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 is also found on New Guinea.
The leaves of the common sundew are arranged in a basal rosette. The narrow, hairy 1.3-5 centimetre long petioles support 4-10 millimetres long laminae. The upper surface of the lamina is densely covered with red glandular hairs that secrete a sticky mucilage (see Carnivory section, below).
A typical plant has a diameter of around 3-5 centimetres, with a 5-25 centimetre 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 1-1.5 mm light brown seeds that are slender and tapered.
In the winter, D. rotundifolia produces a hibernaculum in order 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, that cover its leaves. It has evolved this carnivorous behaviour in response to its habitat, which is usually poor in nutrients or so acidic that nutrient availability is severely decreased. The plant uses enzymes to dissolve the insects - which become stuck to the glandular tentacles - and extract nitrates and other nutrients from their bodies.
In North America, the common sundew is found in all parts of Canada except the Canadian Prairies and the tundra regions, southern Alaska, the Pacific Northwest, and along the Appalachian Mountains south to Georgia and Louisiana.
It is found in much of Europe, including the British Isles, most of France, the Benelux nations, Germany, Denmark, Switzerland, Czech Republic, Poland, Belarus, the Baltic countries, Sweden and Finland, as well as northern portions of Portugal, Spain, Romania and Iceland and southern regions of Norway and Greenland. It is infrequent in Austria and Hungary, and some populations are scattered around the Balkans.
In the UK, this is the most common form of sundew and can be found on Exmoor, Dartmoor, Sedgemoor, the Lake District, Shropshire, and Pennines in Scotland. It is usually found in bogs, marshes and in hollows or corries on the side of mountains.
In Asia, it is found across Siberia and Japan, as well as parts of Turkey, the Caucasus region, the Kamchatka Peninsula and southern parts of Korea. Populations can also be found on the island of New Guinea.
The common sundew thrives in wetlands such as marshes and fens. It is also found in wet stands of black spruce, Sphagnum bogs, silty and boggy shorelines and wet sands. It prefers open, sunny or partly sunny habitats.
The round leaved sundew is classified as "Least concern" in the IUCN red list. In North America, the roundleaf sundew is considered endangered in the U.S. states of Illinois and Iowa, exploitably vulnerable in New York and threatened in Tennessee. 
According to D.H. Hall, et al., Drosera rotundifolia plant extracts show great efficacy as an anti-inflammatory and anti-spasmodic, more so than D. madagascariensis, as a result of the flavonoids such as hyperoside, quercetin and isoquercetin, but not the naphthoquinones present in the extracts. The flavonoids are thought to affect the M3 muscarinic receptors in smooth muscle, causing the antispasmodic effects. Ellagic acid in D. rotundifolia extracts has also been shown to have anti-angiogenic effects.
- ^ Regents of the University of California (1993). The Jepson Manual: Higher Plants of California. Berkley, California: University of California Press. http://ucjeps.berkeley.edu/cgi-bin/get_JM_treatment.pl?3427,3428,3430.
- ^ Paper DH, Karall E, Kremser M, Krenn L (April 2005). "Comparison of the antiinflammatory effects of Drosera rotundifolia and Drosera madagascariensis in the HET-CAM assay". Phytotherapy Research 19 (4): 323–6. doi:10.1002/ptr.1666. PMID 16041727.
- ^ Krenn L, Beyer G, Pertz HH, et al. (2004). "In vitro antispasmodic and anti-inflammatory effects of Drosera rotundifolia". Arzneimittelforschung 54 (7): 402–5. PMID 15344845.
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- Karen Legasy, Shayna LaBelle-Beadman and Brenda Chambers. (1995). Forest Plants of Northeastern Ontario. Ontario: Lone Pine Publishing.
- (Swedish) Den virtuella floran - Rundsileshår. Naturhistoriska riksmuseet, 1997. Accessed 31 May, 2005.