✵The article records the herb Rhubarb, including its English name, Latin name, Pinyin Name, properties and flavors, and its botanical sources—three plant species: (1) Rheum palmatum L., (2) Rheum tanguticum Maxim. ex Balf., and (3) Rheum officinale Baill. It provides a detailed introduction to the botanical features, growth characteristics, and ecological environments of these three plants; the characteristics of the herb Rhubarb; its pharmacological actions, medicinal efficacy, and administration guidelines.
Radix et Rhizoma Rhei (Rhubarb)
Pinyin Name: Dà Huánɡ
English Name: Rhubarb
Latin Name:Radix et Rhizoma Rhei Property and Flavor: Cold in nature; bitter in taste.
Brief Introduction:Radix et Rhizoma Rhei is the dried root and rhizome of Rheum palmatum L., Rheum tanguticum Maxim. ex Balf., or Rheum officinale Baill. It is used to induce catharsis, clear heat, purge fire, stop bleeding, counteract toxins, and remove blood stasis. It is indicated for: (1) constipation due to gastrointestinal accumulation; (2) warm diseases with high fever, delirium, and constipation; (3) postpartum abdominal pain and amenorrhea due to blood stasis; (4) hemoptysis, hematemesis, and epistaxis associated with excessive heat in the blood; and, externally, (5) burns, boils, and sores. The herb is commonly known as Radix et Rhizoma Rhei, Rhubarb, or Dà Huáng.
Botanical Source: Common classical herbal works and other authoritative herbal compendia define Rhubarb (Da Huang) as the dried root and rhizome of the following plant species: (1) Rheum palmatum L., (2) Rheum tanguticum Maxim. ex Balf., or (3) Rheum officinale Baill. These are species of the genus Rheum L. in the family Polygonaceae (smartweed or buckwheat family), order Caryophyllales (formerly in the order Polygonales). These three commonly used species are described below:
(1) Rheum palmatum L.
Botanical Description:Rheum palmatum L. is a perennial herb of the Polygonaceae family (smartweed or buckwheat family) and the genus Rheum. It is commonly known as Palmar-leaved Rheum or Zhǎng Yè Dà Huáng (meaning "palmate-leaf Da Huang"). The plant grows upright to a height of about 2 meters; its stems are hollow, smooth, and glabrous. The roots and rhizomes are stout, hypertrophic, and slightly lignified; the outer bark is dark brown, and the cross-section is dark yellow with vascular bundles arranged in a ring around the periphery of the rhizome.
Basal leaves are large, with stout, succulent, and elongated petioles approximately equal in length to the leaf blades. Leaf blades are broadly cordate or suborbicular, up to 35 cm in diameter—or over 40 cm in some cases—and palmately 3–7-lobed; each lobe is often further pinnately divided. The upper surface is sparsely papillate, while the lower surface is pilose. Cauline leaves are smaller and bear shorter petioles. Ocreae (stipular sheaths) are terete and densely pubescent.
Inflorescences are large, conical, and terminal, measuring 10–20 cm in length. Pedicels are slender and elongated, with nodes present in their middle and lower portions. Flowers are small, violet-red (prunus) or purplish, borne in clusters. Each flower has 6 tepals (~1.5 mm long), arranged in two whorls; 9 stamens, slightly exserted beyond the perianth; and 3 styles.
Achenes are trigonous, with three prominent ridges; wings develop along the ridges. The apex is slightly emarginate, and the base is nearly cordate. The fruit is dark brown (dust-colored). Flowering occurs from June to July; fruiting from July to August.
Ecological Environment: Rheum palmatum grows in mountainous regions, forest margins, grassy slopes, valley wetlands, hillsides, and alpine grasslands, at altitudes of 1,500–4,400 m above sea level. It is also cultivated.
