Hartstongue (Asplenium scolopendrium L.): A Comprehensive Reference
1. Identity: Botanical Classification, Names, and Natural Source
1.1 Accepted Botanical Name and Synonymy
Asplenium scolopendrium, commonly known as the hart's-tongue fern, is an evergreen fern in the family Aspleniaceae, native to the Northern Hemisphere. As a dietary supplement and herbal medicine, the plant is most frequently sold and referenced under the common names hartstongue, hart's-tongue, hart's-tongue fern, and spleenwort. Multiple synonyms have been applied to it over the centuries of taxonomic history. Its principal synonyms include Phyllitis japonica Kom., Phyllitis scolopendrium (L.) Newman, Scolopendrium scolopendrium H.Karst., and Scolopendrium vulgare Sm. Other historically used names documented in the herbal tradition include Lingua cervina (Latin for "tongue of a deer"), Scolopendrium officinale, and Scolopendrium vulgaris. In various languages and traditions it is also known as Buttonhole, God's-Hair, Hind's Tongue, Horse Tongue, Langue de Cerf, Lengua Cervina, and Scolopendre.
Linnaeus first formally gave the hart's-tongue fern the binomial Asplenium scolopendrium in his Species Plantarum of 1753. A global phylogeny of Asplenium published in 2020 divided the genus into eleven clades given informal names pending further taxonomic study; A. scolopendrium belongs to the "Phyllitis subclade" of the "Phyllitis clade".
1.2 Etymology
The supposed resemblance of the leaves to the tongue of a hart — an archaic term for a male red deer — gave rise to the common name "hart's-tongue fern". The Latin specific epithet scolopendrium is derived from the Greek skolopendra, meaning a centipede or millipede, this being due to the sori pattern on the underside of the frond being reminiscent of a myriapod's legs. The genus name Asplenium derives from the Greek words a- (meaning "without") and splēn (meaning "spleen"), reflecting an ancient belief that the plant's structure could remedy spleen disorders; this etymology stems from the doctrine of signatures, in which plant features resembling human organs indicated their therapeutic use.
1.3 Botanical Description
Asplenium scolopendrium, commonly called hart's tongue fern, is a rhizomatous, evergreen fern that typically produces an erect-arching clump of tongue-shaped, leathery, bright green fronds (12–18 inches long) which may have wavy margins. The most striking and unusual feature of the fern is its simple, strap-shaped undivided fronds. On mature fronds, the underside is handsomely marked with conspicuous brown stripes — the sori that contain the plant's spores. The rhizome is branching, short and ascending, lying partly above and partly below the surface of the soil.
1.4 Subspecies and Varieties
Morphological differences between varieties are minor, but the North American variety americanum is tetraploid, while the Old World subspecies (A. scolopendrium ssp. scolopendrium) is diploid. The American variety has a chromosome count of 144, while the European variety has a count of 72. The subspecies scolopendrium occurs throughout Europe (including the Caucasus and the British Isles), but is absent in northeast Europe (Finland, Belarus, Latvia, Lithuania, and European Russia); beyond Europe, it is found in the Middle East and North Africa, including Morocco, Algeria, Tunisia, Libya, and the Canary Islands.
1.5 Natural Habitat and Sourcing
Hart's tongue fern grows year-round in woodland, hedgerows, and sheltered places. A characteristic leathery, entire-leaved, strap-shaped wintergreen perennial fern of more or less permanently damp, base-rich habitats, the species is very widely distributed and common throughout most of Britain and Ireland. It is most frequent on limestone and scarce in upland areas where peat cover is extensive; typical habitats include woods, roadside banks, shady rocky slopes and damp walls, and it is particularly abundant in the cool, moist grykes (fissures) of limestone pavements.
1.6 Common Dosage Forms and Preparations
Hartstongue is a fern; the parts that grow above the ground are used to make medicine. The part used is the fronds. Traditional and contemporary preparations include:
- Infusion (herbal tea): An infusion is taken internally for the treatment of diarrhoea, dysentery, gravelly deposits of the bladder, and for removing obstructions of the liver and spleen.
- Decoction: A decoction of the fronds is used cosmetically as a hair wash to counteract greasy skin and also as a face pack for delicate skin.
- Ointment (topical): Externally it is used as an ointment in the treatment of piles, burns, and scalds.
- Tincture: In Bosnia and Herzegovina, Serbia, and Montenegro, a commercially available tincture of Asplenium scolopendrium can be found, marketed with indications including inflammation of gums, gingivitis, stomatitis, and periodontal diseases.
