Couch grass

Couch Grass (Elymus repens)

1. Identity: Botanical Names, Natural Source, and Common Forms

1.1 Botanical and Chemical Identity

Elymus repens, commonly known as couch grass, is a very common perennial species of grass native to most of Europe, Asia, the Arctic, and northwest Africa. It is known by numerous common names in different languages and regions, including couch grass, quackgrass, wheatgrass, creeping quackgrass, twitch grass, dog grass, and various regional vernacular terms.

Synonyms include Agropyron repens (L.) Gould, Elytrigia repens (L.) Desv. ex Nevski, Elytrigia vaillantiana, Graminis rhizoma, Triticum repens, and Triticum vaillantianum Wulfen & Schreb. In the European Pharmacopoeia monograph (ref. 01/2008:1306), couch grass rhizome (Graminis rhizoma) is formally defined as the whole or cut, washed, and dried rhizome of Agropyron repens (L.) Beauv. (Elymus repens (L.) Gould), with adventitious roots removed.

E. repens is a plant native to temperate regions of the Euro-Mediterranean region, including Macaronesia, the Black Sea region, the Caucasus, Siberia, the Russian Far East, Central and Western Asia, as well as the Himalayas, China, Korea, and Mongolia. It has been brought into other mild northern climates for forage or erosion control, but is often considered a weed.

1.2 Morphology

It has flat, hairy leaves with upright flower spikes. The stems ("culms") grow to 40–150 centimetres tall; the leaves are linear, 15–40 centimetres long and 3–10 millimetres broad at the base of the plant. The grass also possesses shiny, pale yellow, hollow rhizomes and longitudinally grooved stems that are 2 to 3 mm thick. It has creeping rhizomes which enable it to grow rapidly across grassland.

1.3 Medicinal Part and Common Forms

The parts used medicinally are the rhizomes, roots, and stems. The part most commonly used is the rhizome (the underground stem), which is dried and prepared as tea, tincture, or standardized extracts. Preparations encountered in traditional and contemporary herbal practice include dried rhizome (for decoction and infusion), fluid extracts, tinctures, and encapsulated powders.

Chemical research on the plant is focused on its allelopathic and anti-inflammatory components, which are mainly present in the essential oil. Conversely, the aqueous extracts have been sparingly investigated, although the herbal tea is by far the most used formulation.

2. Traditional and Historical Use

2.1 Ancient Greek and Classical Medicine

Dioscorides and Galen directly referenced couch grass's use in ancient Greek medicine, particularly for bladder and kidney afflictions. The Greek physician Dioscorides mentioned its use for promoting urination and relieving obstruction.

2.2 Medieval and Renaissance European Herbalism

In medieval European herbalism, couch grass was prescribed for urinary gravel, kidney ailments, and as a general cleansing herb. It appeared in several canonical herbals and was associated with the kidney and bladder in humoral medical frameworks.

2.3 British Pharmaceutical and Eclectic Traditions

Formerly known as Agropyron repens, and Triticum repens prior to that, couch grass appeared in the British Pharmaceutical Codex 1911 as a "demulcent diuretic." Couch grass is accepted in the Indian and Colonial Addendum of the British Pharmacopoeia for use in the Australian, Eastern, and North American Colonies, where it is much employed.

In 19th-century Western herbalism, it was highly regarded by Eclectic physicians in the United States as a reliable diuretic and demulcent, particularly useful in catarrhal cystitis, chronic urethral irritation, and prostatitis. Herbalists used it to relieve burning urination, increase urine flow, and expel small kidney stones or gravel.

2.4 Use in Continental Europe

Daily dosing of couch grass rhizome in continental Europe, in the period from the 1950s to the 1990s, was at the dosage of 40 g and was lowered over time, to the dosage of 6–9 g daily, as a result of regulatory activity in Germany following the Commission E monograph.

In folk medicine, couch grass has been used as a diuretic in cases of bladder catarrh and bladder/kidney stones, and as a cough medicine to alleviate bronchial irritation.

2.5 Traditional Use in Other Cultures

In Greece, according to ethnobotanical tradition, couch grass is used not only in urinary tract disorders (cystitis, kidney stones, prostate enlargement) but also in gastrointestinal problems (gallstones), arthritis and rheumatism, and to reduce increased cholesterol levels. Ethnobotanical surveys have also documented traditional use of couch grass for kidney and urinary disorders in the cold desert Ladakh region of India, and in Iraqi traditional medicine.

