Source: The Weeders Digest

Potamogeton crispus generally known as curly leaf pondweed is a type of aquatic plant which is commonly found in Africa, Eurasia and Australia. In the late nineteenth century, curly leaf pondweed was inadvertently introduced into the Great Lakes and inland lakes in the region of North America by the hobbyists who used this aquatic plant in their aquarium and later dumped them in various waterways. This aquatic plant was first seen in the year 1910 in Minnesota. The people of Minnesota however fail to recognize that the curly leaf pondweed is not a native aquatic plant as this aquatic plant has been in that region for many years.

It is quite easy to find the difference between the curly leaf pondweed and the other native species of aquatic plants as the color of most of the aquatic plants is green but the color of the leaves of the curly leaf pondweed is reddish green. The structure of the leaves of the curly leaf pondweed is also different from that of the other aquatic plants. The leaves of the curly leaf pondweed are about three inches that is about eight centimeter long and almost one centimeter wide, thick, oblong in shape and have wavy or undulating edges which have pointed and uneven tips. The leaves of the curly leaf pondweed is also thicker, slimmer and more slender than the other types of aquatic plants like shinning pondweed, fen pondweed, broad leaved pondweed, perfoliate pondweed and bog pondweed.

The curly leaf pondweed has branching stems which are somewhat flat and are about one to three feet long. The color of the stem of this submersed aquatic plant is reddish brown or whitish. This aquatic plant has turions in their stem tips and leaf axils but do not have any petioles. The turions and fruits of this plant come out together. The flowers of the curly leaf pondweed are short and pointed that appear on the surface of the water. These flowers can be seen on the water surface from the month of May till the month of October. The roots have stolons and rhizomes.

The curly leaf pondweed mainly reproduces from its turions which spread in the waterways by different means. Sometimes, they get carried away with the flow of the water or even they get dispersed by human activities like boating. They can also germinate from the seeds but this method of reproduction is very rare in their case. The new plants of curly leaf pondweed remain under the ice sheet in the winter and so they are the first aquatic plants to come out in the spring. Since, these aquatic plants are the first to emerge, so, they rapidly spread in the water but by early July, they die and go down to the floor of the water bodies. This unique life cycle helps in identifying the curly leaf pondweed from the other native submersed aquatic plants.

Curly leaf pondweed usually grows in the water bodies which are alkaline and have high content of nutrients in it. They are also commonly found in shallow water. This aquatic plant normally prefers low temperature of the water and low light. Because of this reason, they start germinating in the winter and come out as soon as the spring falls. However, from the mid summer, this perennial submersed aquatic plant starts dying. This characteristic of emerging in spring and dying off in mid summer is typical of the curly leaf pondweed which is not found in any other type of submersed aquatic plants. The growth of curly leaf pondweed varies from year to year. This variation in the growth of this perennial aquatic plant is due to various environmental factors such as the clearness of the water of the spring, the depth of the winter snow, etc.

The curly leaf pondweed comes out in spring and very rapidly grows in the water which forms a thick mat on the surface of the ponds, lakes and other water bodies. This formation of thick mat in the water causes a nuisance for the people as they clog the waterways. They upset the normal movement in the water. They also disturb the water recreation and boating. Even after dying in the mid summer that is in the month of July, they do not give any relief to the people as the dead curly leaf pondweed which are noxious stinking thing comes over the beach and makes it extremely unpleasant and untidy. This aquatic plant can be dangerous as this can disturb the ecological balance by taking the place of the native aquatic plants. The dead and decayed curly leaf pondweed also lowers the level of the dissolved oxygen in the water and increases the phosphorous and other nutrients in the water which in turn increase the growth of the algal blooms.

Though getting rid of the curly leaf pondweed completely is not a practical solution but it is very important to control the growth of this perennial aquatic plant because of its damaging and detrimental effects both on the environment and also on the aquatic recreation. There are several methods of preventing and controlling the growth of the curly leaf pondweed. Some of them are manual or mechanical method, chemical method, biological control method, bottom screening, etc. However, DNR permit has to be taken before treating or eradicating the curly leaf pondweed.

For controlling the spread of the curly leaf pondweed, people must make sure that all the turions that get stuck on the trailers, fishing gears, motors and boats while traveling in the water, should get removed before going to the water bodies. Manual or mechanical control method is very effective for controlling the growth of the curly leaf pondweed. Some of the mechanical control methods are hand cutting, raking and harvesting. By hand cutting and raking, these aquatic plants can be eliminated from the floor of the water while harvesting only eliminates the top five feet of these aquatic plants. There are also some herbicides that can be used to control the curly leaf pondweed. For removing these plants from ponds, these herbicides may take 2 weeks and for removing them from lakes, these chemicals may take thirty days. Some other methods of controlling the curly leaf pondweed are fall drawdown and dredging.

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Curly Leaf Pond Weed