Growth Characteristics:Rheum palmatum L. prefers cool to cold climates and is highly cold-tolerant but sensitive to high temperatures. It grows wild in alpine zones at ~2,000 m elevation and is typically cultivated at 1,400 m. Winter minimum temperatures fall below –10 °C (14 °F), and summer maximum temperatures remain below 30 °C (86 °F). The frost-free period lasts 150–180 days, and annual precipitation ranges from 500–1,000 mm. Soil requirements are strict: deep, humus-rich loam or well-drained sandy loam is ideal; heavy acidic soils and low-lying, waterlogged sites are unsuitable. Continuous cropping must be avoided; rotation intervals of 4–5 years are recommended.
(2) Rheum tanguticum Maxim. ex Balf.
Botanical Description:Rheum tanguticum Maxim. ex Balf. is a tall perennial herb of the Polygonaceae family and the genus Rheum. It is commonly known as Chicken-toed Rheum, Táng Gū Tè Dà Huáng, or Jī Zhǎo Dà Huáng (meaning “chicken-toed Da Huang”). Plants reach 1.5–2 m in height. Roots and rhizomes are stout and yellow. Stems are thick, hollow, longitudinally ridged, smooth and glabrous—or bearing rough, short hairs at the nodes of the upper portion.
Cauline leaves are large; leaf blades are suborbicular or broadly ovate, 30–60 cm long, with a narrow, elongated, acuminate apex and a slightly cordate base. They are usually palmately 5-lobed: the basal pair of lobes is simple, whereas the three central lobes are mostly tripinnatipartite. Lobules are narrowly lanceolate, with five basal veins. The upper leaf surface is papillate or scabrous; the lower surface bears dense, short hairs. Petioles are subcylindrical and nearly as long as the leaf blades, covered with rough, short hairs. Upper cauline leaves are smaller, with shorter petioles and more numerous, narrower lobes. Ocreae are large, often fragmented laterally, and pubescent externally.
Inflorescences are large panicles with densely clustered branches. Flowers are small, violet-red (prunus), rarely pale red. Pedicels are filiform, 2–3 mm long, with nodes located in the lower portion. Tepals are nearly elliptic; the inner whorl is larger, ~1.5 mm long. Stamens number nine and are not exserted. The floral disc is thin, adnate to the base of the filaments, forming a shallow, cup-like structure. The ovary is broadly ovate; the style is short and explanate; the stigma is capitate.
Fruits are rectangular-circular to oval, with a rounded or truncate apex and a slightly cordate base, measuring 8–9.5 mm in length and 7–7.5 mm in width. Wings are 2–2.5 mm wide, with vertical veins near their margins. Seeds are ovoid and dark brown (nearly black). Flowering occurs in June; fruiting, from July to August.
The morphological characteristics of this species are extremely similar to those of Rheum palmatum L.; the main differences are as follows: leaves are deeply lobed; lobes are often triangular-lanceolate or narrowly linear; and lobes are narrow and elongated. The inflorescence branches are closely spaced, dense, erect, and tightly appressed to the stem.
Ecological Environment: The plant grows in alpine valleys at altitudes of 1,600–3,000 m above sea level—under mountain shrubbery or along forest margins—and in damp habitats.
The plant prefers a cool, dry climate and is cold-tolerant. It is prone to rot under conditions of high temperature and high humidity. Cultivation should be carried out in deep, well-drained sandy soil. Neutral to slightly alkaline soils are suitable. Rhubarb exhibits strong vitality; seed viability can be maintained for 3–4 years. Rosettes (leaf clusters) form only in the second year after sowing. The plant greens up in early April; flowering occurs in May and June of the third year, and fruit maturation spans June to October.
(3) Rheum officinale Baill.
Botanical Description:Rheum officinale Baill. is a tall perennial herb of the Polygonaceae family (smartweed or buckwheat family) and the genus Rheum. It is commonly known as Rheum officinale or Dà Huáng. Stems are erect, reaching 1.5–2 m in height. Roots and rhizomes are stout and yellow internally. Stems are robust, with a basal diameter of 2–4 cm; they are hollow, longitudinally grooved, and covered with short white hairs—denser on the upper portion and at the nodes.
