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Zannichellia palustris

L.

Horned Pondweed

G5Secure Found in 6 roadless areas NatureServe Explorer →
G5SecureGlobal Rank
Least concernIUCN
UnknownThreat Impact
Identity
Unique IDELEMENT_GLOBAL.2.147401
Element CodePMZAN03010
Record TypeSPECIES
ClassificationSpecies
Classification StatusStandard
Name CategoryVascular Plant
IUCNLeast concern
Endemicoccurs (regularly, as a native taxon) in multiple nations
KingdomPlantae
PhylumAnthophyta
ClassMonocotyledoneae
OrderNajadales
FamilyPotamogetonaceae
GenusZannichellia
Other Common Names
horned pondweed (EN) Zannichellie des marais (FR)
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.
Conservation Status
Rank Method Rank calculation - Biotics v2
Review Date2024-11-01
Change Date1984-10-03
Edition Date2024-11-01
Edition AuthorsN. Ventrella (2024)
Threat ImpactUnknown
Range Extent>2,500,000 square km (greater than 1,000,000 square miles)
Number of Occurrences> 300
Rank Reasons
Zannichellia palustris is a widespread perennial or annual aquatic forb occurring in brackish and fresh waters of streams, estuaries, and lakes of North and South America, Mexico, the West Indies, Africa, Australia, and Eurasia. There are over 1,500 occurrences of this species, which are threatened by development, recreational activities, invasive species, erosion, pollution and eutrophication, and likely other threats in some places. Little is known about trends, but with a large range extent and high number of occurrences, Zannichellia palustris is considered secure.
Range Extent Comments
Zannichellia palustris is an extremely widespread species, occurring nearly worldwide, in North and South America, Mexico, the West Indies, Africa, Australia, and Eurasia (FNA 2000, POWO 2024). In North America, it occurs throughout Alaska, Canada, and the United States, though its distribution in South Carolina is doubtful (FNA 2000, Weakley and the Southeastern Flora Team 2024). Range extent was estimated using herbarium specimens and photo-based observations documented between 1993 and 2024 (GBIF 2024, iNaturalist 2024, SEINet 2024).
Occurrences Comments
By applying a 1 km separation distance to herbarium records and photo-based observations documented between 1993 and 2024, there are estimated to be more than 1,500 occurrences rangewide (GBIF 2024, iNaturalist 2024, SEINet 2024).
Threat Impact Comments
Threats to Zannichellia palustris are not widely documented but include development, recreational activities, invasive species, erosion, pollution and eutrophication, and likely other threats in some places (NatureServe 2024). There is insufficient data, including anecdotal accounts, to understand the scope and severity of threats for this taxon. However, their overall impact is likely negligible given the species' broad range, large number of occurrences, tolerance of light disturbance, and affinity for typically abundant habitats, as well as no obvious intrinsic vulnerabilities.
Ecology & Habitat

Habitat

In North America, Zannichellia palustris occurs in a range of freshwater to brackish environments, including backwaters, bogs, marshes, streams, lakes, estuaries, and various water bodies at elevations from -55 to 3100 m (FNA 2000, Les 2020). It occurs in full sunlight and prefers harder substrates, tending not to occur on substrates with significant peat or muck accumulation. This species can tolerate high salinity and turbidity, and often grows in shallow waters of less than 1 m (Les 2020).

