Herb Stem (茎 jīng)

Xiao Tong Cao

Stachyurus pith · 小通草

Stachyurus himalaicus Hook.f. et Thoms. · Medulla Stachyuri

Also known as: Xiao Tong Hua (小通花)

Xiao Tong Cao (Stachyurus pith) plant

Images shown are for educational purposes only

Xiǎo Tōng Cǎo is a lightweight, mild herb primarily used to promote urination and support breast milk production. It gently clears Heat from the urinary system and is commonly added to postpartum recipes or formulas for women with low milk supply. It is also used for mild urinary tract discomfort with dark or scanty urine.

Category Dampness-draining herbs (利水渗湿药)
Therapeutic focus Urinary Health Breastfeeding and Lactation Support Fluid Balance

TCM Properties

Temperature

Cold

Taste

Sweet (甘 gān), Bland (淡 dàn)

Channels entered

Lungs, Stomach, Urinary Bladder

Parts used

Stem (茎 jīng)

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Educational content • Consult qualified TCM practitioners for diagnosis and treatment

What This Herb Does

Every herb has a specific set of actions — here's what Xiao Tong Cao does in the body, explained in both everyday and TCM terms

Therapeutic focus

In practical terms, Xiao Tong Cao is primarily used to support these areas of health:

Urinary Health Breastfeeding and Lactation Support Fluid Balance

TCM Actions

In TCM terminology, these are the specific therapeutic actions that Xiao Tong Cao performs to restore balance in the body:

Clears Heat and Promotes Urination Promotes Lactation Drains Dampness

How these actions work

'Clears Heat and promotes urination' means Xiǎo Tōng Cǎo helps the body expel excess Heat through the urine. Its cold, bland nature allows it to gently leach out Dampness and Heat that have accumulated in the urinary tract. This is why it is used when someone experiences painful, scanty, or dark-yellow urination due to Damp-Heat. Unlike stronger herbs that drain the urinary system, Xiǎo Tōng Cǎo acts mildly and does not easily injure the body's fluids, making it suitable for milder cases of urinary difficulty.

'Promotes lactation' refers to the herb's ability to help restore breast milk flow in nursing mothers. In TCM thinking, breast milk is closely related to the Stomach channel's Qi rising upward. Because Xiǎo Tōng Cǎo enters the Lung and Stomach channels, it can both raise Stomach Qi upward to the breasts and open the channels through which milk flows. It is a commonly used assistant herb in postpartum formulas for insufficient or absent lactation.

'Drains Dampness' describes its broader role as a mild diuretic. The bland taste in TCM is specifically associated with seeping and leaching out excess fluids. This makes Xiǎo Tōng Cǎo useful for mild edema or water retention, particularly when there is accompanying Heat.

Patterns Addressed

In TCM, symptoms cluster into recognizable patterns of disharmony. Xiao Tong Cao is used to help correct these specific patterns.

Why Xiao Tong Cao addresses this pattern

Xiǎo Tōng Cǎo directly addresses Damp-Heat accumulating in the Lower Jiao (lower abdomen and urinary system). Its cold nature clears Heat, while its bland taste seeps out Dampness through the urine. By entering the Lung and Urinary Bladder channels, it helps restore the normal downward flow of fluids, relieving urinary obstruction. The Lungs govern the water passages from above, and when Lung Qi is cleared, fluid descends properly to the Bladder for excretion. This makes the herb well-suited for painful, scanty, or dark urination caused by Damp-Heat lodged in the urinary tract.

A practitioner would look for one or more of these signs

Painful Urination

Burning or stinging sensation during urination

Dark Urine

Dark yellow or reddish urine

Urinary Difficulty

Scanty urine output or dribbling

Edema

Mild swelling of the lower limbs

Commonly Used For

These are conditions where Xiao Tong Cao is frequently used — but only when they arise from the specific patterns it addresses, not in all cases

Arises from: Damp-Heat in the Lower Burner

TCM Interpretation

TCM understands urinary tract infections primarily as Damp-Heat accumulating in the Urinary Bladder. Dampness is a heavy, turbid pathogenic factor that obstructs the normal flow of fluids, while Heat causes inflammation, burning pain, and darkened urine. The condition involves a failure of the Bladder's normal function of storing and excreting urine, often compounded by a disruption in the Lung's role in governing the downward movement of body fluids.