3. Key Constituents and Active Compounds

3.1 Overview of the Chemical Profile

The bioactive compound composition of E. repens displays a variety of compounds including carbohydrates, phenolic acids, flavonoids, benzoxazinoids, and volatile compounds, all of which contribute to its medicinal properties.

3.2 Carbohydrates and Polysaccharides

The rhizome contains carbohydrates (approximately 10%), including triticin (3–8%), a polysaccharide related to inulin; inositol; mannitol; mucilage (approximately 10%); volatile oil (0.01–0.05%); flavonoids (including tricin); cyanogenic glycosides; saponins; vanilloside (vanillin monoglucoside); vanillin; and phenolcarboxylic acids.

Triticin is a fructan-type polysaccharide. Couch grass is stated to possess diuretic properties due in part to the presence of carbohydrates such as mannitol and inulin. Saponin and potassium content are both theorized to induce urinary flow by increasing the osmotic pressure within the glomerular tubules. Small sugars present are poorly absorbed from the gut and may also account for gentle diuretic effects.

3.3 Volatile Oil and Agropyrene

Agropyrene is the main volatile compound present in the volatile oils of couch grass. It is one of the main active principles, which has been demonstrated to have broad antibiotic activity in laboratory studies. Agropyrene (or hexa-2,4-diynylbenzene) constitutes approximately 95% of E. repens essential oils and has an antibiotic effect on fungi and bacteria.

However, a critical distinction must be made regarding certain compounds historically attributed to E. repens. Agropyrenol, agropyrenal, and agropyrenone were reported from a fungal pathogen associated with E. repens, not from the plant itself, and should therefore not be interpreted as endogenous medicinal constituents of E. repens. This clarification prevents misattribution of bioactivity and ensures that pharmaceutical development focuses on genuinely plant-derived compounds.

3.4 Phenolic Acids and Flavonoids

ESI-MS fingerprinting of the rhizome herbal tea has evidenced diagnostic ions for saccharides, organic acids, and amino acids. HPLC-PDA-ESI-MS/MS analysis identified at least 20 characteristic phenolic compounds, the most representative being caffeoyl and feruloyl quinic esters, followed by coumaric, caffeic, and ferulic acids, and hesperidin among flavonoids.

Additional flavonoids identified include rutin, hyperoside, and baicalein, and the rhizome also contains coumarins, iridoids, and phenocarboxylic acids such as chlorogenic and p-hydroxycinnamic acids.

3.5 Benzoxazinoids

The bioactive compound composition also includes benzoxazinoids, which contribute to the plant's medicinal properties. These are secondary metabolites also found in other cereal grasses and are associated with allelopathic and potentially antimicrobial effects.

3.6 Mucilage and Demulcent Compounds

Also present in the rhizome are mucilaginous substances (approximately 10%); saponins; sugar alcohols (mannitol and inositol, 2% to 3%); essential oil with polyacetylenes or carvone (0.01% to 0.05%); small amounts of vanilloside, vanillin, and phenolcarboxylic acids; silicic acid; silicates; and iron.

3.7 Proposed Mechanisms of Action

The pharmacological properties of E. repens are mainly facilitated by synergistic interactions among multiple phytochemical classes rather than a single major constituent. Phenolic acids and their derivatives influence antioxidant and anti-inflammatory effects through radical scavenging and enzyme modulation. Polyphenols and flavonoids appear responsible for enzyme inhibition relevant to antidiabetic activity. Saccharides, fructans, and mucilaginous compounds support soothing and demulcent effects on urinary mucosa. Volatile constituents and certain allelochemicals contribute antimicrobial and antiadhesive effects.

In the literature, the diuretic properties are attributed, although not supported by formal clinical data, to the presence of non-absorbable sugars such as mannitol, saponins, and vanillin, while the anti-inflammatory property is related to the presence of mucilage polysaccharides.

4. Scientific Evidence by Area of Use

4.1 Urinary Tract Infections (UTIs)

In vitro evidence: The rhizomes from Agropyron repens are traditionally used for the treatment of uncomplicated urinary tract infections. Extracts prepared with solvents of different polarity did not show any cytotoxic effects against different strains of uropathogenic E. coli (UPEC) and human T24 bladder cells under in vitro conditions. Significant antiadhesive activity against bacterial attachment to human T24 bladder cells was found for an acetone extract (AAE) at concentrations >250 μg/mL. More hydrophilic extracts did not influence the bacterial attachment to eukaryotic host cells. Bioassay-guided fractionation of AAE led to the identification of (E)-hexadecyl-3-(4-hydroxyphenyl)-acrylate (hexadecyl-coumaric acid ester) as the compound responsible for inhibiting UPEC adhesion to T24 bladder cells. This compound also reduced bacterial invasion into bladder cells.

