Sundew (Drosera rotundifolia): Properties and Benefits

Drosera rotundifolia L. / Sundew, known in English as round-leaved sundew or common sundew, is a perennial carnivorous herb of the Droseraceae family, described by Carl Linnaeus in 1753. With a circumboreal distribution, the species grows in bogs, mires and marshes across Europe, Siberia and North America, always on waterlogged, acidic and nutrient-poor soils. The sundew is easy to recognize by its basal rosette of rounded leaves, covered with glandular tentacles that secrete a sticky mucilage used to trap insects, while its delicate white or pinkish flowers open at the top of thin, upright stalks that bring a touch of beauty to these wet, acidic habitats.

The use of Drosera rotundifolia in traditional European medicine goes back a long way, and tradition credits the Italian physician Matthaeus Platearius, of the School of Salerno, with one of the earliest records of the plant as a remedy, as early as the 12th century. Since then, European herbalists have recommended it for a range of respiratory complaints, such as persistent cough, bronchitis and asthma. Its composition, rich in naphthoquinones and flavonoids, underlies the expectorant, antispasmodic and anti-inflammatory actions that tradition attributes to it, and recent laboratory studies are investigating these compounds, although robust clinical trials confirming the traditional uses in people are still lacking.

Popular and International Names of Sundew

• English: common sundew, dew plant, red rot, round-leaved sundew, roundleaf sundew, sundew.
• French: droséra à feuilles rondes, rossolis à feuilles rondes.
• German: Rundblättriger Sonnentau, Sonnenthau.
• Italian: rosolida, rugiada, rugiada del sole.
• Portuguese: drósera (Brazil), orvalhinha (Portugal), orvalho-do-sol, papa-moscas, rorela.
• Spanish: atrapamoscas, hierba de la gota, hierba del rocío, rocío de sol, rocío de sol de hojas redondeadas.

Botanical Synonyms of Drosera rotundifolia

The scientific name Drosera rotundifolia L. is widely accepted and recognized by the main botanical nomenclature databases, and the stability of the binomial coined by Linnaeus in 1753 reflects both the precision of the original description and the broad acceptance it gained in the scientific community. Over the history of botany, however, other names have been proposed for the species, and some of these synonyms, though uncommon in current literature, still turn up in older records or in specific taxonomic contexts.

• Rorella rotundifolia (L.) All.

The combination in the genus Rorella was proposed by the Italian botanist Carlo Allioni in the 18th century, and the name, derived from the Latin ros, dew, echoes in the Portuguese common name rorela.

Botanical Family: Droseraceae

The Droseraceae family brings together carnivorous plants of the genera Aldrovanda, Dionaea (the well-known Venus flytrap) and Drosera, all shaped by adaptation to nutrient-poor soils, to which they responded with sophisticated mechanisms for capturing and digesting insects. Species in the family are found in many regions of the world and favor wet habitats such as marshes, peat bogs and heaths, where the roots find little available nitrogen and catching prey makes up for that shortfall.

As a member of this family, Drosera rotundifolia is a fine example of the evolutionary ingenuity of carnivorous plants, since its glandular tentacles, which secrete a sticky substance, allow it to catch small prey and absorb essential nutrients from them. Because of this unusual biology, the Droseraceae family interests botanists and ecologists not merely as a curiosity but also as a model for understanding how plants adapt to challenging environmental conditions.

Parts of Sundew Used

• Flowers and flower stalks
• Leaves of the basal rosette, with their glandular tentacles
• Whole plant, mainly the aerial parts

In herbal medicine, sundew is usually employed whole, with a focus on the aerial parts, that is, the leaves and flowers, which hold most of the bioactive compounds described for the species. The material is used dried to prepare teas, tinctures, extracts and syrups, and responsible harvesting is crucial, since the plant is small and its wild populations are protected in several European countries.

Ethnobotanical and Traditional Uses

Drosera rotundifolia has a long history of ethnobotanical use and was valued by different European cultures over the centuries, above all as a remedy for respiratory problems. Tradition credits Matthaeus Platearius, of the renowned School of Salerno, with one of the earliest records of its medicinal properties, particularly its use against coughs, and this custom endured through the centuries until sundew became a frequent ingredient in herbal preparations for the respiratory tract.

Traditionally, sundew has been used to relieve persistent coughs, bronchitis, asthma and whooping cough, and its antispasmodic and expectorant action was especially prized for soothing throat irritation and helping to clear mucus. In homeopathy, Drosera rotundifolia is also indicated for hoarseness and other respiratory conditions, and this old knowledge continues to guide modern herbal medicine, which seeks to investigate with scientific methods what tradition recorded. Traditional and homeopathic records mention the plant mainly in the following contexts:

• Asthma, as traditional support and never as a replacement for medical treatment
• Bronchitis and catarrh of the airways
• Hoarseness
• Persistent cough, whether dry or spasmodic
• Throat irritation and laryngitis
• Whooping cough, a historical use that predates vaccines and antibiotics

Therapeutic Properties of Sundew

The properties below summarize what tradition and laboratory studies attribute to sundew, and none of them has been confirmed by large clinical trials in humans.