Why Xiao Tong Cao Helps

Xiǎo Tōng Cǎo's cold nature directly counteracts the Heat component, while its bland taste promotes the gentle leaching of Dampness through increased urination. By entering the Lung and Urinary Bladder channels, it restores the normal downward flow of fluids from above (Lungs) to below (Bladder), helping to flush out the pathogenic Damp-Heat. Its action is mild, which makes it appropriate as an assistant herb in urinary formulas rather than as a standalone treatment for severe infections.

Also commonly used for

Edema

Mild water retention, particularly in the lower body

Oliguria

Scanty urine output

Urinary Difficulty

Difficulty urinating or dribbling urination

Herb Properties

Every herb has an inherent temperature, taste, and affinity for specific channels — these properties determine how it interacts with the body

Temperature

Cold

Taste

Sweet (甘 gān), Bland (淡 dàn)

Channels Entered

Lungs Stomach Urinary Bladder

Parts Used

Stem (茎 jīng)

Dosage & Preparation

These are general dosage guidelines for Xiao Tong Cao — always follow your practitioner's recommendation, as dosages vary based on the formula and your individual condition

Standard dosage

3-6g

Maximum dosage

Up to 9g in acute urinary conditions, under practitioner supervision. The herb is very lightweight and mild, so exceeding 9g is rarely necessary.

Dosage notes

Use the lower end of the range (3g) for mild urinary discomfort or as a supporting herb in lactation-promoting formulas. Use the higher end (5-6g) for more pronounced urinary difficulty, damp-heat lin syndrome, or water retention. Because the herb is very light in weight, even small gram amounts represent a considerable volume of material. Prolonged use at higher doses should be monitored to avoid excessive fluid depletion, particularly in elderly or weak patients.

Preparation

No special decoction handling required. Decoct normally with other herbs. The pieces are very light and may float; some practitioners place them in the decoction pot after the water has been added. Cut into short segments before decocting for even extraction.

Common Herb Pairs

These ingredients are traditionally combined with Xiao Tong Cao for enhanced therapeutic effect

Wang Bu Liu Xing
Wang Bu Liu Xing Wang Bu Liu Xing 9g : Xiao Tong Cao 6g

Wang Bu Liu Xing (Vaccaria seed) invigorates Blood and unblocks the channels, while Xiao Tong Cao raises Stomach Qi to the breasts and opens the milk pathways. Together they address both the Blood stasis and Qi stagnation components of blocked lactation, producing a stronger milk-promoting effect than either herb alone.

When to use: Postpartum insufficient lactation, especially when the breasts feel distended or lumpy, suggesting channel obstruction alongside deficiency.

Che Qian Zi
Che Qian Zi Che Qian Zi 15g : Xiao Tong Cao 6g

Che Qian Zi (Plantago seed) clears Heat and strongly promotes urination, while Xiao Tong Cao gently leaches Dampness and facilitates the Lung's regulation of water passages. Together they create a comprehensive diuretic action that addresses both the upper source (Lung) and lower drainage (Bladder) of fluid metabolism.

When to use: Damp-Heat urinary conditions with painful, scanty, dark urine or mild edema.

Huang Qi
Huang Qi Huang Qi 30g : Xiao Tong Cao 6-9g

Huang Qi powerfully tonifies Spleen and Lung Qi and generates Blood, addressing the root deficiency behind low milk supply. Xiao Tong Cao opens the channels and directs Qi upward to the breasts, ensuring the newly generated Qi and Blood can reach where they are needed for lactation.

When to use: Postpartum milk insufficiency due to Qi and Blood Deficiency, with fatigue and poor appetite.

Comparable Ingredients

These ingredients have overlapping uses — here's how to tell them apart

Tong Cao
Xiao Tong Cao vs Tong Cao

Tong Cao (Medulla Tetrapanacis, from the rice paper plant) and Xiao Tong Cao share very similar actions: both clear Heat, promote urination, and support lactation. Tong Cao is considered slightly stronger in its diuretic effect. In modern practice, the two are often used interchangeably. The Chinese Pharmacopoeia lists them as separate drugs from different plant sources. If the clinical picture requires stronger fluid drainage, Tong Cao may be preferred; for milder cases, Xiao Tong Cao is gentler.

