Round-leaved Sundew (Drosera rotundifolia)

Round-leaved Sundew Plants on Dead Tree Stump

Round-leaved Sundew (Drosera rotundifolia), also known as the Common Sundew, is an emergent, carnivorous, perennial forb found in wetlands, marshes and on the shores of ponds and lakes.3,6,9 The plants shown on this page were found growing on rotting tree stumps in French Hill Pond. The Round-leaved Sundew is in the Sundew Family (Droseraceae) and order Nepenthales (North American classification)6 or Caryophyllates (European classification)9. The family and genus names are from the Greek for "dewy."10 The species name is from the Latin for "rounded." There is one other Sundew that may be found on Mount Desert Island: Spatulate-leaved Sundew (Drosera intermedia).4 The Spatulate-leaved Sundew has elongated, spoon-like leaves, longer than narrow.2

The green, rounded leaves are about 1/6 to 2/5 inches (4 to 10 millimeters) long on stalks (petioles) up to two inches (5 centimeters) long. The stalks are hairy and grow in a basal-rosette pattern.3,5,9 The top part of the leaf is covered with sticky, red hairs. When an insect comes in contact with the upper part of the leaf, it will be entrapped by the hairs and the leaf excretes enzymes to extract nutrients for the plant from the insect.3,5,10

The flowers grow in one-sided clusters of 2 to 15 individual flowers on slender, hairless stalks from the middle of the plant base. The white to pink flowers are about ¼ inch (6 millimeters) wide and have five petals.5 The seeds are about 0.04 of an inch (one millimeter) long, light brown and tapered.5,9,10

Sundew Buds

The root system is simple and horizontal. During the first year of growth, this plant will have a tap root and be immature.3

This plant blooms from June to August.5

The photograph above shows numerous Sundew plants. Few insects would survive an encounter with these plants. The tiny flowers of this plant are barely discernable among the leaves. However, the distinctive and prominent leaves make identification of this plant easy and definitive. The next photograph shows a single Sundew plant.

Single Round-leaved Sundew Plant

Note the shallow root system in the next photograph.

Single Sundew Plant

The following photograph shows the top of a Round-leaved Sundew leaf. As an insect lands on this leaf, the red hairs stick to the insect entrapping it. The pressure of the struggling insect will cause the leaf hairs and leaf edges to engulf the victim. The plant then secretes chemicals from the hairs that will extract nutrients from the insect. The process of digestion can be longer than four days.10

Round-leaved Sundew Top Leaf

The bottom of a leaf, shown in the photograph below, is smooth, green and virtually hairless.

Round-leaved Sundew Bottom Leaf

The next microphotograph is a close-up of the leaf edge showing the hair connections.

Sundew leaf edge

The following microphotograph shows the surface of a leaf without the hairs. The red arrows point to stomata, the openings in the leaf that allow the leaf to breath. These openings can open and close to allow carbon dioxide into the leaf for photosynthesis and allow oxygen to escape to the atmosphere. A stoma (singular of stomata) will close if the plant is threatened by rain and other unwanted contaminates.

Sundew leaf surface

The following microphotograph shows an individual stoma near the center of the microphotograph above.

Sundew leaf stoma

An enlargement of the stoma in the above microphotograph allows a better determination of the stoma's size. The stoma is the elliptical hole in the middle and is about 10.4 micrometers along the major axis of the ellipse. The elliptical vacuole, the dark area surrounding the stoma, is about 20 micrometers along the major axis of the ellipse. The guard cell surrounding the vacuole has a major axis of about 40 micrometers. Please keep in mind that these parts of the leaf are three-dimensional, that is raised above the surface of the leaf. The microphotograph does not show the three-dimensional aspect making any measurements approximate. Of interest is the fact that the lengths of the major axes of these leaf parts roughly form a geometric progression with a common factor of two. That is, the major axis of the vacuole is about twice the length of the stoma and the major axis of the guard cell is about twice the length of the vacuole.

Sundew leaf stoma closeup

The following microphotograph shows the tip of a leaf hair. The bright red hair is covered with a sweet, sticky mucilage. Most plant leaves are covered with a mucilage but the mucilage is much less sticky than the Sundew mucilage. Insects are attracted to the sundew by the bright red color and the sweet mucilage. Few insects can pry themselves out of the grasp of these sticky hairs. Ants are strong enough to extract themselves before they are consumed by the plant. The sweet mucilage attracts ants but ants are useful to the plant by removing the remains of insects that the plant has killed and from which the plant extracts fluids.3

Sundew hair tip

The following microphotograph is a section of a hair stem. Note the long and round cells. Some of these cells excrete an enzyme that reacts with the fluids in captured insects to extract nutrients for the plant.

 

Sundew hair body

The next microphotograph shows the base of a hair and how it attaches to the leaf.

Sundew hair base

Practitioners of folk medicine may use this plant to reduce inflammation and spasms. The plant also has some antibiotic properties. The leaves will also curdle milk and can be used to make cheese.3,9

References:

1. Botanical Society of America, Carnivorous Plants, Drosera - The Sundews,  retrieved from http://botany.org/Carnivorous_Plants/Drosera.php, 06/15/2016

2. Connecticut Botanical Society, Spatulate-leaved Sundew (Spoon-leaved Sundew) retrieved from  http://www.ct-botanical-society.org/Plants/view/179, 06/20/2016

3. Encyclopedia of Life, Drosera rotundifolia,  retrieved from http://eol.org/pages/593301/details, 06/19/2016

4. Mittelhauser, Glen H., Gregory, Linda, Rooney, Sally C. and Weber, Jill E., The Plants of Acadia National Park, The University of Maine Press, Orono, Maine, 2010, page 163

5. Niering, William A.,Olmstead, Nancy C., The Audubon Society Field Guide to North American Flowers, Alfred A/ Knopf, New York, 1988, page 495.

6. United States Department of Agriculture, Plants Database, Drosera rotundfolia, retrieved from  http://plants.usda.gov/core/profile?symbol=DRRO, 06/15/2016

7. United States Department of Agriculture, Forestry Service Database, Matthews, Robin F., 1994, Drosera rotundfolia, retrieved from  http://www.fs.fed.us/database/feis/plants/forb/drorot/all.html. 06/19/2016

8. United States National Plant Germplasm System, Taxon: Drosera rotundfolia L., retrieved from https://npgsweb.ars-grin.gov/gringlobal/taxonomydetail.aspx?400172, 06/15/2016

9. Wikipedia, the free encyclopedia, Drosera rotundfolia, retrieved from https://en.wikipedia.org/wiki/Drosera_rotundifolia, 06/15/2016

10. Wildflower.org, Drosera rotundfolia, retrieved from http://www.wildflower.org/plants/result.php?id_plant=DRRO, 06/15/2016

 

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