Washington Flora Checklist
A Checklist of the Vascular Plants of Washington State
Hosted by the University of Washington Herbarium


Checklist » Potamogetonaceae
Potamogetonaceae   (Pondweed Family)

Notes: FNA22: "The family has historically been considered to consist of two genera, Potamogeton and Groenlandia. Recent molecular evidence (D. H. Les, unpublished), combined with existing morphologic evidence, indicates that Potamogeton in the broad sense actually represents two separate lineages. We recognize those lineages at the generic level, Potamogeton in the strict sense and Stuckenia. Consequently, we accept three genera in the family, Potamogeton, Stuckenia, and Groenlandia.

Reproductive features are most important in separating species of Potamogeton (R. R. Haynes 1978), and we include the entire family here. The keys may not always utilize reproductive features, but they are based on fruiting individuals. We strongly recommend that no one collect specimens of Potamogetonaceae that are lacking reproductive structures.

Leaves of Potamogetonaceae are stipulate. The stipules form a tubular sheath (stipular sheath) around the stem, free from or adnate to the base of the blade. In some species the leaf and sheath of submersed leaves are adnate for part of their length, and the leaf appears to have a sheathing base with an adaxial ligule at the junction of sheath and blade or petiole.

Fruits of Potamogetonaceae are drupaceous. The fruits do have endocarps but do not have fleshy mesocarps. Mesocarps exist but never become fleshy. Consequently, the fruits are not true drupes, they are drupaceous.

Many species of Potamogetonaceae undergo extensive vegetative reproduction either by turions or stem fragmentation. Turions are excellent modes of vegetative reproduction. The structures are produced at the stem tips and eventually fall to the substrate, either by a portion of the stem breaking off or by the stem itself falling to the substrate. The turions survive an unfavorable season, germinate, and grow into new plants during the next growing season. Because the unfavorable season is usually winter in North America, turions have been called "winter buds." At least one species, Potamogeton crispus, produces turions in early summer, and the turions survive the unfavorable season (summer, in this instance), germinating in the fall. The plant then survives the winter as a young individual, only a few centimeters long, even under ice, and begins growth as the water warms in the following spring. "Winter bud" is certainly not the correct term for P. crispus. The term "turions" designates all such structures, regardless of the unfavorable season."

Family Synonyms:
» Zannichelliaceae (Horned-Pondweed Family)

» Campbell, D. H. 1897. A morphological study of Naias and Zannichellia. Proc. Calif. Acad. Sci., ser. 3, 1: 1--70.

Haynes, R. R. and L. B. Holm-Nielsen. 1987. The Zannichelliaceae in the southeastern United States. J. Arnold Arbor. 68: 259--268.

Posluszny, U. and P. B. Tomlinson. 1977. Morphology and development of floral shoots and organs in certain Zannichelliaceae. Bot. J. Linn. Soc. 75: 21--46.

Taylor, N. 1909. Zannichelliaceae. In: N. L. Britton et al., eds. 1905+. North American Flora.... 47+ vols. New York. Vol. 17, pp. 13--27.

Tomlinson, P. B. and U. Posluszny. 1976. Generic limits in the Zannichelliaceae (sensu Dumortier). Taxon 25: 273--279.

Family treatment authored by Peter F. Zika; last updated 4/6/2009 by David Giblin
Taxon (native species in boldface) # Synonyms Common Names
Potamogeton alpinus Balb.   [FNA22, H&C] 5 northern or reddish pondweed
Potamogeton amplifolius Tuck.   [FNA22, H&C] 0 large-leaved or broad-leaved pondweed
Potamogeton crispus L.   [FNA22, H&C] 0 curly pondweed
Potamogeton epihydrus Raf.   [FNA22, H&C] 3 ribbon-leaved pondweed
Potamogeton foliosus Raf. ssp. fibrillosus (Fernald) R.R. Haynes & Hellq.   [FNA22] 2 fibrous-stipuled pondweed
Potamogeton foliosus Raf. ssp. foliosus    [FNA22] 3 leafy pondweed
Potamogeton friesii Rupr.   [FNA22, H&C] 0 flat-stalked pondweed
Potamogeton gramineus L.   [FNA22, H&C] 3 variable or grassy pondweed
Potamogeton illinoensis Morong   [FNA22, H&C] 1 illinois pondweed
Potamogeton natans L.   [FNA22, H&C] 0 floating or floating-leaved pondweed
Potamogeton ×nericus Hagstr. 0 hybrid pondweed
Potamogeton nodosus Poir.   [FNA22, H&C] 1 long-leaved or loddon's pondweed
Potamogeton obtusifolius Mert. & W.D.J. Koch   [FNA22, H&C] 0 blunt-leaved pondweed
Potamogeton praelongus Wulfen   [FNA22] 0 white-stalked or whitestem pondweed
Potamogeton pusillus L. ssp. pusillus    [FNA22] 4 small pondweed
Potamogeton pusillus L. ssp. tenuissimus (Mert. & W.D.J. Koch) R.R. Haynes & Hellq.   [FNA22] 6 Berchtold's pondweed
Potamogeton richardsonii (A. Benn.) Rydb.   [FNA22, H&C] 2 clasping-leaved or Richardson's pondweed
Potamogeton robbinsii Oakes   [FNA22, H&C] 0 Robbin's or fern pondweed
Potamogeton strictifolius A. Benn.   [Draft Revised H&C] 1 narrowleaf pondweed
Potamogeton zosteriformis Fernald   [FNA22, H&C] 1 eel-grass or flat-stem pondweed
Stuckenia filiformis (Pers.) BÃœrner ssp. alpina (Blytt) R.R. Haynes, Les & M. Kral   [FNA22] 8
Stuckenia filiformis (Pers.) Börner ssp. occidentalis (J. W. Robbins) R. R. Haynes, Les & M. Kral   [FNA22] 3 threadleaf-pondweed
Stuckenia pectinata (L.) Boerner   [FNA22] 1 sago-pondweed
Stuckenia vaginata (Turczaninow) Holub   [FNA22] 1 bigsheath-pondweed
Zannichellia palustris L.   [FNA22, H&C] 1 horned pondweed

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