Hydrocotyle (ranunculoides, umbellata) Herbaceous Alliance
Mats of floating pennywort

USDA Ecological Section Map

Summary Information

  • Primary Life FormHerb
  • Elevation0-150 m
  • State RarityS3?
  • Global RarityG4
  • DistributionCAN: BC?. USA: CA, OR?, WA?
  • Endemic to CaliforniaNo
  • Endemic to California Floristic Province and DesertsNo
  • Date Added2009/09/01

Characteristic Species

Hydrocotyle ranunculoides or Hydrocotyle umbellata is dominant or co-dominant floating on the water surface or as terrestrial herbs with Agrostis stolonifera, Argentina egedii, Bolboschoenus maritimus, Cotula coronopifolia, Eleocharis macrostachya, Festuca arundinacea, Holcus lanatus, Lemna minuta, Oenanthe sarmentosa and Schoenoplectus pungens.

Vegetation Layers

Herbs < 50 cm; cover is open to continuous.

Membership Rules

  • Hydrocotyle ranunculoides > 60% relative cover, unless Schoenoplectus pungens is present in high cover (Pickart 2006).
  • Hydrocotyle ranunculoides > 50% relative cover on the water surface of coastal lagoons, ponds, freshwater lakes, and wet marshes growing with Lemna spp. And Scirpus microcarpus (Buck-Diaz et al. 2021, Sikes et al. 2023).


Semi-permanently to permanently flooded lake margins, slow-moving streams, and mudflats surrounding pools. The USFWS Wetland Inventory (1996 national list) recognizes Hydrocotyle ranunculoides and H. umbellata as OBL plants.

Other Habitat, Alliance and Community Groupings

MCV (1995) Not treated
NVCS (2009) Hydrocotyle umbellata permanently flooded herbaceous alliance
Calveg Tule-Cattail, Water
Holland Coastal and valley freshwater marsh
Munz Freshwater marsh
WHR Fresh emergent wetland
CDFW CA Code 52.117.00

National Vegetation Classification Hierarchy

Formation Class Hydromorphic Vegetation (Aquatic Vegetation)
Formation Subclass Freshwater Aquatic Vegetation
Formation Freshwater Aquatic Vegetation
Division North American Freshwater Aquatic Vegetation
Macro Group Western North American Freshwater Aquatic Vegetation
Group Temperate Pacific freshwater aquatic bed