Other constituents in couch grass have antiadhesive activity against urinary pathogens, inhibiting bacterial attachment to human bladder cells by interacting with the bacterial outer membrane. It should be noted that this antiadhesive activity has only been demonstrated in isolated human bladder epithelial cells in vitro, and more clinical research is needed.

Post-marketing surveillance (clinical observational study): A post-marketing surveillance study investigated the efficacy and tolerability of a fluid extract of Agropyron repens ("couch grass drops") in 133 patients with urinary tract infections or irritable bladder. For an average of twelve days, patients were administered 50–60 drops (~3 ml), three times per day.

Open clinical trial: In an open clinical trial in 99 patients with micturition disorders (12 female and 87 male), a 20% ethanol fluid extract of Agropyron repens was administered for 28–31 days. The complaints of urge incontinence, dysuria, nocturia, and tenesmus due to adenoma of the prostate, prostatitis, and cystitis were significantly reduced in 44.4–100% of patients. Laboratory markers of inflammation (protein, epithelia, leucocytes, and erythrocytes in urine) were also normalized. As a result, 96% of patients estimated results as "good" or "very good." Adverse effects were not recorded.

Limitations: As with so many traditional herbal remedies, there is minimal clinical evidence to support the use of couch grass. The indications are largely based on traditional use, in vitro research into the plant constituents, and in vivo animal studies. The open trial and post-marketing study cited above lack randomization, blinding, and placebo controls, significantly limiting their evidential weight.

4.2 Kidney Stones (Urolithiasis)

Animal study: In one study reporting on the effects of couch grass on calcium oxalate urolithiasis risk in rats, antilithiasic effects were dependent on diet.

Prospective randomized clinical study: Brardi et al. (2012), in a prospective randomized comparison study, investigated the effects of the combination of potassium citrate and Agropyron repens in renal stone treatment compared with potassium citrate alone. In an unblinded study, 50 participants were divided into two arms, the first 25 taking potassium citrate plus Agropyron repens combination and the other arm of 25 participants taking only potassium citrate. Both arms were advised to take the same diet and increased fluid intake over a 5-month follow-up period. There was a significant reduction in the total number of stones, stone diameter, and reduction in excreted uric acid in the combination arm compared with the potassium citrate-only group, without a significant difference in citraturia, oxaluria, urinary calcium, and urinary pH. This study concluded that using the combination of couch grass and potassium citrate was safe and effective compared with potassium citrate alone to treat urinary stones.

Pediatric study: A pediatric randomized controlled study (n = 50) on urinary stone disease revealed that E. repens extract dramatically decreased the quantity (88%) and size (92%) of renal calculi, while also improving renal colic, hematuria, and sepsis, without severe adverse effects. These effects were attributed mainly to increased urine flow, anti-inflammatory activity, antimicrobial support, and spasmolytic action.

Overall evidence strength: The biological potential underlines antiurolithiatic qualities with molecular insights showing synergistic interactions across many compound classes. The current reported data notably confirmed its potential in lowering renal calculi and alleviating associated symptoms; however, the findings remain limited. The Brardi (2012) trial was unblinded and enrolled only 50 participants, and the pediatric trial is preliminary.

4.3 Diuretic Activity

Diuretic activity was demonstrated by Racz-Kotilla and Mozes (1971) in rats, after oral administration of an aqueous extract (1% macerate). Couch grass has demonstrated diuretic and sedative activities in rats and mice. No large-scale human RCTs specifically examining the diuretic effect of couch grass as a primary endpoint have been identified in the literature.

4.4 Anti-Inflammatory Activity

An alcoholic extract of couch grass has demonstrated anti-inflammatory properties, being able to induce a weak inhibition of inflammation induced by carrageenan in animal models. Rhizomes of A. repens demonstrated in vitro inhibitory activity against markers of inflammation in a screening study of 71 Austrian traditional herbal drugs. Evidence for anti-inflammatory effects in humans remains absent from the published literature.