• Antibacterial (activity observed in laboratory studies, including against bacterial biofilms)
• Anti-inflammatory (preliminary laboratory studies)
• Antitussive (best-known traditional use, to calm coughing)
• Bronchial antispasmodic (traditional record of relief from bronchial spasms)
• Bronchodilator (effect on airway muscles investigated in experimental studies)
• Calming (traditional record)
• Diuretic (traditional record of increased urine output)
• Emollient (traditional record of protection of the mucous membranes, linked to its mucilages)
• Expectorant (traditional record of helping to clear mucus)
• Mucolytic (traditional record of thinning mucus)

Detailed Phytochemical Profile of Sundew

Pharmacological interest in Drosera rotundifolia lies in its phytochemical makeup, which brings together several classes of bioactive compounds. Naphthoquinones are among the most studied groups, notably plumbagin, droserone, 7-methyljuglone, ramentaceone, ramentone and biramentaceone, substances that laboratory studies associate with antimicrobial and anti-inflammatory activity and that help explain the plant’s traditional use for respiratory complaints. Plumbagin, however, can also irritate the mucous membranes when ingested in excess, which is why prolonged internal use or high doses are not recommended.

Besides naphthoquinones, sundew contains flavonoids such as quercetin, myricetin, hyperoside, isoquercitrin, kaempferol-3-O-β-galactopyranoside, astragalin and 2”-O-galloylhyperoside, with antioxidant and anti-inflammatory activity described in experimental studies that would complement the action of the naphthoquinones. A 2022 study examined extracts and flavonoids from the plant for their effects on ciliary beat frequency and on airway smooth muscle in mice, while another, from 2021, compared the metabolic profiles and biological activities of field-grown and in vitro propagated plants. The plant also contains phenolic acids, tannins, mucilages, to which its emollient action is attributed, organic acids and proteolytic enzymes, which it uses to digest its prey, in a combination whose interactions are still poorly understood.

• Flavonoids: 2”-O-galloylhyperoside, astragalin, hyperoside, isoquercitrin, kaempferol-3-O-β-galactopyranoside, myricetin and quercetin
• Mucilages
• Naphthoquinones: 7-methyljuglone, biramentaceone, droserone, plumbagin, ramentaceone and ramentone
• Organic acids: citric, malic and tartaric
• Phenolic acids
• Proteolytic enzymes
• Tannins

Preparation and Administration Forms of Sundew

Drosera rotundifolia can be prepared and taken in several ways, depending on the purpose and the guidance received. The infusion, known as tea, is one of the most popular and accessible ways to consume the plant, while tinctures and extracts offer a higher concentration of active constituents and tend to appear in more specific formulations, and homeopathy, for its part, uses sundew in diluted preparations according to its own principles.

• Alcoholic tincture
• Dried or fluid extract, usually in standardized products
• Homeopathic preparations in pillules or drops
• Infusion (tea) of the dried plant
• Syrup, often combined with other herbs

The choice of preparation should take into account the dose and the bioavailability of the compounds, and syrups and tinctures are usually preferred for acute coughs, while infusions are the simplest form, provided they are used for short periods. Whatever the form, it is advisable to follow the guidance of a health professional or the instructions on standardized products, especially because prolonged internal use or high doses are discouraged on account of the plant’s naphthoquinone content.

Synergy with Other Medicinal Plants

Traditional Combinations for Coughs and the Airways

In European herbal medicine, Drosera rotundifolia is traditionally combined with other medicinal plants in formulas for respiratory complaints. Tradition records its pairing with thyme (Thymus vulgaris) for bringing together expectorant and antiseptic actions, and licorice root (Glycyrrhiza glabra) enters these formulas for the emollient and anti-inflammatory properties attributed to it, used to soothe irritated airways. Mullein (Verbascum thapsus) and Grindelia robusta complete the group of traditional partners, the former associated with mucolytic effects and the latter with antispasmodic effects, and these combinations often appear in cough syrups and teas. Each plant has its own precautions, such as licorice, which is not suitable for people with high blood pressure, and any blend should be guided by a health professional.

