Plants of the genus Drosera are carnivorous with leaf surfaces covered with glandular hairs. They have worldwide distribution. Roundleaf Sundew is a native perennial plant forming a rosette of leaves near the surface.
Leaves are held either erect or prostrate. Leaf stalks are 1.5 to 5 cm long with a round to sub-round leaf that is usually no more than 1 cm long and 1.2 cm wide (broader than long.) The leaves have stipules which are fused to the leaf stalk. The entire rosette is usually only 5 cm (2 inches) wide. The leaf margin is without lobes but it has reddish erect glandular hair and the inner surface has finer glandular hair all of which secrete a sticky substance which traps insects. The leaves of the Drosera genus are not hinged and do not snap shut like those of the Dionaea genus.
The inflorescence is a multi-flowered erect bare scape rising from the center of the rosette, having from 2 to 15 flowers. The flowers occur on one side of the scape which is two to 10 inches long.
Flowers are 5-parted, to 1/2 inch wide, with 5 small sepals and 5 petals. Petals range in color from white to pink. There are 5 stamens.
Seed: Flowers can be pollinated by wind or self pollination. They mature to a small 5 mm long capsule which contains light brown small seeds which are light and contain an air pocket - a 'testa,' which allows them to float. .
Habitat: Roundleaf Sundew is found in bogs, swamps, fens and other very moist areas. They survive winters by forming an over-wintering bud of tightly coiled leaves - a structure known as a hibernaculum. Sun and cool temperatures are optimal as the plant survives in boreal zones around the world. Shade will not allow the plant to flower.
The secretions from the glands on the leaves contain a sugary substance to attract insects and then a secretion of enzymes digest the insect. This process provides some needed nutrients for a plant which grows in a nutrient scarce environment. The bright color of the leaves has little to do with attracting insects according some recent studies. [i.e. Foot, Rice and Millett, Biology Letters, 16 April, 2014.] See also Eloise Butler's text below the photos.
Names: The genus Drosera is from the Greek drŏsĕrŏs meaning 'dewy' as in the dewy appearance of the glandular tips hairs on the leaf. The species rotundifolia means 'round-leaved.' The author name for the plant classification - 'L.' refers to Carl Linnaeus (1707-1778), Swedish botanist and the developer of the binomial nomenclature of modern taxonomy. Eloise Butler explains the common name in her notes below the photos.
Similar plant or comparisons: Four other species of Sundew are found in Minnesota. D.anglica, the English Sundew; D. intermedia, the spoon-leaf sundew ;D. linearis, the slender-leaf sundew; and D. X obovata, the obovate-leaved sundew. The latter has only been collected once in one place. The others are differentiated by their leaf shape; except that only D. linearis has leaf stipules free of the stalk.
Above: A cluster of rosettes of Roundleaf Sundew. Drawing from Britton, N.L., and A. Brown. 1913. An illustrated flora of the northern United States, Canada and the British Possessions. 3 vols. Charles Scribner's Sons, New York.
Below: 1st photo - The leaf margin is without lobes but it has reddish erect glandular hair and the inner surface has finer glandular hair all of which secrete a sticky substance which traps insects. 2nd photo - The white flower on the tall leafless scape. Photo Merle R. Black, Wisconsin Flora.
Notes: Roundleaf Sundew is indigenous to the Garden. Eloise Butler noted its presence on Sept. 20, 1908. She planted it frequently - 1921, '24, '27, '31 and '32. Plants in 1921 and 1931 came from Isle Royal, 1924 from the Quaking Bog, 1927 from Northern Minnesota and 1932 from Sarona Wisconsin. Martha Crone still reported it on her 1951 census but it was lost sometime after that.
Roundleaf Sundew in Minnesota is found in most counties in the northern and northeastern part of the state and then southward in the eastern half of the state to the Metro area. In North America it is widespread across all the Canadian provinces and the northern tier of states in the U.S. and southward in the eastern states.
Eloise Butler wrote: The motile, sensitive hairs on the leaves are tipped with glands resembling dewdrops; but which, unlike dew, do not disappear under the influence of the sun, –hence the name, sundew. The leaf is a first-class fly-trap, and the glistening glands contain an active, digestive principle. When a thirsty insect lights on a leaf, the hairs bend over it and firmly grasp it; the more the insect struggles, the tighter it is held; more and more hairs entangle it, and finally the whole leaf rounds over it. The fluid in the globules then oozes out and digests the victim. ["Bulletin of the Minnesota Academy of Science" Volume 5 No. 1, 1911.]
References: Plant characteristics are generally from sources 1A, 32, W2, W3, W7 & W8 plus others as specifically applied. Distribution principally from W1, W2 and 28C. Planting history generally from 1, 4 & 4a. Other sources by specific reference. See Reference List for details.
Identification booklet for most of the flowering forbs and small flowering shrubs of the Eloise Butler Wildflower Garden. Details Here.
Friends of the Wild Flower Garden, Inc. Text and photos are by G. D. Bebeau unless otherwise credited. "www.friendsofthewildflowergarden.org"