AT A GLANCE
- Common Name: Round-leaved Sundew
- Scientific Name: Drosera rotundifolia
- Category: Plants
- Subcategory: Carnivorous Plants
- Range: Circumboreal across northern and temperate North America, northern and western Europe, and northern Asia to Japan
- Habitat Type: Nutrient-poor, acidic Sphagnum peat bogs, quaking wetlands, marshy heaths, and damp peaty lake margins
- IUCN Red List Status: Least Concern
- Lifespan: Perennial carnivorous herb (up to 20 to 50 years via basal rhizomes)
- Diet: Carnivorous/Autotrophic (photosynthetic, supplemented by capturing and digesting midges, mosquitoes, flies, and gnats)
- Average Size/Weight: Rosette diameter 3 to 6 cm; leaf lamina 4 to 10 mm wide; flowering scape 10 to 25 cm tall
- Key Defining Feature: Circular basal rosette of spoon-shaped leaves bristling with brilliant crimson glandular tentacles that exude glistening, sticky droplet mucilage to trap insects
Overview
The Round-leaved Sundew (Drosera rotundifolia), famously studied and admired by Charles Darwin, is one of the world’s most iconic and widespread carnivorous plants. Inhabiting acidic, nutrient-starved Sphagnum bogs across the Northern Hemisphere, this miniature botanical predator has evolved a lethal and beautiful solution to surviving in nitrogen-poor soils: it traps, suffocates, and digests live insects. Glistening in the summer sun like drops of morning dew, its sticky leaf tentacles ensnare passing gnats and midges, dissolving their bodies with powerful digestive enzymes.
Biology and Physical Characteristics
Drosera rotundifolia grows as a prostrate basal rosette hugging the damp peat surface. Each leaf consists of a long, hairy petiole terminating in a circular, disc-shaped lamina (leaf blade) 4 to 10 mm in diameter. The upper surface of the lamina is densely clothed in hundreds of specialized stalked glands (tentacles) of vivid crimson or ruby-red hue. Each tentacle is capped by a clear bead of highly viscous, mucilaginous secretion rich in acidic polysaccharides. In midsummer, it sends up a tall, slender leafless stalk (scape) bearing small, five-petaled white flowers held high above the leaves to prevent pollinators from being trapped by its sticky carnivory traps.
Behavior and Ecology
When an unwary midge or mosquito lands on a leaf, it becomes hopelessly stuck in the thick, glue-like mucilage. The insect’s violent struggles stimulate mechanoreceptors, triggering an electrical action potential that causes neighboring tentacles to bend inward toward the prey within minutes. The entire leaf blade slowly curls around the insect, sealing it into a temporary digestive cup. The glands then secrete a potent cocktail of digestive enzymes—including proteases, acid phosphatases, and esterases—that break down the soft tissues of the insect, allowing the plant to absorb precious nitrogen, phosphorus, and mineral nutrients directly into its leaf cells over several days.
Conservation and Human Impact
The Round-leaved Sundew is classified as Least Concern on the IUCN Red List, supported by its immense circumpolar distribution across vast northern boreal peatlands. However, southern populations in Central and Western Europe and the contiguous United States have suffered extensive declines from peat extraction, wetland drainage for agriculture, commercial forestry, and atmospheric nitrogen deposition, which alters bog chemistry and allows competing grasses to overgrow the sundew.
Interesting Factoid
Charles Darwin was so mesmerized by the Round-leaved Sundew that he wrote, ‘I care more about Drosera than the origin of all species in the world,’ conducting extensive experiments proving its tentacles could detect the weight of a tiny human hair.