Pondweed Family

(Potamogetonaceae)

Identification of pondweed species is notoriously difficult because structural differences among species are often small (e.g., clasping-leaf and whitestem pondweeds), environmental factors often influence the growth form of a species, and hybridization between species is common (e.g., variable and whitestem pondweeds).  The growth form of a species may be related to current velocity, depth, clarity, temperature of water, time of year, nutrients, bottom type, etc.

Hybridization between species often results in an intermediate form that has some characteristics of both species and is, therefore, difficult to identify.

Some characteristics useful in identifying pondweeds include:  1) all pondweeds have leaves scattered singly on the stems, especially on older portions of the plant;  2) some species may have floating leaves that look different (Figure 4a) than submersed leaves;  3) all pondweed leaves have a midrib; however, this characteristic may be difficult to see, especially on narrow-leaf pondweeds;  and 4) some species have a prominent sheath and/or stipule at the base of each leaf (Figure 4b).

Pondweeds are among the most important waterfowl foods in the United States.

Figure 4.    Characteristics of pondweeds;  (a) whole plant, and (b) stem and leaf.