Potamogeton foliosus (Leafy Pondweed)

Plant Info
Also known as:
Genus:Potamogeton
Family:Potamogetonaceae (Pondweed)
Life cycle:perennial
Origin:native
Habitat:part shade, sun; shallow water; lakes, ponds, slow-moving streams and rivers
Bloom season:June - September
Plant height:2 to 30 inches
Wetland Indicator Status:GP: OBL MW: OBL NCNE: OBL
MN county distribution (click map to enlarge):Minnesota county distribution map
National distribution (click map to enlarge):National distribution map

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Detailed Information

Flower: Flower shape: 4-petals Flower shape: indistinct Cluster type: spike

[photo of spike coming into bloom] Short, head-like cluster held above or below the surface of the water, only about ¼ inch (6 mm) long, arising from some leaf axils on branching stems. Spikes have 2 or 3 whorls of flowers, each flower with a 4-parted style surrounded by 4 stamens, each stamen with a green to brownish, ladle-shaped, sepal-like appendage.

Leaves and stems: Leaf attachment: alternate Leaf type: simple

[photo of leaf tip and veins] Leaves are all submersed and more or less spirally arranged along the stem; no floating leaves are produced. Blades are flexible, usually light green to olive or sometimes reddish, linear, ½ to 3¼ inches (to 8.2 cm) long, .3 to 2.3 mm wide, pointed at the tip, toothless, not wavy along the edges. The midvein is prominent and usually flanked by 1 pair of lateral veins, occasionally none or 2; 1 or 2 narrow rows of large, empty cells (known as the lacunar band) may be along the midvein but are usually absent.

[photo of stipule and glandless leaf nodes] Leaf bases are stalkless, not clasping, and rarely have a pair of glands at the node. At the base of the leaf is a pale, membranous appendage (stipule), not connected to the leaf blade, often rolled around the stem with overlapping edges (convolute), blunt at the tip, not usually shredding, less than 1 inch (to 22 mm) long, greenish to brown, rarely white. Stems are slightly compressed and may frequently branch. Vegetative buds (turions), also known as winter buds, are narrowly cylindric, develop later in the summer at branch tips or some leaf axils, but are uncommon.

Fruit: Fruit type: seed without plume

[photo of fruit cluster] Fruit is a dry seed (achene), olive to brown when mature.

[photo of achenes] Achenes are irregularly oval to nearly round, 1.5 to 2.7 mm long with a prominent, knobby keel along the back edge. The beak is erect, .2 to .6 mm long.

Notes:

Leafy Pondweed is common throughout Minnesota, usually found in the quiet or slow-flowing waters of lakes, ponds and rivers, usually with a sandy, mucky or silty bottom and in less than 4 feet of water.

This is one of several Pondweeds with no floating leaves and linear, submersed leaves, the widest between 1 and 4 mm wide, but is the only one in Minnesota that lacks glands at the leaf nodes, has pointed leaf tips, and achenes have a prominent, knobby keel. There are 2 recognized subspecies: subsp. fibrillosus is an uncommon western species with stipules that shred into fibers, frequently has glands at leaf nodes, achenes have a less prominent keel and beak shorter than .2 mm; subsp. foliosus is found across North America and is as described above.

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More photos

Photos by K. Chayka taken in Anoka County. Photos by Peter M. Dziuk taken in Anoka, Aitkin and Becker counties.

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