The paths and open firebreaks of the Crousa Downs are a good place to look for Round-leaved Sundew in the summer.
Photo: Steve Townsend
Scientific name: Drosera rotundifolia
Other names: Common Sundew
Conservation status: IUCN – least concern
Round-leaved Sundew is very widespread, with a distribution that includes northern Europe, Canada, Korea and Japan. It is found on wet acid heaths or in bogs, where it is often associated with Sphagnum ssp. In Britain, it is the most common of the three native sundew species: the others are Oblong-leaved Sundew (D. intermedia) and Great Sundew (D. anglica), the last of which has been assessed as a nationally threatened species.
Like most other Sundews (Droceraceae), Round-leaved Sundew is a perennial insectivorous plant. It is dormant over the winter, protected from the cold by tightly folded leaves, before emerging in the spring, generally then flowering from June to August. The hairless flower stalk contrasts with the hairy leaf stalks, and is usually between 10 and 15 cm tall, with small white flowers which open in sunshine. The plants leaves form a rosette, and are very distinctive with their sticky red glandular hairs (the sticky substance is called mucilage). The leaves of our other two sundews are relatively narrow, but the circular-shaped leaves of the Round-leaved Sundew give the plant its common name.
Insects are attracted to sundews by the sugary mucilage and red colour of the leaf hairs. Once stuck, the leaf close over the insect and the plant secretes enzymes to digest its prey. Once the process is complete, the leaf opens up again. This insectivory has probably evolved in response to the nutrient-poor nature of the sundews’ acid habitat. The insects they digest provide supplementary nutrients, including ammonia, which is a source of nitrogen.
Did you know…?
…the drops of mucilage on the glandular leaf hairs glisten in sunlight like dew, giving sundews their common genus name
…each sundew plant can consume as many as 2000 insects in a single season
…Round-leaved Sundew can hybridise naturally with Great Sundew (Drosera anglica) and Oblong-leaved Sundew (D. intermedia)
More information and references:
Bates, R. and Scolding, B., 2002. Wild Flowers of The Lizard. Cornwall County Council, Cornwall.
Rose, F. and O’Reilly, C., 2006. The Wild Flower Key, 2nd edition. Frederick Warne, London.
Stace, C., 2010. New Flora of the British Isles, 3rd edition. Cambridge University Press, Cambridge.
Published: July 2013
Author: Amanda Scott
Photos: Steve Townsend