Forest Preserve District of Cook County, Illinois
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Pondweeds
Nature Bulletin No. 317-A   October 19, 1968
Forest Preserve District of Cook County
Richard B Ogilvie, President
Roland F. Eisenbeis, Supt. of Conservation

PONDWEEDS
There are three common types of aquatic plants in our lakes, ponds, and sloughs. One includes the conspicuous cattails, burreeds, rushes, arrowheads and similar plants which are rooted n the shallow water or wet ground along the shores. They have leafy stems rising above the surface. Another includes those plants which have no anchoring roots and float freely in or on the water: the algae, the tiny duckweeds, the hornwort or coontail, and the bladderwort. The third type is composed of plants which are anchored to the bottom by their roots and have leaves which either float on the surface, like the water lilies, or are submerged like most of the pondweeds.

The true pondweeds and a number of other plants with similar habits, thrive in shallow lakes, ponds, sloughs, bays and streams where they root on the bottom and stretch upward like underwater gardens. If the water is clear enough for a light to penetrate, some kinds nourish in depths of ten to twenty feet. Since all except the primitive Chara or Muskgrass are flowering plants, they must push their blossoms above the surface long enough to be pollinated and set seed. All but the Chara have soft pliable stems that sway with the waves and are buoyed up by air-filled cells in the stems or leaves. Most kinds live in fresh water, some in brackish water, and a few in sea water.

Of the 65 species of true pondweeds known in the temperate parts of the world, more than half are found in the United States where they are the dominant group of seed-bearing aquatic plants, especially in the New England and Great Lakes regions. Some are large, with broad oval floating leaves, while others have delicate thread-like leaves. Some have both. All are relished by many kinds of wildlife -- ducks, coots, geese, swans, shorebirds, muskrats, beaver, deer and moose. They furnish food or homes for hosts of aquatic insects, worms, snails, leeches and small shrimps that serve as food for fish.

The Sago Pondweed is perhaps the most important species as duck food because it produces large crops of little nut-like seeds and, at the base of the plant, numerous starchy tubers which they also seek. They eat all parts of the Naiad or Bushy Pondweed which is very abundant and may rival the Sago in our region. Other important typical kinds are the Floating-leaf and the Ruffle-leaf pondweeds. Widgeon Grass is partial to alkaline and brackish waters, and all parts are eaten by waterfowl. Along the Atlantic coast, the mainstay for brant and many ducks is the marine Eelgrass which sometimes chokes the shallows with its long tape-like leaves. It is also gathered, dried, and used for packing soft- shelled crabs or to stuff upholstery. During the early 1930's it was almost wiped out by a fungous disease and the wildfowl suffered, but it is now coming back. The freshwater eelgrass or Wild Celery is a choice food for canvasback and other diving ducks.

Pondweeds, coontail, milfoil and other submerged water plants can be both good and bad. They provide food and hiding places for young fish but, when overly abundant, allow too many of them to escape the larger predatory fish -- with the result that the fish become overcrowded and stunted. In many places, pondweeds become so thick and tangled that an angler finds his hook fouled with bunches of them. Wads of them wind up on motorboat propellers and it may even become difficult to row. Bathing beaches may become clogged with pondweeds. Worst of all, in shallow waters, they rot under the ice in winter and may so completely use up the oxygen that most fish suffocate.

Pondweeds are like pride and prosperity, you can have too much.


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