Recipes and Usage Protocols of Sundew

Ros Solis Cordial (Historical Recipe)

Ros Solis cordial is a historical recipe in which Drosera rotundifolia leaves were steeped in spirits, to which spices such as cinnamon, cloves, ginger and nutmeg were added. Besides the medicinal use attributed to it, the liqueur was enjoyed for its flavor and aroma, and today it is of interest mainly as a document of pharmacy history, since it contains alcohol and has no defined dose, which makes it unsuitable for pregnant or breastfeeding women, children and anyone who needs to avoid alcoholic drinks.

Traditional Infusion for Coughs

In European tradition, an infusion of the dried herb of Drosera rotundifolia is traditionally used for coughs and irritation of the airways. To prepare it, place a small amount of the dried plant in a cup of boiling water, leave it to infuse for 5 to 10 minutes, then strain and drink.

The amount of plant, the number of cups per day and the duration of use should be set with professional guidance, because the naphthoquinone content discourages prolonged use or high doses; consult a health professional. The German Commission E, which assessed the herb in its own monograph, set a daily limit for the dried plant, which underlines that the dose should not be improvised.

Tincture

Drosera rotundifolia tincture is traditionally used for coughs as a concentrated and practical way of taking the plant’s active constituents, and it is usually diluted in water or juice before use. Because it is more concentrated than tea, it calls for extra care with dosing, which should be set by a health professional according to the product’s strength, the person’s age and the length of use, and, like any tincture, it contains alcohol, which makes it unsuitable for children, pregnant women and anyone who needs to avoid alcoholic drinks.

Syrups

Drosera rotundifolia is a common ingredient in syrups traditionally used for coughs, often alongside other herbs, in formulas intended to soothe the throat and ease expectoration. When using a commercial syrup, follow the manufacturer’s dosing and age instructions, check that the product is registered with the health authority and do not combine several cough syrups at the same time without professional advice.

The preparations above follow traditional records and do not replace professional guidance. Before any internal use, check the contraindications and interactions described in this article.

Associated Therapies

Western Herbal Medicine

In Western herbal medicine, Drosera rotundifolia is a recognized traditional remedy for various respiratory conditions and appears in infusions, tinctures and standardized extracts traditionally indicated for coughs, bronchitis and asthma. Its use rests mainly on tradition and on the German Commission E monograph, while modern laboratory studies investigate its active compounds, and the plant is valued for its reputed ability to calm bronchial spasms and support expectoration, though this never replaces medical assessment in cases of asthma or prolonged cough.

Homeopathy

Drosera rotundifolia is one of the best-known remedies in homeopathy, which indicates it mainly for spasmodic cough, bronchitis, laryngitis and hoarseness and, historically, also for whooping cough, a disease that requires medical diagnosis and treatment. Preparations come as pillules and in different potencies, such as 3X (3DH), 6CH, 9CH and 30CH, and, according to homeopathic principles, they would act by stimulating the body’s capacity for self-healing, a premise specific to this practice. Dosing should follow the advice of a qualified homeopath or the label instructions, and an in vitro study published in 2021 observed changes in gene expression in human bronchial epithelial cells exposed to low doses of the plant, a laboratory finding that does not demonstrate any clinical effect.

Contraindications and Side Effects of Sundew

Sundew, or round-leaved sundew (Drosera rotundifolia), is traditionally used as an antitussive and antispasmodic for the airways and is generally well tolerated at usual doses and for short periods, but, like any medicinal plant, it has contraindications and side effects that need to be known before use. The main precautions are: avoid prolonged internal use or high doses, because of the naphthoquinone content (plumbagin), which can irritate the mucous membranes in excess; do not use during pregnancy and breastfeeding without professional guidance; use caution in young children, preferring professional guidance for dosing; discontinue in case of gastric irritation.

Prolonged Use and High Doses

Naphthoquinones, especially plumbagin, account for part of the pharmacological interest in the plant, but in excess they can irritate the mucous membranes, so internal use should be limited to short periods and moderate doses set with a health professional. A cough that lasts more than a few weeks or comes with high fever, shortness of breath or blood needs medical assessment and should not be managed with home remedies alone.

Gastrointestinal Irritation

In some people, taking Drosera rotundifolia can cause mild gastrointestinal irritation, with stomach discomfort or nausea, particularly in more sensitive individuals. If these symptoms appear, stop using the plant and seek medical advice if the discomfort does not go away soon.

Pregnancy and Breastfeeding

During pregnancy and breastfeeding, sundew should not be used without professional guidance, because the lack of conclusive studies on the plant’s safety in these periods makes it prudent to avoid it unless a doctor specifically recommends it. This caution applies doubly to tinctures and liqueurs, which contain alcohol.

Young Children

In young children, greater caution is needed, and dosing should always be based on professional guidance, with age-appropriate products preferred over homemade preparations or alcoholic tinctures. Asthma and whooping cough, two conditions mentioned among the plant’s traditional uses, require medical diagnosis and follow-up, and no sundew preparation replaces vaccines, antibiotics or prescribed medicines.

