Hydrilla verticillata

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Legend for Species Pages

waterthyme, hydrilla

Hydrilla verticillata (L. f.) Royle
  • Occurrence in Alberta – N
  • Global Invasive Species Database –
  • NatureServe Rank – High
  • Haber, Upland –
  • Haber, Wetland –
  • CWF, Status & Invasive Range –
  • Alberta Revegetation Guidelines – N
  • The Nature Conservancy –
  • CBCN –
  • AB Weed – N


This native Elodia canadensis is similar to Hydrilla. Photo: Richard Old, XID Services

Hydrilla was reported as occurring in Beauvais Lake in 2011, due to misidentification. Native Elodea species (see photo) are similar, but lack rhizomes or stolons. Hydrilla is not known to occur in Canada. North American distribution: AL, AZ, CA, CT, DC, DE, FL, GA, IA, LA, MD, ME, MS, NC, PA, SC, TN, TX, VA, & WA. Listed as noxious, in the most restrictive category available, in the majority of these jurisdictions.

Freshwater aquatic, reproduces by seed and vegetatively via turions, first introduced into the US in 1960, used commercially in the aquarium trade, native of Africa. Crowds out native vegetation where it is established. In more northern locations sometimes associated with hot springs and warmer water.

Identification: download USDA NRCS Invasive Species ID Sheet: [1].


USDA Plants Profile [2]

USDA Invasive Species Profile [3]

eFloras.org, Flora of North America [4], Vol 22, Elodea.

Map references

sample: Map data for T. ramosissima