- Dried fronds: The fronds are harvested during the summer and can be dried for later use.
- Harvesting season: The plant is gathered in summer until spores are adequately mature.
2. Traditional and Historical Use
2.1 Classical Antiquity
The strap-like leaves were employed in ancient and medieval medicine. Dioscorides remarks on the bitterness of the leaves, but recommends that they be drunk with wine as an antidote to snakebite; he also prescribes a draught of 'phyllitis' for dysentery and diarrhea (De Materia Medica, III.121). The name 'Phyllitis' was the ancient name given to this fern by Dioscorides, which it has retained throughout the centuries. The Roman physician Galen is also reported to have employed the plant; the plant has been used for hundreds of years, with Galen himself recorded as using it.
2.2 Medieval European Medicine
The fern occupied a prominent place in the herbals of the medieval and early modern periods. The fifteenth-century Herbarius Latinus advocated a decoction of A. scolopendrium, drunk for forty days, to dissolve blockages of the spleen. The fern was also said to ease gout, clear eyes, heal fresh wounds, cool fever, and remove warts and pustules. The most frequent English common name, 'Hart's-tongue', first appeared in print as the Middle English 'hertes tongue' in the Grete Herball (Anonymous, 1526).
2.3 The Doctrine of Signatures
Much of the plant's medicinal reputation in European tradition was grounded in the doctrine of signatures. The sori on the fronds of Asplenium scolopendrium were considered to resemble the spleen, which caused the ancients to think the plant would be useful for treating ailments of the spleen. These applications were often based on the doctrine of signatures, linking the fern's tongue-like fronds to oral and throat ailments. Separately, in European folk medicine, ferns such as Asplenium scolopendrium were used to dissolve spleen blockages when consumed as a decoction over forty days, reflecting the genus's etymological association with spleen remedies derived from ancient Greek beliefs.
2.4 Nicholas Culpeper and Seventeenth-Century Herbalism
In Nicholas Culpeper's Complete Herbal (1653), the fern is commended against "the hardness and stoppings of the spleen and liver, the stone in the kidneys, all inward swellings especially in the veins and liver, pains in the joints, and the bloody flux"; the distilled water drunk twice a day is described as "singular" for those troubled with the stone in the reins or kidneys, while the juice dropped into the ears was said to take away pain and heal wounds, ulcers, and burns. Culpeper also noted its application in decoctions or ointments from fronds and rhizomes for treating earaches, skin conditions like burns and ulcers, and as a vulnerary for wound healing.
2.5 British and Irish Folk Medicine
The name 'Burntweed' originates from Westmeath, Wales, and the Scottish Highlands, and refers to the local use of the frond to manufacture an ointment for the treatment of burns, scalds, and piles (Britten & Holland, 1886; Grieve, 1931). Other medicinal uses in herbalism were as an astringent treatment for diarrhoea and dysentery, and as a remedy for removing obstructions from the liver and spleen (Grieve, 1931). Uses recorded from British and Irish folk medicine include colds and pulmonary congestion in Devon and the Hebrides, warts in Wiltshire, erysipelatoid eruptions on the legs on the Isle of Wight, and burns, insect stings, dog bites, jaundice, ringworm, and asthma in Ireland. In Scotland, fronds of hart's tongue were made into an ointment to treat piles, wounds, and scars, and on Skye, ale brewed from hart's tongue and maidenhair spleenwort was drunk for coughs and consumption.
2.6 Nineteenth-Century Folk Practice and Later Herbalism
This fern was used in the 1800s as a medicinal plant in folk medicine as a spleen tonic (hence an archaic name for the genus, "spleenworts"). The plant is harvested from the wild for local use as a medicine and hair conditioner. Traditional herbalists of the nineteenth and twentieth centuries classified the fronds' properties using Galenic humoral terms: the fronds are astringent, cholagogue, diaphoretic, diuretic, expectorant, and vulnerary.
2.7 Eastern European Ethnobotany
The ferns Asplenium ceterach L., Asplenium scolopendrium L., and Asplenium trichomanes L. have wide application in traditional medicine worldwide. Ethnobotanical records from Eastern Europe document the species in the folk medicine of the Caucasus region, the Balkans, Romania, and Azerbaijan. The plant has been documented in the ethnobotany of mountain regions of Eastern Europe. Traditional herbal teas incorporating A. scolopendrium have been recorded among minorities in the Balkans.
