Zi Su Geng 紫苏梗 — Chinese Herbal Medicine

Zi Su Geng (紫苏梗) At a Glance

• Herb: Zi Su Geng
• Chinese name: 紫苏梗 (Zi Su Geng)
• Latin name: Caulis Perillae
• Nature: Warm
• Taste: Acrid
• Meridian: Lung
• Category: Regulate the qi

Zi Su Geng (紫苏梗, Caulis Perillae) is the dried stem of Perilla frutescens (L.) Britt. (Lamiaceae), harvested in autumn when the fruit has ripened. While Zi Su Ye (the leaf) excels at releasing the exterior and stopping vomiting, Zi Su Geng (the stem) is specifically valued for regulating Qi, harmonising the Middle Jiao, and calming the restless fetus. The distinction between leaf and stem is classic TCM phytopharmacology: the leaf, being light and upward-moving, addresses the exterior; the stem, being heavier and more interior-directed, moves Qi through the Middle Jiao and channels. In pregnancy, Zi Su Geng is often preferred over the leaf when the primary issue is Qi stagnation threatening fetal stability rather than exterior invasion or overt vomiting. Its acrid-warm character allows it to move Qi without the sharp, drying harshness of stronger Qi-regulating herbs, making it suitable for relatively delicate conditions.

Actions & Therapeutic Effects

• Regulates Qi and harmonises the Middle Jiao — treats epigastric and abdominal distension, belching, and digestive Qi stagnation, especially when accompanied by a sensation of fullness and oppression.
• Calms the restless fetus (安胎) — treats threatened miscarriage (胎动不安) from Qi stagnation with fullness and discomfort in the lower abdomen.
• Moves Qi in the chest and diaphragm — relieves chest oppression and discomfort from Qi stagnation in the chest and upper epigastrium.
• Resolves the toxicity of fish and crab — milder than the leaf but retains some detoxifying action for seafood poisoning.

Clinical Applications in TCM

• Qi stagnation during pregnancy with abdominal distension and threatened miscarriage — combined with Sha Ren and Bai Zhu
• Epigastric fullness and belching from Spleen-Stomach Qi stagnation — paired with Chen Pi and Mu Xiang
• Morning sickness with Qi stagnation (distension more prominent than vomiting) — used with Zi Su Ye and Sheng Jiang
• Chest oppression from Qi and Phlegm obstruction — combined with Zhi Qiao and Jie Geng
• Postoperative abdominal distension from Qi stasis — used with Hou Po and Da Fu Pi
• Hiccough from Cold-Qi stagnation — Zi Su Geng decoction alone or with Ding Xiang

Precautions & Safety

• Dosage: 5–10 g in decoction
• Contraindicated in Qi deficiency without stagnation — its Qi-moving nature may further deplete
• Generally safe during pregnancy for appropriate patterns (Qi stagnation threatening the fetus)
• Avoid in patients with profuse sweating or exterior deficiency
• The stem is milder than the leaf for exterior-releasing action — do not substitute Su Geng for Su Ye when exterior symptoms are the primary concern
• Can be combined with Su Ye when both Qi stagnation and exterior symptoms are present

Classical TCM Formulas

• Tai Shan Pan Shi San (泰山磐石散): Ren Shen, Huang Qi, Dang Gui, Xu Duan, Huang Qin, Bai Zhu, Chuan Xiong, Bai Shao, Shu Di Huang, Sha Ren, Zhi Gan Cao, Nuo Mi — the premier pregnancy-stabilising formula; Zi Su Geng is often added for Qi stagnation variants.
• Zi Su Yin (紫苏饮): Zi Su, Da Fu Pi, Dong Gua Pi, Sang Bai Pi — promotes urination and reduces oedema in pregnancy with Qi stagnation and fluid retention. Source: Fu Ren Da Quan Liang Fang.
• Xiang Su San (香苏散) + Zi Su Geng: Xiang Fu, Zi Su Ye, Chen Pi, Gan Cao + Su Geng — releases exterior and more strongly regulates Qi for colds with prominent Qi stagnation symptoms.

Herb Combinations

• Zi Su Geng + Sha Ren (砂仁) + Bai Zhu (白术): the pregnancy Qi-regulating triad — Su Geng moves Qi, Sha Ren awakens the Spleen, Bai Zhu secures the fetus. Source: Classical pregnancy formulas.
• Zi Su Geng + Chen Pi (陈皮) + Mu Xiang (木香): regulates Qi and awakens the Spleen for abdominal distension and dyspepsia.
• Zi Su Geng + Hou Po (厚朴) + Da Fu Pi (大腹皮): moves Qi and disperses abdominal fullness — effective for distension from Dampness and Qi stagnation.
• Zi Su Geng + Dang Shen (党参) + Fu Ling (茯苓): moves Qi while protecting Spleen Qi — the standard balanced approach for Qi stagnation with deficiency.
• Zi Su Geng + Zhu Ru (竹茹) + Huang Qin (黄芩): for pregnancy Qi stagnation with mild Heat signs — the cool herbs balance the acrid-warm stem.

Pharmacology & Research

Gastrointestinal prokinetic: perillaldehyde and rosmarinic acid promote gastric emptying and enhance intestinal transit — the biochemical basis for the ‘regulates Qi’ action.
Antispasmodic: volatile oil components relax gastrointestinal smooth muscle, reducing intestinal cramping and distension.
Mild uterine relaxant: rosmarinic acid demonstrates tocolytic activity in isolated uterine strips, supporting the traditional ‘calms the fetus’ indication.
Antioxidant: rosmarinic acid and luteolin derivatives provide significant free-radical scavenging activity.
Antimicrobial: perillaldehyde demonstrates broad-spectrum antibacterial activity, especially against oral and gastrointestinal pathogens.

Classical Descriptions

• 《本草纲目》(Bencao Gangmu, 1596) — Li Shizhen: “苏茎叶，下气消谷，除寒中，补虚，通大小肠，安胎。” (Perilla stem and leaf: descends Qi and disperses grain [stagnation], eliminates Cold in the Middle, supplements vacuity, unblocks the large and small intestines, calms the fetus.)
• 《本草备要》(Bencao Beiyao, 1694) — Wang Ang: “苏梗，顺气安胎。” (Su Geng: smooths the Qi and calms the fetus.)
• 《本草正义》(Bencao Zhengyi, 1920) — Zhang Shanlei: “苏叶偏于发散风寒，苏梗偏于理气宽中。” (Su Ye is biased toward dispersing Wind-Cold; Su Geng is biased toward regulating Qi and loosening the Middle.)