BC Conservation Data Centre: Species Summary
Potamogeton gramineus
grass-leaved pondweed
| Scientific Name: | Potamogeton gramineus L. | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| English Name: | grass-leaved pondweed | ||||||||||
| Classification / Taxonomy | |||||||||||
| Scientific Name - Concept Reference: | Kartesz, J.T. 1994. A synonymized checklist of the vascular flora of the United States, Canada, and Greenland. 2nd edition. 2 vols. Timber Press, Portland, OR. | ||||||||||
| Classification Level: | Species | ||||||||||
| Species Group: | Vascular Plant | ||||||||||
| Species Code: | POTAGRA | ||||||||||
|
|||||||||||
| Conservation Status / Legal Designation | |||||||||||
| Global Status: | G5 (Sep 2024) | ||||||||||
| Provincial Status: | S5 (Apr 2019) | ||||||||||
| BC List: | Yellow | ||||||||||
| Provincial FRPA list: | |||||||||||
| Provincial Wildlife Act: | |||||||||||
| COSEWIC Status: | |||||||||||
| SARA Schedule: | |||||||||||
| General Status Canada: | 4 - Secure (2010) | ||||||||||
| Ecology & Life History | |||||||||||
| General Description: | |||||||||||
| Technical Description: | Rhizome buff, often suffused or spotted with red, variable in thickness. Stem much branched, terete 0.5-1.0 mm in diam; stele with the oblong type pattern with but one central bundle (rarely with 2) and usually but 1 lateral bundle on each side; endodermis of 4-cells strongly thickened on the inner and lateral faces; interlacunar bundles strongly developed but only in the outer interlacunar circle; subepidermal bundles present or absent; pseudo-hypodermis absent or about 1 cell thick. Submersed leaves linear to lance-linear or lance-elliptical (sometimes oblanceolate), 1-9 (-13) cm long, 0.1-1 (-1.5) cm wide, tapering gradually to a sessile base; apex acute, usually sharp pointed; nerves 3-9 (-11); lacunae of 1 or 2 rows along midrib, mostly obscure; margins with fugacious 1-celled translucent denticles. Floating leaves coreaceous, blades ovate to elliptical (rarely subrotund) 1.5-5 (-7) cm long 1-2 (-3) cm wide; apex obtuse or bluntly mucronate: base cuneate or rounded; petioles 2-10 (-15) cm long, mostly longer than the blades; nerves 3-17 (-23); lacunae obscure. Peduncles at base about same thickness as stem, sometimes clavate 2-10 (30) cm long. Spikes in anthesis usually rather compact, of 5-10 whorls of flowers; in fruit cylindric and crowded, 1-2.5 cm long 0.6-0.8 cm thick. Flowers sessile or on peduncles up to .5 mm long; sepaloid connectives orbicular to oval, blades (.7-) 1.2-1.6 (-2.3) mm wide, claws (.2-) .4-.8 (-1) mm long; anthers oblong .6-1 (-1.1) mm long. Fruits mostly obovate, 1.7-2.5 (-2.8) mm long (excluding beak) (1.4-) 1.6-2 (-2.3) mm wide, keels usually strongly evident, but often obscured by the loose exocarp, beak facial, short and curved toward the back; exocarp usually loose green or rarely tawny; endocarp with keels low and obutse, beak linear and weak, .3-.5 mm long, loop solid; apex of seed pointing .3-.7 mm above the basal end. A variable species characterized by a stem with many lateral compound branches bearing numerous small leaves (Ogden 1943). | ||||||||||
| Diagnostic Characteristics: | Stem terete or slightly flattened, not black spotted. Many submersed leaves more than 4 mm wide, 3-8 cm long, with 3-9 veins, sessile, not cordate or auriculate at the base. Stipular sheath 1-3 cm long. Beak of the achene less than 1.5 mm long and lacking a basal appendage. Plants not red tinged. | ||||||||||
| Similar Species: | |||||||||||
| Global Ecology Comments: | This species is extremely variable in size and shape fluctuation, which may be due to differences in depth and velocity of the waters in which it grows. | ||||||||||
| Habitats: (Type / Subtype / Dependence) |
|||||||||||
| Global Habitat Comments: | Potamogeton gramineus occurs in a variety of aquatic habitat types, including "backwaters, bays (shallow), canals (irrigation), channels, coves (shallow), ditches (roadside), fens, flats (tidal), floodplains, lagoons, lakes (bog, kettle, oxbow), pannes (calcareous, interdunal), ponds (beaver, boggy, drying, glacial, kettle, sag, stock), pools (brook, meadow, muskeg, river, roadside), potholes, rivers, sloughs, streams (outlet), and tanks (cattle)" (Les 2020). It thrives in full sun, but it also tolerates low light levels. It occurs in water depths from 0.15 to 6 m, though it is more common in shallow waters. Most populations of this species are found in northern sites with clear water, low sediment nutrient levels, and a short growing season. | ||||||||||
| Provincial Phenology: (1st half of month/ 2nd half of month) |
|||||||||||
| Elevation (m) (min / max): | Provincial: | ||||||||||
| Known Pests: | |||||||||||
| Pollen Vector: |
ABIOTIC
Water Wind |
||||||||||
| Pollinator: | |||||||||||
| Dispersal: |
ABIOTIC
BIOTIC Birds Water |
||||||||||
| Provincial Inventory | |||||||||||
| Inventory Priority: | |||||||||||
| Ownership of occurrences (Known locations): | |||||||||||
| Inventory Need: | |||||||||||
| Economic Attributes | |||||||||||
| Distribution | |||||||||||
| Endemic: | N | ||||||||||
| Global Range Comment: | Potamogeton gramineus has a circumboreal global distribution (POWO 2024). In North America, it occurs throughout Alaska and all of Canada, south to California, east to New Mexico, north to Colorado, east through Maryland, and north to Maine in the United States (FNA 2000). Range extent was estimated to be over 76 million square kilometers using herbarium specimens and photo-based observations documented between 1993 and 2024 (GBIF 2024, iNaturalist 2024, SEINet 2024). | ||||||||||
| Disjunct, more common elsewhere: | |||||||||||
| Peripheral, major distribution elsewhere: | |||||||||||
| Authors / Contributors | |||||||||||
| Global Information Author: | ISAAC, J., rev. N. Ventrella (2024) | ||||||||||
| Last Updated: | Sep 27, 2024 | ||||||||||
| Provincial Information Author: | |||||||||||
| Last Updated: | |||||||||||
| Last Literature Search: | |||||||||||
| References and Related Literature | |||||||||||
Les, D. 2020. Aquatic Monocotyledons of North America: Ecology, Life History, and Systematics. CRC Press, Boca Raton, FL. 568 pp. |
|||||||||||
Ogden, E. C. 1943. The broad-leaved species of Potamogeton of North America north of Mexico. Rhodora 45:57-105, 19-163, 171-214. |
|||||||||||
Please visit the website Conservation Status Ranks for definitions of the data fields used in this summary report.
Suggested Citation:
B.C. Conservation Data Centre. 2024. Species Summary: Potamogeton gramineus. B.C. Minist. of Environment. Available: https://a100.gov.bc.ca/pub/eswp/ (accessed Jun 9, 2026).