Mu Tong
Xiao Tong Cao vs Mu Tong

Both promote urination and support lactation, but Mu Tong is bitter and cold, giving it much stronger Heat-clearing and descending power. Mu Tong excels at clearing Heart and Small Intestine Fire (for mouth ulcers, irritability with dark urine), while Xiao Tong Cao is bland and gentle, better suited for mild Damp-Heat without strong Fire signs. Mu Tong can injure Yin with prolonged use, whereas Xiao Tong Cao is far less harsh on the body.

Deng Xin Cao
Xiao Tong Cao vs Deng Xin Cao

Deng Xin Cao (rush pith) is also bland, light, and enters the Lung channel to promote urination and clear Heat. Classical texts compare the two as having similar mechanisms. However, Deng Xin Cao is more specifically indicated for Heart Heat causing irritability and insomnia (especially in children), while Xiao Tong Cao has a stronger reputation for promoting lactation.

Common Substitutes & Adulterants

Related species and common adulterations to be aware of when sourcing Xiao Tong Cao

The most common source of confusion is between Xiao Tong Cao and the larger Tong Cao (Da Tong Cao, 大通草, from Tetrapanax papyriferus). They are often mixed up or used interchangeably in markets, but they are different herbs from different plant families with somewhat different properties. Key distinguishing features: Xiao Tong Cao is thinner (0.5 to 1 cm diameter), solid with no hollow centre, and has a mucilaginous feel when soaked. Tong Cao is thicker (1 to 2.5 cm), has a characteristic hollow centre or translucent membrane, and is not mucilaginous when soaked. Known adulterants include stem piths from Hydrangea species (such as Hydrangea yunnanensis or western China Hydrangea), identifiable by the presence of calcium oxalate needle crystals under microscopy. Other reported substitutes include Hemo (合萌, Aeschynomene indica), whose pith is hard and shows concentric rings in cross-section, and Ci Wu Jia (刺五加, Eleutherococcus senticosus) pith. These are generally harder, non-elastic, and lack the mucilaginous quality of authentic material.

Educational content — always consult a qualified healthcare provider or TCM practitioner before using any herb.

Toxicity Classification

Classical Chinese pharmacopoeia toxicity rating for Xiao Tong Cao

Non-toxic

Xiao Tong Cao is classified as non-toxic in classical and modern sources. No toxic components have been identified in the stem pith. No cases of poisoning from standard use have been reported. The main safety concern is overuse of its diuretic properties, which may lead to excessive fluid loss in vulnerable individuals.

Contraindications

Situations where Xiao Tong Cao should not be used or requires extra caution

Caution

Pregnancy. Xiao Tong Cao promotes urination and has mild downward-moving properties that could theoretically affect the fetus. Classical sources list pregnant women as a contraindicated population.

Caution

Excessive urination or copious clear urine (polyuria). The herb's diuretic action would worsen fluid depletion in those already urinating excessively.

Caution

Qi deficiency without dampness or heat. As a bland, draining herb, Xiao Tong Cao can further deplete Qi and fluids when there is no pathological dampness or heat to clear.

Caution

Yin deficiency with dry symptoms. The herb's diuretic nature can consume fluids and aggravate dryness in Yin-deficient patients.

Special Populations

Important considerations for pregnancy, breastfeeding, and pediatric use

Pregnancy

Classical sources explicitly state that pregnant women should avoid Xiao Tong Cao (孕妇忌用). The herb promotes urination and has a draining, downward-moving quality that is generally considered unsuitable during pregnancy. While no specific teratogenic mechanism has been identified, the general principle in TCM of avoiding draining and downward-moving herbs during pregnancy applies here. It should be avoided or used only under close practitioner supervision if clinically necessary.

