Forest County Cooperative Extension -

One of the enjoyable parts of a landscape can be a pond. Many people put a pond on their property, and then are surprised by some of the problems that can occur as the pond matures. One of the problems faced by pond owners can be the overgowth of aquatic plants of various kinds.

Aquatic plants are not all bad - in fact they are often very good. They add oxygen to the water, making the pond more suitable for fish and other aquatic animal life. They also are a surface area that small organisms such as algae, aquatic insects and other small organisms can utilize, and those animals provide a food source for larger animals. They also are hiding places and nurseries for other animals. Aquatic plants also can reduce wave action, and thus help to stabilize shorelines, reducing erosion and increasing the water clarity. They absorb nutrients and other forms of pollution, improving the water quality of the pond. They add diversity and structure to the pond bottom for visual appeal. They are also food for fish, waterbirds, and other animals.

With all of that, why should anyone be interested in controlling aquatic plants?

For one thing, some plants are noxious weeds. Several species of plants have been imported into the United States, many of them for use in the aquarium trade. When these weeds are released into the wild, they have no predators and can out-compete the native plants of the region.

In other cases, the plants become overly abundant, crowding the pond with vegetation and making it difficult to use the pond for the purpose that was intended.

Overly abundant plants may also cover water bodies and wetlands, preventing oxygenation and "suffocating" fish and other animals. They may prevent the use of water bodies for fishing swimming, and other recreation. They can disrupt navigation, slow or even stop water flow, disrupting flood control and irrigation systems. Thay may also interfere with fish production or harvest, reduce the effectiveness of predator fish in controlling prey fish populations.

There are several methods to control aquatic vegetation, but to do it properly, you should know what type of vegetation is in your pond, and what are the best methods of control.

Identifying a pond plant may be very difficult. There are few easy references to help identify pond plants, and these plants are often not included in weed identification references. If you collect a good specimen, you may be able to find some assistance in identification from your Extension agent, the Natural Resources Conservation Service, or your local University botany department.

A good specimen contains several qualities. It will have all of the leaf shapes that the plant contains. Many aquatic plants may have one leaf form under water, and another leaf form when it emerges from the water.

A good specimen will also contain some flowering or fruiting bodies. While these may be difficult to find, they often make identification much more accurate.

Your pond may contain several types of aquatic plants, including a wide variety of major groups. Algae, ferns, mosses, and flowering plants may all be found in aquatic environments. Relatively few ferns and mosses create problems in ponds in our area, though.

Algae can be a significant problem in many types of ponds. They can cause odors in the water, reducing its palatability for livestock. They may also restrict recreational uses, and certainly cut down on the visual appeal of the pond. Most algae that cause these problems are classified in the general category of filamentous algae, but some others can also cause problems.

Two common algae that cause problems look like flowering plants. They have parts that look like stems, roots and leaves. However, most treatments for aquatic plants will not affect these algae, known as Nitelia and Chara. Some of the most common treatments for algae will not control them either.
Another major group of aquatic plants are the submersed plants. These plants grow under the water, for the most part. Some of them can grow through the water, and produce some leaves and flowers above the water surface. In most cases, the leaves that are produced above the water will look different from those below the water.

Submersed aquatic plants may require different chemical treatments than emergent aquatic plants. Other methods of control may also be of more or less use, depending on the growth habit of the plant. Many of the aggressive imported plants that cause problems in waterways fall into the submersed group.

Many of the submersed plants have the ability to form new plants from small pieces of themselves. As a result, just raking the plants up from the bottom is not an effective method of control, since the plants will just re-root in some other spots. The plants must be physically removed from the pond area.

Emergent aquatic plants include floating-leaved plants such as American lotus and water lily. They also include plants where the entire plant floats on the surface such as watermeal and duckweed, and plants that are rooted in the soil and have leaves that are mainly out of the water, such as cattails.

With these plants as well, it is important that the identity be known. Some noxious weeds may require more aggressive measures than other weeds. Some weeds may have some properties that make them more suitable to your pond than others.

Pond management can be a benefit to your land use, a great hobby, or a frustration. The best way to keep the pond working to your benefit is to monitor the pond, and try to catch problems before they get out of control. Knowing the plants that are in your pond is just one part of that monitoring.

There are several good references to help you identify pond plants. Some of the commonly controlled aquatic plants are pictured in the Penn State Cooperative Extension publication titled "Pond Management and Aquatic Plant Control", available for $4 from your local Penn State Cooperative Extension office.

Additional information can be obtained from other sources, including several web sites. A couple of useful ones are:

Ohio Pond Management - Bulletin 374-99, Ohio St. Extension
http://ohioline.ag.ohio-state.edu/b374/

Center for Aquatic and Invasive Plants,U. of Fla.
http://aquat1.ifas.ufl.edu/
Has some excellent graphics of many common aquatic plants, as well as a wide variety of materials on invasive plants. Some common plants of the Northeast U.S. are not on this site, and many of the ones listed on the site do not occur in the Northeast, due to climate differences. A very useful source of information on a wide variety of aquatic plant topics.

Virginia Cooperative Extension
http://www.ppws.vt.edu/scott/weed_id/aquatics.htm
contains graphics of common aquatic weeds from .

Available on alternative media upon request
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