3. Key Constituents and Active Compounds
3.1 Overview of Phytochemical Profile
The plant extract contains phenolic compounds including tannins, phenolic acids, saponins, and flavonoids. A more detailed published inventory of active compounds identifies: main active compounds as tannins, choline, vitamin C, essential oils, mucilages, flavonoids (including kaempferol-7-rhamnoside-3-caffeoyl-7-diglucoside), thiaminase (probably present only in the fresh plant), saccharose, invert sugar, and terpenoids including lutein, (6S,9S)-roseoside, icariside B2, and picrionoside A.
3.2 Flavonoids
Asplenium scolopendrium has been revealed to display antioxidant activity related to the content of quercetin, rutin, kaempferol, kaempferol-3-O-glycoside, and luteolin. Key active compounds in A. scolopendrium include flavonoids such as kaempferol derivatives, which offer antioxidant and anti-inflammatory benefits. Powerful antioxidants such as genistein, quercetin, and caffeic acid have been identified from the leaves, though these compounds offer low efficacy and bioavailability as they are barely soluble in aqueous media.
3.3 Tannins
Tannins contribute astringent properties and support skin and wound applications. The qualitative phytochemical study of three Asplenium species from northern Iraq indicated positive tests for saponins, alkaloids, tannins, and flavonoids in the extracts.
3.4 Mucilage and Saponins
Mucilage provides demulcent and expectorant effects for respiratory soothing. Saponins are also present; the fronds, rhizome, and sori phytochemical investigation revealed the presence of several compounds including glycosides, lignins, quinones, tannins, and terpenoids in crude extracts of A. scolopendrium fronds.
3.5 Terpenoids
Terpenoid constituents of A. scolopendrium include the carotenoid lutein, the glycosidic roseoside, icariside B2, and picrionoside A. Icariside B2, which can be found in water extracts of A. scolopendrium, had a 19.4% inhibitory rate on hepatoma cancer cell invasion at a concentration of 10 µg/mL in earlier published research.
3.6 Thiaminase
Many ferns also contain thiaminase, an enzyme that robs the body of its vitamin B complex; in small quantities this enzyme will do no harm to people eating an adequate diet rich in vitamin B. The enzyme is destroyed by heat or complete drying, so cooking or adequately drying the plant will remove the thiaminase.
3.7 Fatty Acids
Oleic acid has been detected in significant amounts in samples of A. scolopendrium growing in Bulgaria. In a comparative chemical characterization of three ferns widely spread in Bulgaria — Asplenium ceterach L., Asplenium scolopendrium L., and Asplenium trichomanes L. — micro-elemental analysis was carried out using ICP-MS, and standard laboratory methods were used to determine the content of proteins, fats, and fatty acids.
4. Scientific Evidence by Area of Use
Overarching note on evidence quality: Despite the fact that Asplenium scolopendrium L. is a widespread fern which has been used as a human remedy for centuries, there are very poor or no data about the activity and genotoxicity of A. scolopendrium extracts. No formal randomized controlled clinical trials (RCTs), systematic reviews, or regulatory monographs (e.g., EMA, WHO, Commission E) specific to hartstongue as a supplement were located. All scientific evidence reviewed below is preclinical (in vitro or laboratory-based). No human clinical trials specific to hartstongue have been published in the peer-reviewed literature accessible via standard databases.
4.1 Antimicrobial Activity
Evidence level: Weak/Negative — in vitro only.
Despite the fact that Asplenium scolopendrium L. has been used as a human remedy for centuries, in one study vacuum-dried water and ethanol extracts of A. scolopendrium fronds were tested for their antimicrobial potential; antimicrobial activity was evaluated by disk diffusion assay at concentrations of 35 mg/mL, 7 mg/mL, and 1.4 mg/mL, and there was no inhibition zone for all extracts and for all microorganisms examined (Escherichia coli, Staphylococcus aureus, and Candida albicans).
Similarly, water and ethanol extracts of Asplenium scolopendrium L. fronds prepared by traditional methods for preparation of infusion and tincture did not show antimicrobial effects. A separate Iranian study screened the methanol extract of A. scolopendrium against Escherichia coli and Staphylococcus aureus, finding it less active than several other fern species tested in the same study. The extract from A. scolopendrium displayed the lowest activity among the three studied fern species — A. ceterach, A. trichomanes, and A. scolopendrium — in an in vitro Bulgarian investigation using agar diffusion assays. The existing in vitro evidence does not support antimicrobial activity for commonly prepared water or ethanol frond extracts of hartstongue.
