How does it feel?
Unusually for a member of the Lamiaceae (mint) family, this plant has only very slight aromatic qualities, more noticeable when the leaves are crushed, yet quite distinctive and unique to bugleweed having been described as having an odour that is agreeable yet peculiar and somewhat reminiscent of turpentine. Its taste is similar and both the bitter and astringent properties of the plant are immediately detectable by the tongue and tissues of the mouth (1,2,3,4).
What can I use it for?
Bugleweed (Lycopus europaeus) Bugleweed can be taken as tea or tincture and is used to relieve some of the symptoms associated with an overactive thyroid gland, such as a rapid pulse, palpitations, nervousness, anxiety and insomnia. It may also be useful in situations where a raised heart rate or blood pressure is as a result of stress or anxiety as well as other stress-related cardiac conditions such as angina. However, it needs to be noted that both hyperthyroid and cardiovascular issues are serious, potentially life-threatening conditions with complex physiological causes and should be treated under the guidance of a qualified medical practitioner (5,6).
The bronchodilating and relaxing expectorant actions of bugleweed contribute to its benefit in treating conditions of the lungs such as chronic dry coughs, particularly if a rapid pulse and fever are accompanying symptoms. These properties, alongside its nervine effects may also be of benefit in cases of mild controlled asthma (3,6,7,8).
Due to both the seriousness of the conditions that bugleweed is indicated for, and the evidenced endocrine-modulating effects of the plant, some consider it should be used under practitioner guidance only (9).
Into the heart of bugleweed
Bugleweed (Lycopus europaeus) Both gypsywort (Lycopus europaeus) and bugleweed (Lycopus virginicus) are often used interchangeably within herbal medicine. The constituent profile and medicinal actions and indications of the two species are almost identical. The difference between the two species lies with their native lands — with bugleweed found in Europe, and bugleweed in North America. Where discussed herein, the qualities of the one species may be considered to be too possessed by the other. Energetically, bugleweed brings the virtues of calm equanimity, particularly to situations where there is anxiety and hyper-vigilance, cooling excessive heat from a situation and encouraging nourishment and rest when needed.
It is used homeopathically for patients with a specific symptom picture. These patients are described as being restless but tending towards paleness rather than cyanosis. The idea, or smell of food, often repulses them and their distress increases should they turn to lie on their right side. Their primary symptom however is always “a horrible tumultuous sensation in the cardiac region”(10,11).
In folklore, bugleweed was associated with having mystical powers to ward off evil spirits and protect against witchcraft and, perhaps paradoxically, is said to have been used in rituals and spells (12).
Traditional uses
Bugleweed (Lycopus europaeus) Bugleweed was included in the materia medica of the Eclectic medicine practitioners, a movement founded in early 19th century North America. This movement was considered revolutionary at the time for their ethos of using plant-based medicines as an alternative to some of the more extreme medical practices of the day, such as prescribing toxic chemicals and extensive bloodletting. The study of plants native to the Americas compiled by these practitioners validated and recognised the knowledge and experience of traditional herbalists.
Bugleweed was considered by the Eclectics of the time as primarily indicated for conditions of the heart and lungs specifically “vascular excitement, with rapid, tumultuous action of the heart but lacking power”; along with any condition that presented with a fast pulse. There are also some significant correlations between the symptom picture of “wakefulness and morbid vigilance with an inordinately active circulation and rapid pulse” for which traditionally, bugleweed was specifically indicated. Modern evidence-based research supports this use for the treatment of hyperthyroid conditions (13,14).
Ellingwood (1852–1920) described the specific symptomatology that would indicate the use of bugleweed to be:
“In diseases of the heart, either functional or organic, marked by irritability and irregularity of the organ, dyspnea, feeling of oppression in the cardiac region, its administration is followed by gratifying results.”
He describes its action as being similar to digitalis (or digoxin — a cardiac glycoside and pharmaceutical originally derived from foxglove, Digitalis purpurea) in reducing a rapid pulse rate but without the cumulative effects. Alongside his suggested uses for bugleweed in cardiac conditions such as pericarditis and endocarditis, it is also recommended for “inflammatory diseases of drunkards” and occasionally to cure cases where nothing else has worked (15).
An earlier American medicinal botanist and author, Constantine Samuel Rafinesque , who wrote and self-published his book, Manual of the Medical Botany of the United States of North America in Philadelphia in 1828, also notes in this work the somewhat similar effects of bugleweed on the pulse to digitalis but without the undesirable effects associated with its bioaccumulation (5).