Urine Discoloration

A minor effect, though one that may come as a surprise, is a change in urine color, described in herbal medicine sources as a consequence of internal use of the plant and linked to the presence of some of its compounds. The change is usually considered harmless, but if it comes with pain, fever or other symptoms, it is wise to seek medical assessment.

Drug Interactions

There is no detailed information on specific drug interactions of Drosera rotundifolia, which does not mean there is no risk, so it is advisable to consult a doctor or pharmacist before starting to use it, especially if you are taking other medicines. The same caution applies to combining it with other cough syrups or remedies and to formulas that include licorice, a plant that calls for care in people with high blood pressure or who take diuretics and corticosteroids.

Historical Notes and Interesting Facts

Small and intriguing, Drosera rotundifolia has gathered many curiosities throughout its history. The genus name, Drosera, comes from the Greek droserós, “dewy”, derived from drósos, “dew”, and alludes to the shiny, sticky droplets covering the leaves, which resemble morning dew and can trap unwary insects, an adaptation that lets the plant thrive in nutrient-poor soils.

One of the species’ greatest enthusiasts was the naturalist Charles Darwin, who devoted a good part of the research gathered in his 1875 book Insectivorous Plants to it, documenting carnivorous behavior in the plant kingdom through careful experiments. Darwin was fascinated by the sundew’s ability to attract, capture and digest insects, a phenomenon that challenged the botanical ideas of his time, and his detailed observations contributed greatly to the understanding of carnivorous plant biology.

In the Middle Ages, the sundew was surrounded by mysticism and folk beliefs, and the droplets on its leaves were seen as a “dew of youth” or “dew of virility”, which is why the plant went into potions that promised to slow aging. There are also records of a peculiar culinary use in parts of Scandinavia, where the enzymes secreted by the leaves are said to have been used to curdle milk for cheesemaking, a custom that shows the place this small plant held in popular culture.

Today, since wild populations are protected in several European countries, obtaining good-quality raw material has become a research topic, and a 2024 study proposed quality parameters for Drosera rotundifolia as a medicinal plant, while another, from 2025, evaluated extracts of the species in the laboratory as inhibitors of Escherichia coli biofilm, including toxicity tests.

Frequently Asked Questions about Sundew

Is Sundew Safe to Consume?

At usual doses and for short periods, Drosera rotundifolia is generally considered well tolerated by adults, whether in herbal or homeopathic preparations. Its naphthoquinone content, however, discourages prolonged internal use or high doses, and use should be stopped in case of gastric irritation. Pregnant or breastfeeding women, parents of young children and people taking other medicines should consult a health professional before using the plant.

What Are the Main Traditional Uses of Sundew?

Sundew is traditionally valued for respiratory problems and appears in records of use for dry and spasmodic cough, bronchitis, laryngitis and throat irritation, as well as historical uses in asthma and whooping cough. The expectorant, antispasmodic, anti-inflammatory and mucolytic properties attributed to it explain this traditional use, but robust clinical studies are still lacking, and diseases such as asthma and whooping cough require medical follow-up.

How Does Sundew Catch Insects?

Drosera rotundifolia has a highly specialized trapping mechanism, based on leaves covered with small glandular tentacles that secrete a sticky, glistening substance resembling dewdrops. Drawn by this secretion, insects land on the leaves and get stuck, and the leaves then slowly curl to enfold the prey. The plant releases digestive enzymes and absorbs the insect’s nutrients, supplementing the nutrition it obtains from poor soils.

Can I Grow Sundew at Home?

Yes, Drosera rotundifolia can be grown at home, provided the conditions of its habitat are reproduced, with a humid environment, an acidic substrate and plenty of sunlight. A mix of peat and sand kept constantly moist is commonly used, and the plant needs a winter dormancy period, which should be simulated to keep its life cycle healthy. Choose nursery-grown plants, because collecting from the wild threatens wild populations that are protected in several countries.

Which Parts of the Plant Are Used in Herbal Medicine?

Traditionally, the plant is used whole, with a focus on the aerial parts, that is, the leaves and flowers, which hold most of the bioactive compounds studied. Harvesting should be done sustainably, both to preserve the species and to ensure the quality of the plant material.

Why Avoid Prolonged Use of Sundew?

Sundew contains naphthoquinones, such as plumbagin, which in excess can irritate the mucous membranes, so the recommendation is to avoid prolonged internal use or high doses. Ideally, the plant should be used for short periods, at a dose set by a health professional, and use should be stopped at the first sign of gastric irritation. During pregnancy and breastfeeding and in young children, the plant should only be used with professional guidance.