4.2 Antioxidant Activity
Evidence level: Preliminary — in vitro only.
Comparison of results from phytochemical analyses shows a positive correlation between specific fatty acid composition, phenolic acids, and flavonoid content of Asplenium extracts and their biological activity. Asplenium scolopendrium has been revealed to display antioxidant activity related to the content of quercetin, rutin, kaempferol, kaempferol-3-O-glycoside, and luteolin. Genistein, quercetin, and caffeic acid have been identified in the leaves and characterized as powerful antioxidants. Research into forming nanosuspensions of these constituents found that the RESSAS (Rapid Expansion of Supercritical Solution into Aqueous Solutions) process results in diminished agglomeration of the particles and enhanced antioxidant activity index for the extract. However, the extract from A. scolopendrium displayed the lowest antioxidant activity among the three studied fern species in the comparative Bulgarian investigation. All antioxidant data are from in vitro models; no human trials exist.
4.3 Anticancer / Cytotoxic Activity
Evidence level: Very preliminary — in vitro only; results mixed and weaker than related species.
Extracts derived from the aerial parts of A. ceterach, A. scolopendrium, and A. trichomanes were examined using a panel of in vitro assays with different bacterial and mammalian cells; the cytotoxicity and anticancer activity of the samples were analyzed by MTT and Trypan blue assays with three human (A549, FL, HeLa) and three murine (3T3, TIB-71, LS48) cell lines. The obtained results demonstrate selective anticancer activity of all three Asplenium species. However, the extract from A. trichomanes demonstrated better anticancer and antibacterial properties than the sample from A. scolopendrium. A. trichomanes and A. scolopendrium extracts appeared to be potent inducers of necrotic cell death.
The extracts demonstrated a selective inhibitory effect against a cervical cancer cell line and low cytotoxicity against noncancerous human and mouse cells. Although extracts showed weak cytotoxic potential (NDI value decreased with increasing concentration of extracts), there was no statistical significance when compared to the negative control (p=0.055). These results are entirely in vitro and cannot be used to draw conclusions about effects in humans.
4.4 Cytogenotoxicity Studies
Evidence level: Preliminary — in vitro only; water extract did not show genotoxicity at tested concentrations.
Cytotoxic and genotoxic potential of extracts (70 mg/mL, 7 mg/mL, and 0.7 mg/mL) was tested using cytokinesis-block micronucleus cytome assay in human lymphocyte cultures; ethanol blocked division of cells in the negative control so only water extracts were analyzed. Water extract did not show genotoxic effects while cytotoxic effects were very weak.
Separately, a study examining ethanolic extracts of mature leaves and rhizomes for the phytosynthesis of silver nanoparticles found that the mito-stimulating effect of the extracts obtained from the leaves, and respectively the mito-inhibiting effect of the extracts from the rhizome, was augmented by the synthesis of Ag nanoparticles, which was associated with an increase in variability and frequency of chromosome aberrations. This nanoparticle-related finding is highly experimental and not relevant to conventional supplement preparations.
4.5 Digestive and Urinary System Effects
Evidence level: Traditional use only — no clinical studies identified.
People take hartstongue to treat digestive disorders and urinary tract diseases; hartstongue might help increase urine production, soften the stool, and stimulate the bowel to contract and empty. More evidence is needed to rate the effectiveness of hartstongue for these uses. These indications are based entirely on historical and folk use, not on clinical trial data.
4.6 Anti-Inflammatory Effects
Evidence level: Theoretical/in vitro — based on known properties of constituent flavonoids.
The anti-inflammatory potential of hartstongue is inferred from the general pharmacology of its flavonoid constituents — particularly quercetin, kaempferol, and genistein — which have been studied in vitro in multiple contexts. No studies examining anti-inflammatory outcomes specifically with A. scolopendrium whole extracts in human or animal models were located in the peer-reviewed literature. The phytochemical basis for the traditional anti-inflammatory attribution rests on the presence of these flavonoids, which have documented NF-κB and iNOS inhibitory activity in cell models.
5. Body Systems and Health Areas Associated with Hartstongue
- Hepatic and splenic system: Historical primary indication. Used in decoction for "obstructions" of the liver and spleen. Basis is entirely traditional; no clinical evidence.
- Digestive system: An infusion taken internally for the treatment of diarrhoea, dysentery, and gravelly deposits of the bladder. Dioscorides prescribed a draught of 'phyllitis' for dysentery and diarrhea.