Traditional actions
Herbal actions describe therapeutic changes that occur in the body in response to taking a herb. These actions are used to express how a herb physiologically influences cells, tissues, organs or systems. Clinical observations are traditionally what have defined these actions: an increase in urine output, diuretic; improved wound healing, vulnerary; or a reduction in fever, antipyretic. These descriptors too have become a means to group herbs by their effects on the body — herbs with a nervine action have become the nervines, herbs with a bitter action are the bitters. Recognising herbs as members of these groups provides a preliminary familiarity with their mechanisms from which to then develop an understanding of their affinities and nuance and discern their clinical significance.
Traditional energetic actions
Herbal energetics are the descriptions Herbalists have given to plants, mushrooms, lichens, foods, and some minerals based on the direct experience of how they taste, feel, and work in the body. All traditional health systems use these principles to explain how the environment we live in and absorb, impacts our health. Find out more about traditional energetic actions in our article “An introduction to herbal energetics“.
Western energetics
What practitioners say
Bugleweed (Lycopus europaeus) Endocrine
Whilst herbal medicine focuses on the principle of treating the whole person and the underlying causes of disease rather than simply treating the symptoms, bugleweed is considered an organo-specific (has a particular affinity for a specific organ of the body) for the thyroid. It is often included in a prescription for patients with overactive thyroid conditions such as Grave’s disease, based on both traditional use and more recent research and clinical trials (2,16,17,18).
Studies dating back to the 1950s support the current clinical usage of this herb having evidenced its efficacy for reducing the symptoms of hyperthyroidism including cardiac related symptoms including rapid heart rate, wiry thin pulse and palpitations with increased body temperature often associated with an overactive thyroid(2,14,19). Furthermore, it has been demonstrated to significantly reduce the extent of cardiac hypertrophy and reduce beta-adrenoceptor density in the heart with a similar efficacy to a commonly prescribed beta-blocker used for the treatment of high blood pressure, tachycardia (fast pulse) and arrhythmias (2,14). Its nervine, slightly sedative actions add to its virtues for addressing other frequently seen aspects of an over-active thyroid such as anxiety, nervousness, hyper-vigilance or insomnia (20).
For the treatment of hyperthyroid conditions bugleweed combines well with other cardiotonic and nervine herbs such as hawthorn (Crataegus spp.), motherwort (Leonurus cardiaca) and lemonbalm (Melissa officinalis) (5,8,16,18,21).
Cardiovascular
In addition to its benefit in reducing thyroid-associated cardiac symptoms, bugleweed has been seen to be an effective remedy for cardiovascular conditions of a nervous origin, such as nervous tachycardia, palpitations, angina and other stress-related causes of chest pain (1,6,16). It may be included in a formula for a patient with a rapid, wild pulse that is wiry and thin; or irregular and tumultuous (19).
Similarly to hawthorn, bugleweed is regarded as having cardiotonic properties and the combined action of its positively inotropic (increases force of contraction) and negatively chronotropic (decreases rate of contraction) effects result in a strengthening of the force of the heart muscle allowing it to expel a greater volume of blood with each contraction, the outcome of this increased efficiency subsequently results in a reduced heart rate. This strengthening action on the heart justifies its inclusion in the treatment of cardiac conditions such as cardiac or venous insufficiency, congestive heart failure or heart related oedema (6,16).
Nervous
Bugleweed has been noted for its sedative and nervine actions and may be used for a range of conditions that are exacerbated by anxiety, stress or are of a nervous origin (3,6,16). Its potent anxiolytic action induces relaxation and is of benefit in states where there is irritability, hypervigilance or sensitivity, particularly in cases where this leads to insomnia (22).
Respiratory
Bugleweed may be described as a nervine for the lungs. Its relaxing expectorant and bronchodilating actions provide relief in respiratory conditions such as dry irritating coughs, chronic bronchitis, bronchial spasm, chronic asthma, combining well with other herbs that support the lungs such as elecampane (3,5,6,16,22). It may also be included in formulas when otherwise mild colds with no other significant complications are nonetheless accompanied by an ongoing irritating or debilitating cough (20).
Another lesser-known use of bugleweed in modern herbal practice is as a calming bitter, which can be helpful in some cases of indigestion or chest pain related to acid reflux (5,6).
