Sundew

Statema, B. C. P.

Plant

Sundew

Round-leaved sundew, dew plant, red rot, youth-wort, Rosa Solis; Herba rosellae, Sonnenthau rosollis, Rosée du Soleil; Drosera rotundifolia L.

Known today as: Drosera rotundifolia, of the family Droseraceae, a small insectivorous perennial of peaty bogs and the muddy edges of ponds and rivers. Its round leaves lie flat on the ground, covered with long red sticky hairs, each tipped with a gland whose fluid “looks like a dewdrop, hence its name,” Grieve writes. The hairs curve slowly inward on any insect that alights, and the glands then secrete a fluid that digests it. The small white flowers open only in sunshine. The flowering plant, dried in the air, is the drug.
Kind: Plant, in 1 older authority
Constituents: quercetin, hyperoside, citric acid
Earliest authority here: Culpeper, The Complete Herbal (1653) (1616–1654)
In other databases: Plants of the World Online · GBIF · Wikidata

Caution. Culpeper records that the leaves raise blisters on the skin, and Grieve calls the juice acrid and caustic. None of the sources read for this entry reports on its safety when taken.

Sundew: what was it used for?

A remedy for coughs and the lungs. Culpeper held its distilled water in wine good for consumption and “all other diseases of the lungs, as phthisicks, wheezings, shortness of breath, or the cough.” Grieve records it as used with advantage in whooping cough, early consumption, chronic bronchitis, and asthma; she adds that the juice was said to take away corns and warts and could curdle milk.

Sundew: what does modern science say?

No European monograph for it was found for this entry. A 2022 laboratory study, noting that sundew extracts are traditionally used for cough during a common cold, found that an extract and its flavonoids relaxed the airway muscle of mouse tracheal slices and increased the beating of their cilia; it was not a study in people, and the searches of Europe PMC made for this entry found no clinical trial of sundew alone.

Pharmacognosy & Toxicology

Constituents

quercetin ChEMBLa flavonoid that, in a 2022 laboratory study, raised the beating of the airway cilia
hyperoside ChEMBLwith 2″-O-galloylhyperoside, among the flavonoids that relaxed airway muscle
citric acidwith malic acid, in the juice, by Grieve’s account

Mechanism

In mouse tracheal slices an extract relaxed the airway muscle and quickened the cilia; quercetin and 2″-O-galloylhyperoside inhibited the enzymes PDE1A and PDE4D. Not a study in people.

Standing

There is no European monograph, and no clinical trial of sundew alone was found for this entry.

Grieve, M. A Modern Herbal, “Sundew.” As published on botanical.com. Read in full · the text read
Hake A, et al. (2022). Effects of Extracts and Flavonoids from <i>Drosera rotundifolia</i> L. on Ciliary Beat Frequency and Murine Airway Smooth Muscle. Molecules (Basel, Switzerland). PMID 36235159. Abstract read · the text read

The abstract of each source, beneath its citation. For Club members. About the Club or sign in.

Constituent names open the compound’s record at PubChem, and “ChEMBL” beside a name opens its record at ChEMBL, the European Bioinformatics Institute’s database of bioactive molecules. Where a mechanism line was checked against ChEMBL (ChEMBL 37, read 1 October 2026), the check is shown with the measured value and its source paper, or says plainly that nothing has been measured. Doses are as the references give them, for description only; this is not medical advice. Each source carries the result of its check against Crossref, PubMed, or the authority’s page: see Verification.

Sundew: what lore surrounds it?

Grieve reports that in America it had been advocated as a cure for old age.

Sundew: what did the older authorities say?

Culpeper, The Complete Herbal (1653): Culpeper puts it under the Sun and the sign Cancer, and observes that its leaves are moist even on the hottest day: “the hotter the sun shines on them, the moister they are.” The leaves laid on the skin raise blisters, “which has caused some to think it dangerous to be taken inwardly,” but he answered that other things which draw blisters are not dangerous to take, and noted a common drink of it with aqua vitae and spices, used for qualms and passions of the heart.

Sources

Grieve, M. A Modern Herbal, “Sundew.” As published on botanical.com. Read in full · the text read
Culpeper, N. The Complete Herbal, “ROSA SOLIS, OR SUN DEW.” Project Gutenberg, 49513. Read in part · the text read
Hake A, et al. (2022). Effects of Extracts and Flavonoids from <i>Drosera rotundifolia</i> L. on Ciliary Beat Frequency and Murine Airway Smooth Muscle. Molecules (Basel, Switzerland). PMID 36235159. Abstract read · the text read

Verification

Checked

October 1, 2026

Passes

Every sentence read against its sources, in the pass over the remaining 343 entries
The Standing line checked against the authority it names (EMA, WHO, FDA, CITES, Commission E)
Every dated or regulatory claim checked by category across the database

Sources

3 cited: 1 read in full, 1 read in part, 1 abstract read. 1 with the abstract on file.

Corrections

None were needed.

What was checked, how, and what was found is set out on the Verification page. A checked source is one whose record was found; it does not make the entry medical advice.

Club members can point at a technical term in this entry, such as a constituent, an action, or a word of Jung’s, to read its definition from the source. The Club.

Cite This Entry

Version 1 · first published October 17, 2026

Chicago: “Sundew.” In Materia Medica, edited by B. C. P. Statema. Version 1. The Thinking Press, 2026–. Last modified October 17, 2026. https://thethinkingpress.org/materia-medica/sundew.
MLA: “Sundew.” Materia Medica, edited by B. C. P. Statema, version 1, The Thinking Press, 17 Oct. 2026, thethinkingpress.org/materia-medica/sundew. Accessed 17 Oct. 2026.
APA: Sundew. (2026, October 17). In B. C. P. Statema (Ed.), Materia medica (Version 1). The Thinking Press. Retrieved October 17, 2026, from https://thethinkingpress.org/materia-medica/sundew

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Sundew

Sundew: what was it used for?

Sundew: what does modern science say?

Pharmacognosy & Toxicology

Sundew: what lore surrounds it?

Sundew: what did the older authorities say?

Sources

Verification

Cite This Entry

See Also

Sharing quercetin, hyperoside, citric acid

Also in Nicholas Culpeper

Drawing on the same sources: Grieve, Culpeper

Nearby in the alphabet