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Illinois Pondweed

Potamogeton illinoensis

Illinois Pondweed Location in North America
Illinois Pondweed Location in Southeast US

illinois pondweed flower
illinois pondweed in sand

illinois pondweed in water

USDA, NRCS. 2018. The PLANTS Database (http://plants.usda.gov, 28 March 2018). National Plant Data Team, Greensboro, NC 27401-4901 USA.
Illustration courtesy of University of Florida/IFAS Center for Aquatic and Invasive Plants. Used with permission.

What is Illinois Pondweed?

Physical Characteristics

Leaves:

Submersed Leaves:

  • Thin
  • Elliptical- or sword-shaped
  • Often somewhat curved
  • 8 inches long & 1.77 inches wide
  • Immobile

Floating Leaves:

  • Leather texture
  • Gradually become submersed
  • Elliptical-shaped
  • 7.5 inches long & 2.5 inches wide
  • Rounded at base
  • Often not present

Flowers:

  • Immobile
  • Oval-shaped
  • 0.05 – 0.13 inches wide
  • Small and green
  • Flowers whorled along spike
  • Spike 1 to 3 inches above water

Fruit:

  • Oval-shaped
  • 0.09 – 0.14 inches wide
  • Flat on sides
  • Top and bottom strongly developed
  • Sides less developed than top or bottom
  • Knob at base
  • Gray-green to olive-brown when mature

Stem:

  • Horizontal, underground stem
  • Spotted with red
  • Simple or branching
  • Cylindrical
  • 0.05-0.2 inches in diameter
  • Thick and fleshy

Where Does it Grow?

Illinois pondweed is a perennial plant that can be found in quiet or flowing alkaline waters of ponds, canals, lakes, streams, and rivers.

Pros and Cons of Illinois Pondweed

Illinois pondweed is utilized as food by ducks and some other types of wildlife. Submerged portions of all aquatic plants provide habitats for many micro and macro invertebrates. These invertebrates in turn are used as food by fish and other wildlife species (e.g. amphibians, reptiles, ducks, etc.). After aquatic plants die, their decomposition by bacteria and fungi provides food (called “detritus”) for many aquatic invertebrates.

How to Manage This Plant
Plant Glossary

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Photo Credits: The majority of the aquatic plant line drawings are the copyright of the University of Florida Center for Aquatic Plants (Gainsville). They are used with permission.

Aquatic plant photographs were provided by David Bayne, Jim Davis, Kelly Duffie, Billy Higginbotham, Michael Masser, John Clayton, Chetta Owens, Diane Smith, Joe Snow, Don Steinbach, Bridget Robinson Lassiter and Peter Woods.

You may use these photos, so long as you give credit to AquaPlant.

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