Although not in itself considered to have immune-modulating properties, its diaphoretic effects support optimal functioning of the innate immune system and it has traditionally been used as a herb to manage fever (6,23). In more recent studies, it has been demonstrated to have a positive herb–drug interaction with some antibiotics increasing their efficacy against drug resistant strains of bacteria potentially increasing its realm of value in herbal medicine and promoting integrative practice between healthcare providers (14,24).
Research
Bugleweed (Lycopus europaeus) A review on Lycopus europaeus: A potential medicinal plant
A review published in 2019 examined the phytochemical constituents of gypsywort in the context of their potential therapeutic and pharmacological properties. It concluded that bugleweed exhibited actions that correlate with its use in both traditional and modern herbal practices including endocrine modulation; particularly with regard to the thyroid, antimicrobial, antitussive and hypnotic effects that are frequently seen to be of equal efficacy to commonly used prescription-only-medications.
The study suggests that rosmarinic acid, a predominant constituent found in gypsywort as well other herbs used for treating hyperthyroid conditions such as self-heal (Prunella vulgaris) and lemon balm, has a number of significant actions on thyroid function. This includes inhibiting conversion of T4 to T3 and decreasing the stimulation of the thyroid by thyroid stimulating hormone (TSH). Studies of human patients with conditions involving over-activity of the thyroid further reported that treatment with low dosages of gypsywort resulted in an improvement in cardiac-related symptoms on almost equal efficacy to that of a commonly prescribed beta-blocker medication, despite test results indicating no significant changes in levels of thyroid hormones or TSH.
Euroabienol, a constituent belonging to the diterpenoid chemical group, was screened for its potential antimicrobial action against a wide range of bacteria and fungi, including Staphylococcus aureus strains originating from skin and catheter-related infections. It demonstrated significant activity against all samples tested including methicillin and poly-resistant strains.
An alcohol extraction of bugleweed given at low dosages was seen to be considerably more effective as an antitussive than the standard drug diphenhydramine hydrochloride. In studies using other common cough suppressant medications as a control, it was seen to significantly inhibit cough by up to 75%. The hypnotic properties of bugleweed were likewise compared to the effects of established sedating prescription-only drugs and was found to result in a reduction in sleep onset time similar to that induced by thiopental and diazepam (25).
Lycopus europaeus (gypsywort): Effects on the thyroidal parameters and symptoms associated with thyroid function
This observational study aimed specifically to examine potential reasons for the significant improvement in cardiac-related symptoms of hyperthyroid conditions with low dosages of gypsywort despite previous clinical studies having shown there to be no major changes to the thyroid hormone levels of these patients in contrast to the more obvious endocrine modulating effects on levels of T3, T4 and TSH seen at higher doses (26).
Extract of Lycopus europaeus L. reduces cardiac signs of hyperthyroidism
As previously, this research study examines the positive effects of low doses of gypsywort extracts with regard to cardiac related symptoms of hyperthyroidism in the absence of clinically reportable changes in pituitary or thyroid hormone levels in contrast to the endocrine modulating properties seen at higher doses. Low doses were confirmed to effectively reduce heart rate and blood pressure and raise body temperature, although weight and appetite appeared unaffected (27).
Bacterial resistance modifying agents from Lycopus europaeus
This study was conducted to inform an ongoing project identifying plants that show activity against multidrug resistant bacteria. A range of already known diterpene compounds found in bugleweed, along with two isopimarane diterpenes identified by the study, were tested against a number of strains of Staphylococcus aureus for evidence of antibacterial and resistance-modifying activity. Although the bugleweed extract at the dose given showed no significant antimicrobial activity, when used concurrently with the tetracycline and erythromycin it was seen to potentiate the activity of these antibiotics two-fold against S. aureus strains otherwise seen to be highly resistant to these antibiotics (24).
Did you know?
The name of this genus of plants, Lycopus, has its roots in the two Greek words lykos and pous, meaning wolf and foot. This etymology refers to the alleged resemblance of the upper leaves to the foot of a wolf, which is reflected in some of its other common folk names such as pied de loup (French) and wolfsfuss (German) (4,23).
All parts of bugleweed are edible along with the tubers and roots, described as having a flavour reminiscent of artichoke, being traditionally eaten raw, baked, boiled, roasted or dried for storage as an important staple food in some parts of North America. The young shoots can also be eaten as an early spring vegetable. The leaves, although quite bitter, can be added to salads or used in cooked food (28).