4.5 Antidiabetic and Hypoglycemic Activity

The traditional medicinal use in urinary calculus disease has received scientific confirmation, including for other pharmacological effects. Among the pharmacological actions documented in the literature are hypoglycemic, hypolipidemic, anti-inflammatory, and antidiabetic activities, effects on motility, and beneficial effects in urinary tract infections. In general, clinical studies are lacking to support traditional uses of couch grass. Animal studies suggest potential benefit in diabetes and in the treatment of urinary tract conditions (urolithiasis and infection). However, due to the lack of clinical data, couch grass cannot be recommended for any indication.

Polyphenols and flavonoids appear responsible for enzyme inhibition relevant to antidiabetic activity, but all evidence supporting antidiabetic effects derives from preclinical (animal and in vitro) experiments. No human trials on this indication have been reported.

4.6 Antimicrobial Activity

The chemical constituent agropyrene has been shown to have strong antibiotic properties. This finding derives from in vitro studies. A. repens extracts demonstrated no direct bactericidal activity against uropathogenic E. coli organisms; however, antiadhesive activity against bacterial attachment to bladder cells was reported.

4.7 Regulatory Recognition: EMA/HMPC Traditional Use Status

The available data are sufficient to establish a Community herbal monograph on the traditional use of couch grass rhizome. Couch grass rhizome fulfills the requirement of medicinal use for at least 30 years (including at least 15 years within the European Union, Directive 2004/24/EC). The approved indication is: "Traditional herbal medicinal product to increase the amount of urine to achieve flushing of the urinary tract as an adjuvant in minor urinary complaints." The product is a traditional herbal medicinal product for use in the specified indication exclusively based upon long-standing use.

The German Commission E approved couch grass for irrigation therapy. Commission E, as documented by Blumenthal et al. (1998), approves 6–9 g of dry quackgrass per day for "irrigation therapy for inflammatory diseases of the urinary tract and for the prevention of kidney gravel."

5. Body Systems and Health Areas

Based on the documented traditional use and available scientific literature, couch grass is associated with the following body systems and health areas:

• Urinary system: Actions include diuretic, demulcent, and anti-microbial effects; medical uses include urinary infections such as cystitis, urethritis, and prostatitis.
• Renal system: It can be used for UTIs, kidney gravel and stones, and benign prostatic hyperplasia (BPH).
• Musculoskeletal system: In Greek ethnobotanical tradition, couch grass has been employed for arthritis and rheumatism, though scientific evidence for this use is absent.
• Respiratory system: Couch grass exhibits soothing, anti-inflammatory effects that have been traditionally considered beneficial for respiratory health. It has been used to ease conditions such as bronchitis and other inflammatory respiratory issues. Evidence here is purely traditional.
• Metabolic/endocrine system: Preclinical evidence suggests possible hypoglycemic and hypolipidemic effects, though no human data exist.
• Immune/inflammatory system: Phenolic acids and their derivatives influence antioxidant and anti-inflammatory effects through radical scavenging and enzyme modulation, based on in vitro data.

6. Dosage Forms and Reported Dosages

The following dosages have been reported in the scientific and regulatory literature. These are descriptive of what has been used or studied, not prescriptive recommendations.

• Dried rhizome (herbal tea/decoction): Traditional doses of the rhizome were 6 to 10 g daily for suspected urinary tract infections, as cited in Blumenthal (2000), Duke (2002), and EMA (2011). In the British tradition, for the entire period of 30 years, the daily dose was 24 g. In the first edition of the HMPC monograph, the daily dosage was established at a level of 10–20 g of herbal substance.
• Liquid (fluid) extract: As a liquid (1:1 in 25% alcohol) extract, 4–8 milliliters three times per day has been used.
• Tincture: As a tincture (1:5 in 40% alcohol), 5–15 milliliters three times per day has been used.
• Fluid extract in clinical study (post-marketing surveillance): A fluid extract of Agropyron repens was administered at 50–60 drops (~3 ml) three times per day for an average of twelve days in 133 patients with urinary tract infections or irritable bladder.
• 20% ethanol fluid extract (open clinical trial): A 20% ethanol fluid extract of Agropyron repens was administered for 28–31 days in an open clinical trial in 99 patients with micturition disorders.
• Dry extract in combination (renal stone trial): In the Brardi prospective randomized trial, a dry extract of couch grass 100 mg substantially reduced the total number of stones compared to the potassium citrate group.
• Registered liquid extract in Germany: The liquid extract (DER 1:1), prepared with 20% V/V ethanol, was reported to be registered in Germany with the posology of a single dose of 3 ml, used 3 times daily.

