Round-leaved sundew (Drosera rotundifolia, L. 1753)

Identity

Round-leaved sundew (Drosera rotundifolia L., 1753), also known as Roundleaf sundew or Common sundew, is a small carnivorous perennial in the Droseraceae family. Carl Linnaeus described it in 1753, making it one of the earliest carnivorous plants formally named. Charles Darwin devoted most of his experiments on plant carnivory, published in Insectivorous Plants in 1875, to this species rather than any other, including the Venus flytrap. ^{1 3}

The genus name Drosera comes from ancient Greek drosos, meaning “dew,” and describes the shining mucilage droplets on the tentacles, visible even in dry, sunny weather. The English name sundew evokes the same appearance. Its French name rossolis derives from medieval Latin ros solis, “dew of the sun.” The plant also gave its name to a southern European liqueur made since the Middle Ages; the later Italian word rosolio lost that botanical connection. ²

Recognition

A basal rosette carries round leaf blades, 4–10 mm (0.16–0.39 in) across, on slender, hairy petioles 1.3–5 cm (0.5–2 in) long. Red tentacles cover the upper surface, each ending in a gland that secretes sweet, sticky mucilage to attract and trap small insects. The whole rosette generally measures 3–5 cm (1.2–2 in) across. ^{3 2}

An upright, leafless flower stalk, 5–25 cm (2–10 in) tall, holds the flowers well above the sticky foliage, keeping pollinating insects away from the plant’s own traps. The white or pink flowers have five petals and measure 1.25 cm (0.5 in) across or less. They produce slender, tapered, light-brown seeds 1–1.5 mm (0.04–0.06 in) long. ^{3 6}

Winter survival depends on a hibernaculum, a bud of tightly curled leaves at ground level that replaces the summer foliage during cold weather. A rosette turning black in fall may therefore be entering dormancy rather than dying. ⁶

Useful taxonomy

More than 150 species belong to Drosera, but three similar species often share European bogs. Leaf shape is easier to check in the field than flowers or seeds, which are absent outside their season. Drosera rotundifolia has a round blade and a European range wider than those of its two relatives combined. Drosera anglica Huds. has an elongated, narrow blade, while Drosera intermedia Hayne has a spoon-shaped blade. These species sometimes hybridize: Drosera × obovata Mert. & W.D.J.Koch is the sterile natural cross between D. rotundifolia and D. anglica. None replaces Drosera rotundifolia as the accepted name published by Linnaeus in 1753. ¹

Habitat and range

Across its circumboreal range, Drosera rotundifolia occupies one of the widest distributions in the genus. It occurs through almost all of Europe, Siberia, much of North America (Canada except the Prairies and tundra, southern Alaska, the Pacific Northwest and the Appalachians south to Georgia and Louisiana), Japan and Korea. Isolated populations also reach Turkey, the Caucasus, Kamchatka, New Guinea and the Philippines (Mindanao). ^{6 3}

Acidic sphagnum bogs, marshes and fens are its main habitat, along with waterlogged sandy shores and open black spruce swamp woodland. It needs abundant light and soil poor in nitrogen and phosphorus, without lime or fertilizer. ⁶

Within France, the species occurs outside the Mediterranean fringe but is restricted to bogs, an increasingly rare lowland habitat. National protection prohibits destruction, transport and sale of any part of the plant there. Drainage can dry a bog’s acidic substrate within a few years, causing sundew to disappear. Globally, the IUCN lists it as Least Concern, although some U.S. states, including Illinois, Iowa and Tennessee, consider it locally threatened. ^{7 5 8}

Life cycle and reproduction

An insect attracted to the sweet mucilage becomes stuck on a tentacle. Neighboring tentacles gradually bend toward it, while digestive enzymes dissolve its soft tissues over several days. The plant mainly extracts ammonia and available nitrogen, scarce in peat soil. Research also shows it can take nutrients from the soil when available: carnivory supplements its nutrition rather than being an absolute dependency. ³

Summer flowers develop on the upright stalk above the rosette. Seeds fall near the parent and germinate in 4–8 weeks on damp sphagnum at about 20 °C (68 °F). In cultivation, dividing established rosettes yields identical plants within a season; leaf and root cuttings can also be taken during active growth. ^{6 4}

Uses and risks

Cultivated Round-leaved sundew is primarily ornamental, grown in artificial bogs, terrariums or pots standing in water, alongside living sphagnum. No toxic compound is recorded for this species, and it does not appear on lists of plants poisonous to domestic animals. ⁴

Extracts containing flavonoids such as hyperoside and quercetin were long used in herbal medicine as antispasmodics and expectorants for coughs, chronic bronchitis and asthma; the digestive secretion was also used on warts. That medicinal reputation encouraged intensive wild collection across Europe, weakening natural populations long before legal protection was introduced. ^{4 8}

Varieties, look-alikes and related plants

Specialist growers mainly offer Charles Darwin, selected to grow without strict winter dormancy and easier to maintain year-round than wild-origin plants. Forma comosa, with branched flower stalks and more flowers, remains uncommon and circulates mainly among North American collectors. Neither changes the botanical identity of the species. ⁴

Bog companions most likely to cause confusion are Drosera anglica and Drosera intermedia, described above, which may also hybridize with D. rotundifolia. Common cranberry (Vaccinium oxycoccos) shares its peat-bog habitat but traps no insects and draws nitrogen directly from the peat. The more widely sold Venus flytrap, Dionaea muscipula, catches prey by actively closing its lobes; sundew relies on sticky mucilage without rapid movement. ⁶

Main sources

• Plants of the World Online / Kew, Drosera rotundifolia L.
• Royal Horticultural Society, Drosera rotundifolia - round-leaved sundew
• Encyclopaedia Britannica, Roundleaf sundew
• Plants For A Future, Drosera rotundifolia
• IUCN Red List, Drosera rotundifolia assessment (2016)
• US Forest Service FEIS, Drosera rotundifolia species review
• INPN / MNHN, Drosera rotundifolia - round-leaved sundew
• Parcs nationaux de France, Le drosera à feuilles rondes (Drosera rotundifolia); original page archived 21 May 2026