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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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Update: June 2012
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