- Urinary tract: People take hartstongue to treat urinary tract diseases. Diuretic properties are attributed in traditional herbal classification.
- Respiratory system: It is used as a member of herbal tea for treating wounds, diaphoretic, astringent, diuretic, as well as a therapy for cough and respiratory problems.
- Skin and wound healing: The local use of the frond to manufacture an ointment for the treatment of burns, scalds, and piles is well-attested across multiple British regional traditions.
- Oral cavity: A commercially available tincture of Asplenium scolopendrium is marketed for inflammation of gums, gingivitis, stomatitis, and periodontal diseases in several Balkan countries.
- Antioxidant protection (cellular): Attributed to the flavonoid fraction (quercetin, kaempferol, rutin, genistein, caffeic acid) identified in the fronds; characterization is in vitro only.
6. Dosage Forms and Dosages Reported in Sources
There are no established clinical doses derived from controlled human trials for hartstongue. The following represent dosage-related information as it appears in source materials:
- Frond infusion: Fronds collected in summer and dried for later use; specific gram-per-cup dosages are not stipulated in the primary herbals surveyed.
- Disk diffusion / in vitro antimicrobial testing concentrations: Antimicrobial activity was evaluated by disk diffusion assay at concentrations of 35 mg/mL, 7 mg/mL, and 1.4 mg/mL — no inhibition zone was found at any concentration.
- In vitro cytotoxic/genotoxic testing concentrations: Cytotoxic and genotoxic potential of extracts at 70 mg/mL, 7 mg/mL, and 0.7 mg/mL was tested using cytokinesis-block micronucleus cytome assay in human lymphocyte cultures.
- Medieval decoction regimen: The fifteenth-century Herbarius Latinus advocated a decoction of A. scolopendrium drunk for forty days to dissolve blockages of the spleen — a duration instruction, not a quantified dose.
- Commercial tincture (Balkan markets): Commercially sold in Bosnia, Serbia, and Montenegro; specific dosages on commercial products are not recorded in the research literature reviewed.
More evidence is needed to rate the effectiveness of hartstongue for its claimed uses, and no authoritative body (EMA, WHO, Commission E, ESCOP, NIH ODS) has issued a dosing monograph for this ingredient.
7. Safety Considerations
7.1 General Toxicity
Although no reports of toxicity have been found for this species, a number of ferns contain carcinogens so some caution is advisable. There isn't enough information available to know if hartstongue is safe or what the possible side effects might be.
7.2 Thiaminase Content
Many ferns also contain thiaminase, an enzyme that robs the body of its vitamin B complex. In small quantities this enzyme will do no harm to people eating an adequate diet that is rich in vitamin B, though large quantities can cause severe health problems. The enzyme is destroyed by heat or thorough drying, so cooking the plant will remove the thiaminase. This is particularly relevant to preparations made from fresh or inadequately dried fronds.
7.3 Rhizome vs. Frond: Differential Cellular Effects
In vitro studies found that leaves extract enhanced mitotic cell division, while rhizome extract had a mitodepressive effect. This differential cellular behavior between the frond and rhizome fractions, observed at experimental concentrations in plant cell models, underscores that preparations made from the rhizome may have different biological profiles than those made from the fronds — consistent with the traditional emphasis on fronds as the medicinal part used.
7.4 Genotoxicity
Water extract did not show genotoxic effects while cytotoxic effects were very weak in the cytokinesis-block micronucleus cytome assay in human lymphocytes. This is a single in vitro study and does not constitute comprehensive genotoxicity clearance.
7.5 Tannin-Related Interactions
The tannin content of hartstongue fronds is relevant to potential interactions with concurrent supplementation or dietary patterns. As a general property of plant tannins, high intake can inhibit non-heme iron absorption from the gut — a mechanism well-established for tannin-rich botanical preparations. Persons with iron-deficiency anaemia or those taking iron supplements should be aware of this potential for reduced iron bioavailability when consuming tannin-containing plant infusions at high frequency or volume.
7.6 Absence of Safety Data
No safety data from human clinical trials, pharmacovigilance databases, or regulatory toxicological assessments specific to A. scolopendrium supplements were identified. The RxList database entry for hartstongue states explicitly that there isn't enough information available to know if hartstongue is safe or what the possible side effects might be. No interactions with pharmaceutical drugs have been formally documented in the peer-reviewed literature reviewed.
References
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