Reproduction

Seed production is prolific, with high densities recorded (Les 2020). Seeds are non-buoyant and rely on water currents for dispersal, accumulating in sediment banks, especially via tidal activity. Germination is influenced by temperature and salinity, with seeds remaining viable for extended periods when dry.
Palustrine Habitats
HERBACEOUS WETLANDFORESTED WETLANDBog/fen
Other Nations (2)
CanadaN5
ProvinceRankNative
SaskatchewanS4Yes
Nova ScotiaS4Yes
QuebecS4Yes
New BrunswickS4Yes
NunavutSUYes
Island of NewfoundlandS2Yes
OntarioS4Yes
Prince Edward IslandS3Yes
ManitobaS3Yes
Yukon TerritoryS2Yes
Northwest TerritoriesSHYes
AlbertaS3Yes
British ColumbiaS5Yes
United StatesN5
ProvinceRankNative
ArkansasS2Yes
MontanaS4Yes
KansasS5Yes
ColoradoS4Yes
District of ColumbiaSNRYes
New HampshireS1Yes
AlaskaSNRYes
OklahomaSNRYes
KentuckyS4Yes
North CarolinaS2Yes
WyomingS3Yes
GeorgiaSNRYes
MinnesotaSNRYes
VirginiaS5Yes
LouisianaSNRYes
MichiganSNRYes
MassachusettsSNRYes
North DakotaSNRYes
WashingtonSNRYes
South DakotaSNRYes
Rhode IslandSNRYes
TennesseeSNRYes
IllinoisS3Yes
MarylandSNRYes
VermontS1Yes
TexasSNRYes
MississippiSNRYes
New JerseyS4Yes
IndianaS5Yes
West VirginiaS1Yes
New MexicoSNRYes
AlabamaSNRYes
New YorkS5Yes
ArizonaSNRYes
CaliforniaSNRYes
UtahSNRYes
NebraskaSNRYes
MissouriS3Yes
PennsylvaniaS4Yes
MaineS2Yes
FloridaSNRYes
NevadaS3Yes
WisconsinSNRYes
OhioSNRYes
IdahoSNRYes
IowaS4Yes
DelawareS2Yes
ConnecticutS4Yes
OregonSNRYes
Threat Assessments
ThreatScopeSeverityTiming
1 - Residential & commercial developmentUnknownUnknownUnknown
6 - Human intrusions & disturbanceUnknownUnknownUnknown
6.1 - Recreational activitiesUnknownUnknownUnknown
8 - Invasive & other problematic species, genes & diseasesUnknownUnknownUnknown
8.1 - Invasive non-native/alien species/diseasesUnknownUnknownUnknown
8.1.1 - Unspecified speciesUnknownUnknownUnknown
9 - PollutionUnknownUnknownUnknown
9.3 - Agricultural & forestry effluentsUnknownUnknownUnknown
9.3.1 - Nutrient loadsUnknownUnknownUnknown
9.3.2 - Soil erosion, sedimentationUnknownUnknownUnknown

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Plant Characteristics
DurationANNUAL, PERENNIAL
Economic Value (Genus)No
Roadless Areas (6)
Nevada (1)
AreaForestAcres
Humboldt - SouthHumboldt-Toiyabe National Forest11,152
New Mexico (1)
AreaForestAcres
Gila BoxGila National Forest23,759
Utah (4)
AreaForestAcres
418014Uinta National Forest9,683
418015Uinta National Forest17,289
418016Uinta National Forest35,240
Fishlake MountainFishlake National Forest25,217
References (9)
  1. Flora of North America Editorial Committee (FNA). 2000. Flora of North America north of Mexico. Vol. 22. Magnoliophyta: Alismatidae, Arecidae, Commelinidae (in part), and Zingiberidae. Oxford Univ. Press, New York. xxiii + 352 pp.
  2. Global Biodiversity Information Facility (GBIF). 2024. Global Biodiversity Information Facility (GBIF) data portal. Online. Available: https://www.gbif.org/ (accessed 2024).
  3. iNaturalist. 2024. Online. Available: https://www.inaturalist.org (accessed 2024).
  4. 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.
  5. Les, D. 2020. Aquatic Monocotyledons of North America: Ecology, Life History, and Systematics. CRC Press, Boca Raton, FL. 568 pp.
  6. NatureServe. 2024. NatureServe Network Biodiversity Location Data. NatureServe, Arlington, Virginia.
  7. Plants of the World Online (POWO). 2024. Plants of the World Online. Facilitated by the Royal Botanic Gardens, Kew. Online. Available: https://powo.science.kew.org/ (accessed 2024).
  8. Southwest Environmental Information Network (SEINet). 2024. Collections Databases. Online. Available: https://swbiodiversity.org/seinet/collections/index.php (accessed 2024).
  9. Weakley, A.S., and Southeastern Flora Team. 2024. Flora of the southeastern United States. Edition of March 4, 2024. University of North Carolina Herbarium (NCU), North Carolina Botanical Garden, University of North Carolina, Chapel Hill. 2203 pp.