Basal leaves are large; leaf blades are suborbicular (rarely broadly oval), 30–50 cm in diameter—or slightly longer than broad—with an acuminate apex and a subcordate base. They are palmately lobed; lobes are large, dentate, and triangular, with 5–7 basal veins. The upper leaf surface is smooth and glabrous, occasionally bearing sparse short hairs along the veins; the lower surface bears pale brown (hazel) short hairs. Petioles are thick and cylindrical, equal in length to or slightly shorter than the leaf blades, longitudinally ridged, and covered with short hairs. Cauline leaves gradually decrease in size upward; inflorescence branches arise from the upper leaf axils. Ocreae (stipular sheaths) are broad and large—up to 15 cm long—amplexicaul (stem-clasping) when young, later splitting; their inner surface is smooth and glabrous, while the outer surface is densely pubescent.
Inflorescences are large panicles with spreading branches. Flowers are borne in tufts of 4–10, greenish to yellowish-white. Pedicels are slender and elongated (3–3.5 mm long), with nodes located in their middle and lower portions. There are 6 tepals (perianth lobes); inner and outer whorls are nearly equal in size—elliptic or slightly narrowed elliptic—measuring 2–2.5 mm in length and 1.2–1.5 mm in width; margins are slightly undulate. There are 9 stamens, not exserted. The floral disc is thin and valviform. The ovary is ovoid or ellipsoidal; the style is retroflexed; the stigma is sphaerocephalous.
Fruits are oblong-elliptic, 8–10 mm long and 7–9 mm wide, with a rounded apex, a shallowly concave central region, and a shallowly cordate base. Wings are ~3 mm wide, with vertical veins approaching the wing margins. Seeds are broadly ovate. Flowering occurs from May to June; fruiting, from August to September.
Ecological Environment: The plant grows along mountainous forest margins or on grassy slopes, preferring moist, sunny habitats with deep, well-drained soils—both wild and cultivated.
Characteristics of the Herb: The dried root and rhizome are cylindrical, conical, fusiform (spindle-shaped), ovoid, or irregularly block-like—3–17 cm long and 3–10 cm in diameter. When the periderm is removed, the surface is yellowish-brown to reddish-brown, exhibiting off-white reticulated patterns and scattered “star dots” (heteromorphic vascular bundles). In specimens retaining the periderm, the surface is brown, marked by transverse wrinkles and longitudinal grooves; the apical portion bears a remnant of the cauline leaf base. The cross-section is typically uneven and non-planar. The texture is firm and compact; some specimens are slightly soft centrally and difficult to break. The fracture surface is light reddish-brown or yellowish-brown and granular. The rhizome medulla is broad, with star dots arranged in concentric rings or scattered. The xylem of the root is well-developed, showing prominent radial patterns; the cambium ring is inconspicuous and lacks star dots. The herb has a delicate fragrance, a bitter and slightly astringent taste, a mucilaginous (slightly sticky) sensation when chewed, and a faint gritty (sandy) feel.
Pharmacological Actions: (1) Purgative effect; (2) Antibacterial activity against both Gram-positive and Gram-negative bacteria—including Staphylococcus aureus, Streptococcus spp., Corynebacterium diphtheriae, Bacillus subtilis, Bacillus anthracis, Salmonella typhi, Salmonella paratyphi, and Shigella spp.; (3) Antitumor effects against melanoma, breast cancer, and ascites carcinoma in murine models.