There is no proven safe or effective dose for couch grass in adults that is established by high-quality clinical trials. Traditionally, 4–8 grams of dried rhizome has been taken three times daily.

7. Safety Considerations and Interactions

7.1 General Safety Profile

There are no available systematic non-clinical safety data. Couch grass rhizome was well known for its traditional use in folk medicines across Europe and outside from times when animal tests were not required. Couch grass rhizome fulfills the requirement of medicinal use for at least 30 years. Due to the lack of data on acute and chronic toxicity, repeated dose toxicity, carcinogenicity, reproductive and developmental toxicity, the EMA's assessment of the herb relies on traditional use rather than formal toxicological characterization.

There are no known adverse effects associated with use of couch grass, although the potential for allergy exists. No data regarding toxicology are available.

7.2 Allergy Risk

Interference with laboratory tests is theoretically possible because couch grass leaf lectin exhibits specificity for N-acetylgalactosamine and preferentially agglutinates blood group A erythrocytes. As a member of the grass family, the potential for allergy exists. Individuals with known grass allergies should be aware of this consideration.

7.3 Electrolyte Imbalance

Excessive and prolonged use of couch grass should be avoided due to its reputed diuretic action, as this may result in hypokalemia (abnormally low potassium levels in the blood).

7.4 Edema Arising from Cardiac or Renal Disease

Caution is advised in patients who have edema caused by heart or kidney disease. Based on tradition, couch grass should be taken with plenty of fluids to flush out the urinary tract.

7.5 Pregnancy and Lactation

Couch grass is not recommended in pregnant or breastfeeding women due to lack of available scientific evidence.

7.6 Drug Interactions

No drug interactions are well documented for couch grass. Those on medication for blood pressure or diuretics should exercise caution, as couch grass can potentially amplify the effects of these drugs, leading to electrolyte imbalances. This theoretical interaction has not been confirmed in clinical pharmacokinetic studies.

7.7 Summary of Evidence Strength

There is minimal clinical evidence to support the use of couch grass for any indication. The indications are largely based on traditional use, in vitro research into the plant constituents, and in vivo animal studies. The single best-controlled clinical trial is the unblinded, small-enrollment Brardi (2012) study on urolithiasis, which found benefit in combination with potassium citrate but has significant methodological limitations. The EMA/HMPC has granted a traditional use registration only, not a full evidence-based medical indication. In general, clinical studies are lacking to support traditional uses of couch grass. Animal studies suggest potential benefit in diabetes and in the treatment of urinary tract conditions. However, due to the lack of clinical data, couch grass cannot be recommended for any indication.

References

• Elymus repens (L.) Gould Phytochemistry Pharmacological Activities and Therapeutic Potential with Future Perspectives — International Journal of Molecular Sciences (PubMed / MDPI, 2025)
• Elymus repens (L.) Gould Phytochemistry Pharmacological Activities and Therapeutic Potential with Future Perspectives — PubMed abstract
• Metabolic Profile of Agropyron repens (L.) P. Beauv. Rhizome Herbal Tea by HPLC-PDA-ESI-MS/MS Analysis — PMC / Molecules (2022)
• Assessment Report on Agropyron repens (L.) P. Beauv., Rhizoma (Revision 1) — European Medicines Agency / HMPC
• Assessment Report on Agropyron repens (L.) P. Beauv., Rhizoma (original) — European Medicines Agency
• Traditionally used medicinal plants against uncomplicated urinary tract infections: Hexadecyl coumaric acid ester from Agropyron repens with antiadhesive activity against uropathogenic E. coli — Fitoterapia / PubMed (Beydokthi et al., 2017)
• Effects of the association of potassium citrate and Agropyrum repens in renal stone treatment — Arch Ital Urol Androl (Brardi et al., 2012) — ResearchGate
• Phytotherapy in Urolithiasis: An Updated Overview of Current Knowledge — Journal of Clinical Medicine / MDPI (2025)
• Couch Grass Uses, Benefits & Dosage — Drugs.com (Natural Products Database, medically reviewed 2025)
• Couch Grass (Elymus repens): Benefits, Safety, Research — Herbal Reality (2026)
• Elymus repens — Wikipedia
• Traditionally used medicinal plants against uncomplicated UTIs: Hexadecyl coumaric acid ester (Beydokthi et al.) — ScienceDirect / Fitoterapia (2017)
• Dietary Plants for the Prevention and Management of Kidney Stones: Preclinical and Clinical Evidence — Int. J. Mol. Sci. / MDPI (2018)