Additional information
Botanical description
Bugleweed is a perennial plant with the characteristic square stem of the mint (Lamiaceae) family to which it belongs although unlike many of the plants included in this family, it lacks any significant aromatic qualities only giving off a very mild unique odour when crushed.
Leaves are seen as opposite pairs varying in appearance from lance shaped with a toothed margin in the upper leaves in contrast to the wedge-shape and smooth margins of the lower leaves. The small flowers, which only bear two stamens distinguishing them from most other members of the mint family that have four, appear between July and September as whorls within the axils of the upper leaves. This plant spreads underground through its creeping rhizome (5,4,35,36).
Although the two species, L. europaeus and L. virginicus are considered by many to be medically interchangeable and share many common traits in appearance, there are also some subtle botanical differences that allow them to be visually distinguished from each other. The smooth stems of L. virginicus may reach between 15–60 cm in contrast to the longer and slightly hairy stems of L. europaeus which typically grow to 30–100 cm. L. europaeus is also seen to have narrower leaves on a more acutely angled stem with flowers that range in colour from white to pale flesh in contrast to the more purplish flowers of L. europaeus (4,35).
Common names
- Gypsywort
- Water bugle
- Water horehound
- Gypsyweed
- Paul’s betony
- Carpenter’s herb
- Wolf foot
Safety
Bugleweed is not considered safe for use during pregnancy or whilst breastfeeding. Along with herbs such as sage (Salvia officinalis), it may decrease milk supply in breastfeeding people. Due to the lack of clinical data, it is also advised that bugleweed is not given to children due to its antithyroid and antigonadotropic actions (1,2,17,29).
Rare cases have been reported involving the therapeutic use of bugleweed at high doses over extended periods of time that have resulted in enlargement of the thyroid. Other occasionally reported side effects from the clinical use of bugleweed include headache, increase in thyroid size and, less frequentlyt, an increase in symptoms associated with hyperthyroidism, such as palpitations, fast heart beat, nervousness and weight loss (1).
Bugleweed should not be abruptly discontinued and instead gradually tapering down dosage is recommended, if treatment is to be stopped for any reason (2,17).
Interactions
Bugleweed should not be taken concurrently with any thyroid-modulating drugs, as it may reduce the intended therapeutic effects of these. It may also interfere with thyroid diagnostic procedures that use radioactive isotopes (1,17,30,31).
Contraindications
Contraindicated in underactive thyroid (hypothyroid conditions such as Hashimoto’s disease), cases of thyroid enlargement with no functional disorder, pregnancy and lactation.
Women who are trying to conceive are cautioned against taking preparations containing bugleweed as there is evidence to suggest it may possess contraceptive effects with longer-term usage (3,17,32).
It is recommended by some herbal practitioners that bugleweed should only be taken under professional guidance (9).
Preparations
- Tincture
- Fluid extract
- Infusion
- Glycerite
Dosage
- Tincture (ratio 1:5 | 45%): 3–6 ml per day
- Fluid extract (1:1 | 45%): 1–3 ml per day
- Liquid extract (1:2 | 45%): 2–6 ml per day
Infusion: 1–2 g of dried herb per day - Dried extract: Equivalent of 20 mg of herb per day as capsule or pill form
It is generally recommended that the above daily dosage are divided into three equal doses and taken thrice daily at regular intervals, unless otherwise directed by a herbal practitioner. Tinctures may be taken neat or in a little water, if preferred (1,2,3,16,33).
Plant parts used
Aerial parts whilst in flower
Constituents
- Phenolic compounds: Flavonoids with a predominance of 7-O-β-D-glucuronides of apigenin, acacetin, and luteolin, tannins, Rosmarinic acid and other phenolic acid derivatives including caffeic, chlorogenic and ellagic acids (2,17,32)
- Terpenoid compounds: Eurobienol (2,17,32)
- Volatile oils (2,17,32)
- Alkaloids (2,17,32)
Habitat
Although native to different regions of the world both species are found within similar habitats preferring damp shady ground such as river or canal banks, marshes, woodlands, ditches and fens. L. europaeus is native to Europe being found commonly throughout England and Wales, although rarer in Scotland and Ireland, whereas L. virginicus is a native plant of North America (2,34,35,36).