Medicinal Efficacy: Inducing purgation and resolving accumulation, breaking stagnation and stasis, clearing heat and purging fire, clearing dampness and heat, purging toxic heat, draining pathogenic fire, cooling the blood and detoxifying, removing blood stasis and restoring menstrual flow, activating blood circulation to resolve stasis, promoting diuresis to eliminate dampness and resolving jaundice, dispelling phlegm, and detoxifying. It is indicated for excessive heat-induced indigestion and constipation; dyspepsia and abdominal distension and fullness (due to food retention); blood-heat-induced hematemesis or epistaxis; hematemesis (spitting blood); epistaxis (nosebleed, bleeding from the five orifices, or subcutaneous tissue); red eye (acute conjunctivitis); swelling and pain in the throat; oral and lingual ulcers; stomach-heat-induced nausea and vomiting; ocular swelling and pain; abdominal pain and intestinal abscess; blood stasis-induced amenorrhea; postpartum blood stasis obstruction; abdominal masses and lumps; traumatic injuries from falls; damp-heat dysentery; onset of dysentery; rectal tenesmus; jaundice and dark-red urine; stranguria; edema; edema with abdominal distension and fullness; turbid urinary discharge; difficulty in urination; delirium (delirious speech, incoherent talking); seasonal epidemic febrile diseases; yang-type jaundice; erysipelas (an inflammatory skin condition characterized by redness and swelling); large carbuncles and pyogenic infections; carbuncle swelling; and malignant boils. Externally, it is used for scalds and burns.
Wine-processed Rhubarb excels at clearing toxic heat from the upper jiao and is indicated for red eye, pharyngeal swelling, and gingival swelling. Prepared Rhubarb has a milder purgative effect, effectively clearing fire and detoxifying, and is indicated for carbuncles and ulcers caused by exuberant fire. Charred Rhubarb functions to cool the blood, resolve blood stasis, and arrest bleeding, and is indicated for bleeding syndromes due to blood-heat stasis, among others.
Administration of Radix et Rhizoma Rhei (Dà Huánɡ):
Reference:
Administration Guide for Radix et Rhizoma Rhei (Dà Huánɡ)
TCM Books:
(1) Internally: 3–15 grams; for purgative effect, avoid prolonged decoction. Externally: appropriate amount; prepare as finely ground herb powder and apply topically to the affected area. (2) Internally: water decoction, 1–4 qian (≈ 3–12 grams); avoid prolonged decoction for purgative effect; or formulate as pills or powders. Externally: prepare as finely ground herb powder, mix with water or vinegar, and apply topically. (3) Internally: water decoction, 3–12 grams; avoid prolonged decoction for purgative effect; or brew with boiling water and extract the juice; or use finely ground herb powder (0.5–2 g); or formulate as pills or powders. Externally: appropriate amount; prepare as finely ground herb powder for topical application (paste or wash), or apply as a smear after mixing with water decoction.
Contraindications, Precautions, and Adverse Reactions: Radix et Rhizoma Rhei should be used with caution during pregnancy, menstruation, lactation, and the pre- and postpartum periods. It should not be combined with Resina Toxicodendri.
✵The article records the herb Rhubarb, including its English name, Latin name, Pinyin Name, properties and flavors, and its botanical sources—three plant species: (1) Rheum palmatum L., (2) Rheum tanguticum Maxim. ex Balf., and (3) Rheum officinale Baill. It provides a detailed introduction to the botanical features, growth characteristics, and ecological environments of these three plants; the characteristics of the herb Rhubarb; its pharmacological actions, medicinal efficacy, and administration guidelines.
Pinyin Name: Dà Huánɡ
Botanical Description: Rheum palmatum L. is a perennial herb of the Polygonaceae family (smartweed or buckwheat family) and the genus Rheum. It is commonly known as Palmar-leaved Rheum or Zhǎng Yè Dà Huáng (meaning "palmate-leaf Da Huang"). The plant grows upright to a height of about 2 meters; its stems are hollow, smooth, and glabrous. The roots and rhizomes are stout, hypertrophic, and slightly lignified; the outer bark is dark brown, and the cross-section is dark yellow with vascular bundles arranged in a ring around the periphery of the rhizome.
Basal leaves are large, with stout, succulent, and elongated petioles approximately equal in length to the leaf blades. Leaf blades are broadly cordate or suborbicular, up to 35 cm in diameter—or over 40 cm in some cases—and palmately 3–7-lobed; each lobe is often further pinnately divided. The upper surface is sparsely papillate, while the lower surface is pilose. Cauline leaves are smaller and bear shorter petioles. Ocreae (stipular sheaths) are terete and densely pubescent.
