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Drosera rotundifolia (the common sundew or round-leaved sundew) is a species of sundew, a carnivorous plant often found in bogs, marshes and fens. One of the most widespread sundew species, it is generally circumboreal, being found in all of northern Europe, much of Siberia, large parts of northern North America, Korea, Japan and New Guinea.
The leaves of the common sundew are arranged in a basal rosette. The narrow, hairy, 1.3–5.0 cm long petioles support 4–10 mm long laminae. The upper surface of the lamina is densely covered with red glandular hairs that secrete a sticky mucilage.
A typical plant has a diameter of around 3-5 cm, with a 5–25 cm tall inflorescence. The flowers grow on one side of a single slender, hairless stalk that emanates from the centre of the leaf rosette. White or pink in colour, the five-petalled flowers produce 1.0–1.5 mm, light brown, slender, tapered seeds.
In the winter, D. rotundifolia produces a hibernaculum to survive the cold conditions. This consists of a bud of tightly curled leaves at ground level.
The plant feeds on insects, which are attracted to its bright red colour and its glistening drops of mucilage, loaded with a sugary substance, covering its leaves. It has evolved this carnivorous behaviour in response to its habitat, which is usually poor in nutrients or is so acidic that nutrient availability is severely decreased. The plant uses enzymes to dissolve the insects – which become stuck to the glandular tentacles – and extracts ammonia (from proteins) and other nutrients from their bodies. The ammonia replaces the nitrogen that other plants absorb from the soil.