Sustainability
This species is classed as Least Concern as it is widespread and abundant throughout its European and East Mediterranean range with stable populations and does not face any major threats (33,37,38).Habitat loss and over-harvesting from the wild are two of the biggest threats faced by medicinal plant species. There are an increasing number of well-known herbal medicines at risk of extinction. We must, therefore, ensure that we source our medicines with sustainability in mind.
The herb supplement industry is growing at a rapid rate and until recent years a vast majority of medicinal plant produce in global trade was of unknown origin. There are some very real and urgent issues surrounding sustainability in the herb industry. These include environmental factors that affect the medicinal viability of herbs, the safety of the habitats that they are taken from, as well as the welfare of workers in the trade.
The botanical supply chain efforts for improved visibility (transparency and traceability) into verifiably sustainable production sites around the world is now certificated through the emergence of credible international voluntary sustainability standards (VSS).
Read our article on Herbal quality and safety: What to know before you buy and Sustainable sourcing of herbs to learn more about what to look for and questions to ask suppliers about sustainability.
Quality control
Herbal medicines are often very safe to take; however, their safety and efficacy can be jeopardised by quality issues. So, it is important to buy herbal medicines from a reputable supplier, from sources known to test their herbs to ensure there is no contamination, adulteration or substitution with incorrect plant matter, as well as ensuring that recognised marker compounds are at appropriate levels in the herbs.
Some important quality assurances to look for are certified organic labelling, the correct scientific/botanical name, and the availability of information from the supplier about ingredient origins. A supplier should be able to tell you where the herbs have come from, what contaminants are not in the herb, and what the primary compounds are.
How to grow
Bugleweed grows well in a range of soil types from light sand to heavy clay and is tolerant of a soil pH of between mildly acidic to mildly alkaline. Thriving in moist or wet soil, it prefers semi or no shade. It can be easily grown from seeds or root cuttings and once established spreads prolifically through both the root structure and self-seeding (35,39,40).
Recipe
Bugleweed glycerite
Glycerites are an excellent way to preserve plant juices and can be used as an alternative to alcohol to extract the medicinal properties of herbs. For more information about making glycerites see our page on medicine making.
Ingredients
- Fresh bugleweed herb
- Glycerine
Method
- Harvest the aerial (above-ground) parts of bugleweed during early flowering
- Chop finely and put into a clean and sterile jar until full
- Pour glycerine over the herbs up to 2.5 cm below top of the jar
- To ensure herbs are covered and any air bubbles are released press down gently on the herb material with a wooden implement.
- Leave in a cool dark place for a month, gently shaking the bottle every couple of days.
- Strain through muslin or fine cotton to remove the plant material
- Bottle and label with the name of the preparation and the date made. Glycerites have a shelf life of around a year.
References
- Bone K. A clinical guide to blending liquid herbs: Herbal Formulations for the Individual Patient. Elsevier Health Sciences; 2003.
- Thomsen M. The Phytotherapy Desk reference: 6th Edition. Aeon Books; 2022.
- Bartram T. Encyclopedia of Herbal Medicine. Grace publishers; 1995.
- Lycopus.—Bugleweed. | Henriette’s herbal homepage. https://www.henriettes-herb.com/eclectic/kings/lycopus.html
- Bruton-Seal J, Seal M. Wayside Medicine: Forgotten plants to make your own herbal remedies.; 2017.
- Coffman S. Herbal medic: A Green Beret’s Guide to Emergency Medical Preparedness and Natural First Aid. Hachette UK; 2021.
- Wren RC, Williamson EM, Evans FJ. Potter’s new Cyclopaedia of Botanical Drugs and Preparations. C.W. Daniel Company, Limited; 1988.
- Easley T, Horne S. The modern herbal Dispensatory: A Medicine-Making Guide. North Atlantic Books; 2016.
- Chevallier A. Encyclopedia of Medicinal Plants.; 2001.
- Walker WT. The clinical management of hypertension. British Homeopathic Journal. 1984;73(02):98-106. doi:10.1016/s0007-0785(84)80026-5
- Borland DM. Acute cardiac emergencies. Hahnemannian. 1964 Mar;99:8-10. PMID: 14128894.
- Gypsywort plant – Learn about growing and caring for this wildflower | WildflowerWeb. http://www.wildflowerweb.co.uk/plant/229/gypsywort#:~:text=In%20addition%20to%20its%20medicinal,in%20various%20rituals%20and%20spells.
