This submerged aquatic plant consists of branching leafy stems up to
2½' (0.75 m.) long. The slender stems are about 1 mm. across; they are
pale green or pale yellowish green, glabrous, somewhat flattened, and
flexible. Alternate leaves occur along unbranched areas of the stems,
while either alternate or opposite leaves occur where the stems divide.
These leaves are up
to 6 cm. long (rarely longer) and about 1.5 mm. across (varying from
1.0-2.0 mm. across). The leaves are green or olive green, linear in
shape, smooth along their margins, glabrous, and sessile, tapering to
flat acute tips. The leaves are grassy in appearance, relatively soft,
and flexible, lacking glands. Fused stipules occur at the leaf bases
that are 8-20 mm. long and usually early-deciduous. Submerged floral
spikes develop from some of the leaf axils on short peduncles. These
floral spikes are 2-6 mm. long and up to 4 mm. across, each one
consisting of a short dense cluster of flowers that is spherical to
short-cylindrical in shape. Each flower is about 2 mm. across,
consisting 4 green to greenish brown sepals (or sepaloid connectives),
4 stamens, and 4 pistils. The sepals are clawed (contract abruptly) at
their bases. The peduncles are 3-12 mm. long and about 1 mm. across;
they are pale green or pale yellowish green and somewhat flattened.
blooming period occurs during mid- to late summer, lasting about 3
weeks for a colony of plants. The flowers are cross-pollinated
by water currents. Afterwards, fertile flowers are replaced by achenes
(up to 4 achenes per flower). These achenes are 1.25-2.25 mm. long and
1.00-1.75 mm. across; they are green to brownish
green, ovoid-globoid in shape, somewhat flattened,
smooth-sided, short-beaked, and keeled. The sharp keels of these
achenes are winged and crested (appearing toothed). The bases of some
achenes may have a minute tooth-like projection. This aquatic plant
also produces narrow turions (winter buds) that are up to
1 cm. long and 2 mm. across. The root system is fibrous. Sometimes
fibrous roots develop from the lower nodes of stems that are decumbent
on bottom sediment. This aquatic plant can spread vegetatively from the
leafy stems that drift in water to new areas.
The preference is full sun, shallow clear water that is
stagnant or slow-moving, and bottom sediment containing silt,
organic matter. Desirable water pH can be mildly acidic to alkaline.
Leafy Pondweed (Potamogeton
) can spread aggressively in some wetlands.
pondweed will decline in abundance when it occurs in water that is too
muddy from suspended sediments, or that contains too much fertilizer
(e.g., nitrogen and phosphorus) from agricultural or suburban run-off.
The latter problem can cause excessive competition from filamentous
Range & Habitat:
Leafy Pondweed (Potamogeton foliosus
is common in most areas of
Illinois (see Distribution
), where it is native. This pondweed is
widely distributed in North America. Habitats consist of spring-fed
streams, slow-moving creeks, ponds, sheltered areas of lakes, drainage
canals, and ditches that contain water during most of the year. This
pondweed adapts to shallow water better than most pondweed species
and it is often common in disturbed wetland
habitats, particularly when there is protection from waterfowl or fish.
The larvae of some shore flies (Ephydridae),
, feed on the
submerged leaves of this pondweed, as do the larvae of Parapoynx
(Watermilfoil Leafcutter Moth). Larvae of the
feed on the submerged stems and roots of
various pondweeds (Potamogeton
). Because of its soft fine foliage
and relative abundance, Leafy Pondweed is one of the more important
sources of food for vertebrate animals among the various pondweeds.
Both the seeds and foliage are eaten by many ducks, geese, and swans
(see Waterfowl Table
are also eaten by carp, catfish, and other kinds of fish (see Forbes,
1888), and they are eaten by such turtles as Chelydra serpentina
(Snapping Turtle), Chrysemys
(Painted Turtle), Emydoidea
(Blanding's Turtle), Graptemys ouachitensis
(False Map Turtle), Sternotherus
(Musk Turtle), and Trachemys scripta
(Slider); see Lagler
(1943) and Ernest et al. (1994). Muskrats also feed on these plants
(Hamerstrom & Blake, 1939; Martin et al., 1951/1961).
Because Leafy Pondweed often forms dense mats of leafy stems, it
provides good cover for minnows, aquatic insects, and other aquatic
Photographed plants were collected
from a ditch in Savoy, Illinois.
This common pondweed has a rather grassy appearance.
It can be difficult to distinguish Leafy Pondweed (Potamogeton foliosus
from other submerged
) with linear leaves unless the floral
spikes are present. Compared to these species, the floral spikes of
Leafy Pondweed are very short and densely flowered, and they have
shorter peduncles (3-12 mm.). In addition, the leaves of Leafy Pondweed
usually lack visible glands and its stems are flattened, rather than
terete. The achenes of this pondweed are also distinctive because of
their winged crested keels, which are visible to the naked eye.
Different varieties of Leafy Pondweed have been described across its
geographic range, although they tend to intergrade. In Illinois, it is
the typical variety (Potamogeton
) that is commonly encountered.