Ecological Environment: Rheum palmatum grows in mountainous regions, forest margins, grassy slopes, valley wetlands, hillsides, and alpine grasslands, at altitudes of 1,500–4,400 m above sea level. It is also cultivated.
Growth Characteristics: Rheum palmatum L. prefers cool to cold climates and is highly cold-tolerant but sensitive to high temperatures. It grows wild in alpine zones at ~2,000 m elevation and is typically cultivated at 1,400 m. Winter minimum temperatures fall below –10 °C (14 °F), and summer maximum temperatures remain below 30 °C (86 °F). The frost-free period lasts 150–180 days, and annual precipitation ranges from 500–1,000 mm. Soil requirements are strict: deep, humus-rich loam or well-drained sandy loam is ideal; heavy acidic soils and low-lying, waterlogged sites are unsuitable. Continuous cropping must be avoided; rotation intervals of 4–5 years are recommended.
Botanical Description: Rheum tanguticum Maxim. ex Balf. is a tall perennial herb of the Polygonaceae family and the genus Rheum. It is commonly known as Chicken-toed Rheum, Táng Gū Tè Dà Huáng, or Jī Zhǎo Dà Huáng (meaning “chicken-toed Da Huang”). Plants reach 1.5–2 m in height. Roots and rhizomes are stout and yellow. Stems are thick, hollow, longitudinally ridged, smooth and glabrous—or bearing rough, short hairs at the nodes of the upper portion.
Cauline leaves are large; leaf blades are suborbicular or broadly ovate, 30–60 cm long, with a narrow, elongated, acuminate apex and a slightly cordate base. They are usually palmately 5-lobed: the basal pair of lobes is simple, whereas the three central lobes are mostly tripinnatipartite. Lobules are narrowly lanceolate, with five basal veins. The upper leaf surface is papillate or scabrous; the lower surface bears dense, short hairs. Petioles are subcylindrical and nearly as long as the leaf blades, covered with rough, short hairs. Upper cauline leaves are smaller, with shorter petioles and more numerous, narrower lobes. Ocreae are large, often fragmented laterally, and pubescent externally.
Ecological Environment: The plant grows in alpine valleys at altitudes of 1,600–3,000 m above sea level—under mountain shrubbery or along forest margins—and in damp habitats.
Botanical Description: Rheum officinale Baill. is a tall perennial herb of the Polygonaceae family (smartweed or buckwheat family) and the genus Rheum. It is commonly known as Rheum officinale or Dà Huáng. Stems are erect, reaching 1.5–2 m in height. Roots and rhizomes are stout and yellow internally. Stems are robust, with a basal diameter of 2–4 cm; they are hollow, longitudinally grooved, and covered with short white hairs—denser on the upper portion and at the nodes.
Ecological Environment: The plant grows along mountainous forest margins or on grassy slopes, preferring moist, sunny habitats with deep, well-drained soils—both wild and cultivated.
Characteristics of the Herb: The dried root and rhizome are cylindrical, conical, fusiform (spindle-shaped), ovoid, or irregularly block-like—3–17 cm long and 3–10 cm in diameter. When the periderm is removed, the surface is yellowish-brown to reddish-brown, exhibiting off-white reticulated patterns and scattered “star dots” (heteromorphic vascular bundles). In specimens retaining the periderm, the surface is brown, marked by transverse wrinkles and longitudinal grooves; the apical portion bears a remnant of the cauline leaf base. The cross-section is typically uneven and non-planar. The texture is firm and compact; some specimens are slightly soft centrally and difficult to break. The fracture surface is light reddish-brown or yellowish-brown and granular. The rhizome medulla is broad, with star dots arranged in concentric rings or scattered. The xylem of the root is well-developed, showing prominent radial patterns; the cambium ring is inconspicuous and lacks star dots. The herb has a delicate fragrance, a bitter and slightly astringent taste, a mucilaginous (slightly sticky) sensation when chewed, and a faint gritty (sandy) feel.
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