- Exploring the Eclectics and the Eclectic medical Movement. Eclecticherb. Published September 9, 2024. https://eclecticherb.com/blogs/news/exploring-the-eclectics-and-the-eclectic-medical-movement?srsltid=AfmBOop-OpFfGSGZphYrhKaNDVyXTUSvOfcnoebaNU_qm3qU-DJTXuvY
- Yarnell E, Abascal K. Botanical Medicine for Thyroid Regulation. Alternative and Complementary Therapies. 2006; 12(3):107-112. doi: 10.1089/act.2006.12.107
- Ellingwood F Jr. GROUP II. Agents Acting Upon the Heart :1-3. https://swsbm.com/Ellingwoods/Group_2.pdf
- Hoffmann D. Medical Herbalism: The Science and Practice of Herbal Medicine. Simon and Schuster; 2003.
- Mills SY, Bone K. The essential guide to herbal safety. Elsevier Health Sciences; 2004.
- Barker J. Human Health and its Maintenance with the Aid of Medicinal Plants. Aeon Books; 2020.
- Wood M. The Earthwise Herbal Repertory: The Definitive Practitioner’s Guide. North Atlantic Books; 2016.
- Stansbury J. Herbal Formularies for Health Professionals, Volume 2: Circulation and Respiration, including the Cardiovascular, Peripheral Vascular, Pulmonary, and Respiratory Systems. Chelsea Green Publishing; 2018.
- Stansbury J. Herbal Formularies for Health Professionals, Volume 3: Endocrinology, including the Adrenal and Thyroid systems, Metabolic endocrinology and the reproductive Systems. Chelsea Green Publishing; 2018.
- Bugleweed Monograph — HerbRally. HerbRally. https://www.herbrally.com/monographs/bugleweed
- Leyel C.F. Compassionate herbs. Faber & Faber; 1946
- Gibbons S, Oluwatuyi M, Veitch NC, Gray AI. Bacterial resistance modifying agents from Lycopus europaeus. Phytochemistry. 2002;62(1):83-87. doi:10.1016/s0031-9422(02)00446-6
- Al-Snai, A. E. . A review on Lycopus europaeus: A potential medicinal plant. IOSR Journal of Pharmacy, 9(7), 80-88.
- Beer A m., Wiebelitz KR, Schmidt-Gayk H. Lycopus europaeus (Gypsywort): Effects on the thyroidal parameters and symptoms associated with thyroid function. Phytomedicine. 2007;15(1-2):16-22. doi:10.1016/j.phymed.2007.11.001
- Vonhoff C, Baumgartner A, Hegger M, Korte B, Biller A, Winterhoff H. Extract of Lycopus europaeus L. reduces cardiac signs of hyperthyroidism in rats. Life Sciences. 2005;78(10):1063-1070. doi:10.1016/j.lfs.2005.06.014
- Sweet H. Bugleweed, wild edible and alternative herbal remedy. Eat the Planet. Published May 4, 2020. https://eattheplanet.org/bugleweed-wild-edible-and-alternative-herbal-remedy/
- Bone K, Mills S. Principles and practice of phytotherapy: Modern Herbal Medicine. Elsevier Health Sciences; 2013.
- Brinker F. Herb contraindications & drug interactions. Eclectic medical press; 1998.
- NatMed Pro. https://naturalmedicines.therapeuticresearch.com/
- Al-Snafi NAE. Medicinal plants with endocrine modulating effects. GSC Biological and Pharmaceutical Sciences. 2023;24(1):174-192. doi:10.30574/gscbps.2023.24.1.0276
- ABC Herbalgram website. https://www.herbalgram.org/resources/commission-e-monographs/monograph-approved-herbs/bugleweed/
- Phillips R, Grant S. Wild flowers of Britain. Mad River PressInc; 1977.
- Phillips R., Foy N. Herbs. Pan books Ltd; 1990
- Rose F, O’Reilly C. The wild flower key: How to Identify Wild Flowers, Trees and Shrubs in Britain and Ireland. Frederick Warne Publishers; 2006.
- Lycopus L. | Plants of the World Online | Kew Science. Plants of the World Online. https://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:30028551-2
- https://www.iucnredlist.org/species/163972/42319751
- Lycopus virginicus Bugleweed, Virginia water horehound PFAF Plant Database. https://pfaf.org/user/Plant.aspx?LatinName=Lycopus+virginicus
- Lycopus europaeus Gypsywort PFAF Plant Database. https://pfaf.org/user/Plant.aspx?LatinName=Lycopus+europaeus