Breastfeeding

Xiao Tong Cao is traditionally used to promote lactation (Tong Ru, 通乳) in postpartum women with insufficient breast milk, and is considered safe and beneficial during breastfeeding at standard doses. It is commonly combined with herbs like Wang Bu Liu Xing and Huang Qi in formulas for promoting milk flow. No adverse effects on breast milk quality or the nursing infant have been reported. This is one of the few herbs that is specifically indicated for use during breastfeeding.

Children

May be used in children at reduced doses appropriate to age and body weight, typically one-third to one-half of the adult dose. It is mild and non-toxic, and has been included in paediatric formulas for urinary difficulty. However, its draining nature means it should be used cautiously in young children to avoid excessive fluid loss. Not suitable for infants without practitioner guidance.

Drug Interactions

If you are taking pharmaceutical medications, be aware of these potential interactions with Xiao Tong Cao

No well-documented pharmaceutical drug interactions have been established for Xiao Tong Cao. Given its diuretic action, there is a theoretical possibility of additive effects when used alongside pharmaceutical diuretics (such as furosemide or hydrochlorothiazide), potentially increasing fluid and electrolyte loss. Patients taking diuretic medications should inform their healthcare provider before using this herb. No other specific pharmacological interactions have been identified in the literature.

Dietary Advice

Foods and dietary considerations when taking Xiao Tong Cao

During use, favour warm fluids and easily digestible foods to support the herb's function of promoting fluid movement. Avoid excessively cold or iced beverages, which may impair the Spleen's ability to transform fluids. No specific food incompatibilities are recorded for this herb.

Botanical Description

Physical characteristics and morphology of the Xiao Tong Cao source plant

Stachyurus himalaicus (Himalayan Stachyurus) is a deciduous shrub or small tree reaching 3 to 5 metres in height, with dark brown bark. The leaves are alternate, papery to thinly leathery, lance-shaped to oblong-lanceolate, 8 to 13 cm long and 3.5 to 5.5 cm wide, with finely serrated margins and distinctive purplish-red petioles. In spring (March to April), pendulous axillary spike-like racemes of small yellow flowers appear, each with 4 petals and 8 stamens. The fruit is a nearly spherical berry. The plant grows in mountain slopes, valley edges, and forest understories or scrublands at elevations of 400 to 3,000 metres.

The medicinal part is the dried stem pith (茎髓), which is white, lightweight, and spongy. Several related species in the Stachyurus genus and Helwingia japonica (Cornaceae) also provide stem pith used as Xiao Tong Cao.

Sourcing & Harvesting

Where Xiao Tong Cao is sourced, when it's harvested or collected, and how to assess quality

Harvesting season

Autumn. Young stems are cut, trimmed of overly thin or thick sections, and the white pith is pushed out with a thin stick, straightened, and sun-dried.

Primary growing regions

Sichuan and Shaanxi provinces are traditionally considered the primary production areas. The plant is widely distributed across southwestern China and also found in Guizhou, Yunnan, Hubei, Hunan, Guangdong, Guangxi, Zhejiang, Jiangxi, Fujian, and Taiwan. Related species extend into Nepal, Bhutan, northern India (Assam), and northern Myanmar. The herb does not have a strongly defined single dao di (terroir) region, but Sichuan material is historically the most recognized.

Quality indicators

Good quality Xiao Tong Cao from Stachyurus species (Jing Jie Hua type) appears as cylindrical sticks 30 to 50 cm long and 0.5 to 1 cm in diameter. The surface should be white or pale yellow, with no visible grain or texture. The pith is lightweight and soft, compressible with the fingers and bounces back (elastic), and easy to snap. The cross-section is flat, solid (no hollow centre, which distinguishes it from the larger Tong Cao), and shows a silvery-white sheen. When soaked in water, it should feel slippery or mucilaginous. There should be no smell and no taste. Avoid pieces that are hard, darkened, discoloured, or that show a hollow centre (which may indicate substitution with Tong Cao or an adulterant).

Classical Texts

Key passages from the classical Chinese medical texts that describe Xiao Tong Cao and its therapeutic uses

《四川中药志》(Sichuan Materia Medica): First formally recorded Xiao Tong Cao as a distinct medicinal substance from the stem pith of Stachyurus species, classifying it under herbs that promote urination and drain dampness.

