-Stomach heat. Lu Gen clears heat and generates fluids, leaning to Lung-Stomach heat. Xiao Ji cools the blood and stops bleeding, leaning to blood heat bleeding. The three cannot be interchanged by equal weight. Write Bai Mao Gen. Use caution in Spleen-Stomach vacuity cold.

What is the composition and traditional use of Bai Mao Gen?

Pharmacopoeial name Bai Mao Gen, Latin Imperata cylindrica. Sweet and cold; enters the Lung, Stomach and Bladder channels. It acts to cool the blood and stop bleeding, clear heat and promote urination, and clear Lung-Stomach heat. It is used for blood heat hematemesis, epistaxis and hematuria, heat disease with vexation and thirst, damp-heat jaundice, edema with scanty urine, heat strangury with rough pain, Stomach heat vomiting, and Lung heat cough. Cools the blood, clears heat and promotes urination.

How do you choose raw versus prepared? Can Lu Gen replace it?

Dried cut into sections or charred. Lu Gen leans to clearing heat and generating fluids without heavy blood-cooling and bleeding-stopping; it cannot replace the formula by equal weight. Commercial products follow regulated processing; do not self-modify.

What is the usual dosage? Can it be drunk daily as a blood-cooling tea?

Decocted, 9-30 g, fresh 30-60 g. Modern use requires a practitioner to name the dose. It is not a four-season “Imperata tea.” Spleen-Stomach vacuity cold only injures further. Blood heat bleeding needs a practitioner to name a short course; it does not replace assessment.

What are the contraindications? Can it be used in pregnancy?

Use caution in Spleen-Stomach vacuity cold and vomiting from middle burner cold. Pregnancy requires practitioner assessment. Stop if loose stool or abdominal pain appears. Unceasing bleeding or high fever need immediate medical care.

Can Bai Mao Gen cool the blood and stop bleeding, clear heat and promote urination?

It can help blood heat hematemesis, epistaxis and hematuria, heat disease with vexation and thirst, and edema with heat strangury. It cools the blood and stops bleeding, clears heat and promotes urination, and clears Lung-Stomach heat—not a specific for every bleeding or every edema.

Can Bai Mao Gen be drunk daily as a blood-cooling, bleeding-stopping or diuretic tea?

Blood heat bleeding may enter a short formula; Spleen-Stomach vacuity cold only injures further. “Imperata must cool the blood” does not replace assessment. Cooling the blood and stopping bleeding, clearing heat and promoting urination should be named by a practitioner with form and dose.

How do you choose among Bai Mao Gen, Lu Gen, Xiao Ji, Ou Jie and Ce Bai Ye?

Bai Mao Gen cools the blood and stops bleeding while clearing heat and promoting urination, leaning to blood heat bleeding and heat strangury. Lu Gen clears heat and generates fluids, leaning to Lung-Stomach heat. Xiao Ji cools the blood and stops bleeding, leaning to blood heat bleeding. Ou Jie astringes and stops bleeding, leaning to various bleeding. Ce Bai Ye cools the blood and stops bleeding, leaning to blood heat bleeding. Blood heat bleeding and heat strangury favor Bai Mao Gen; Lung-Stomach heat favors Lu Gen; blood heat favors Xiao Ji; astringing favors Ou Jie; blood heat favors Ce Bai. They may be referenced after pattern differentiation; Spleen-Stomach vacuity cold forbids large Bai Mao Gen.

How is Bai Mao Gen commonly modified? What is the representative use?

Depends on the pattern. Bleeding may add Xiao Ji and Ou Jie; heat strangury may add Che Qian Zi. Write Bai Mao Gen; do not replace the blood-cooling action with an equal weight of Lu Gen.

How do you choose and store Bai Mao Gen?

Choose regulated Chinese medicinal materials with intact rhizomes. Moldy, damp, or abnormal-smelling lots are discarded. Store cool and dry. Buy “Bai Mao Gen”; do not replace cooling the blood and stopping bleeding, clearing heat and promoting urination with an equal weight of Lu Gen or Xiao Ji.

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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.