《中药大辞典》(Great Dictionary of Chinese Materia Medica):
性平，味淡，无毒。入肺、胃二经。功能主治：利尿渗湿。治热病小便赤黄或尿闭，湿热瘙、淋等症。
"Neutral in nature, bland in flavour, non-toxic. Enters the Lung and Stomach channels. Functions: promotes urination and drains dampness. Treats hot diseases with dark yellow urine or urinary blockage, damp-heat itching, and lin syndrome (painful urination)."

《本草正义》(Ben Cao Zheng Yi): While primarily discussing Tong Cao (通草, the larger species), this text describes the general principle shared by both herbs: 此物无气无味，以淡用事，故能通行经络，清热利水 — "This substance has no aroma and no strong flavour; it works by blandness, and can therefore open the channels, clear heat, and promote water movement." This principle applies equally to Xiao Tong Cao, which shares the same bland, draining character.

Historical Context

The history and evolution of Xiao Tong Cao's use in Chinese medicine over the centuries

Xiao Tong Cao is a relatively modern distinction in the Chinese pharmacopoeia. Historically, the names "Tong Cao" (通草) and "Tong Tuo Mu" (通脱木) were used somewhat interchangeably for several different stem-pith herbs. The confusion runs deep: in ancient texts, what was called "Tong Cao" was actually the woody vine now called Mu Tong (木通), while what we now call Tong Cao (the pith of Tetrapanax papyriferus) was referred to as "Tong Tuo Mu." The Sichuan Materia Medica (《四川中药志》) was among the first sources to formally distinguish Xiao Tong Cao ("small Tong Cao") as a separate herb derived from Stachyurus species.

The name "Xiao" (小, small) refers to the herb's thinner diameter (0.5 to 1 cm) compared to the larger Tong Cao (Da Tong Cao, 大通草, 1 to 2.5 cm diameter). In market practice, Xiao Tong Cao has actually become the dominant commercial product, reportedly accounting for about 70% of the "Tong Cao" traded in herbal markets. Though it is considered slightly less potent than the true Tong Cao, it is more widely available and affordable. The Stachyurus genus name derives from the Greek for "spike flower," and the Chinese name "Jing Jie Hua" (旌节花) refers to the way the dangling flower spikes resemble ancient Chinese ceremonial staffs or pennants (旌节).

Modern Research

3 published studies investigating the pharmacological effects or clinical outcomes of Xiao Tong Cao

1

New Cytotoxic Steroid from Stachyurus himalaicus var. himalaicus (Phytochemical study, 2007)

Wang YS, Yang JH, Luo SD, Zhang HB, Li L. Molecules, 2007, 12(3), 536-542.

Researchers isolated a new steroid compound named stachsterol along with three known ecdysteroids (phytoecdysteroids found for the first time in this genus) from the ethanolic extract of S. himalaicus. The new steroid showed cytotoxic activity against human HeLa cell lines in vitro with an IC50 of 2.5 micrograms per millilitre. This was a preclinical laboratory study.

PubMed
2

Triterpenes from Stachyurus himalaicus var. himalaicus (Phytochemical study, 2010)

Wang YS, Huang R, Li NZ, Xu HY, Yang JH. Molecules, 2010, 15(4), 2096-2102.

Four triterpene compounds, including one new naturally occurring oleanane-type triterpene named stachlic acid C, were isolated from the leaves and twigs of S. himalaicus. Several compounds showed weak cytotoxic activity against HeLa cells. This was a preclinical phytochemical investigation.

3

New Polyoxygenated Triterpenoids from Stachyurus himalaicus var. himalaicus (Phytochemical study, 2006)

Yang JH, Wang YS, Huang R, Luo SD, Zhang HB, Li L. Helvetica Chimica Acta, 2006, 89, 2830-2835.

Two new polyoxygenated triterpenoids (stachlic acid A and stachlic acid B) were isolated from the plant. Stachlic acid A showed moderate cytotoxic activity against human HeLa cells in vitro. This was a preclinical phytochemical study elucidating the plant's chemical constituents.

Research on individual TCM herbs is growing but still limited by Western clinical trial standards. These studies provide emerging evidence and should be considered alongside practitioner expertise.