Hydrocotyle (ranunculoides, umbellata) Herbaceous Alliance
Mats of floating pennywort
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).
Habitats
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 |
Remarks
Hydrocotyle ranunculoides and H. umbellata are floating to terrestrial perennials with thick stolons that root at the nodes. Leaves are round to kidney-shaped, and the plants flower and fruit in summer and then die back. Leaves of H. umbellata are peltate, whereas those of H. ranunculoides are not. Both species are widespread in the northern hemisphere.
Plants create dense mats in shallow water and over wet soil. Mats can clog waterways and ditches in agriculture areas and are considered weeds under some conditions. H. ranunculoides is a noxious weed in Australia (DiTomaso and Healy 2003).
Plants create dense mats in shallow water and over wet soil. Mats can clog waterways and ditches in agriculture areas and are considered weeds under some conditions. H. ranunculoides is a noxious weed in Australia (DiTomaso and Healy 2003).
Life History Traits of the Principal Species
| Hydrocotyle ranunculoides | Hydrocotyle umbellata | |
|---|---|---|
| Life forms | Polycarpic perennial; herb | |
| Seed storage | Soil | null |
| Seed longevity | Long | null |
| Mode of dispersal | Animal; water/hydrological | null |
| Germination agents | Unknown | null |
| Mode of sprouting | Underground structures (rhizomes) | null |
| Survivability after fire/disturbance | Fire-hardy; no/low sprouter to high sprouter | null |
| Disturbance-stimulated flowering | No | null |
| Reproductive range | Life of plant | null |
| Recruitment | High | null |
| Regional variation | By species | null |
Fire Characteristics
Processes other than fire primarily disturb stands. Flooding/drying cycles are the primary processes involved in modifying stands.
| Fire return interval | — |
| Seasonality | — |
| Size/extent | — |
| Complexity | — |
| Intensity | — |
| Severity | — |
| Type | — |
| Regional knowledge | — |
Regional Status
The ranges of Hydrocotyle ranunculoides and H. umbellata include cismontane California.
- Great Valley (262Al). Stands in the Sacramento- San Joaquin River delta (Hickson and Keeler-Wolf 2007) have H. umbellata as the predominant species (Toft 2000). They are associated with open freshwater and usually adjacent to stands of Schoenoplectus acutus or Schoenoplectus californicus alliances.
- Northern California Coast (263Aa-b, Ae, Ah-k). Stands of H. ranunculoides from Humboldt Bay National Wildlife Refuge (Pickart 2006) occur in relatively freshwater to slightly brackish pools and marshy areas. Stands of H. umbellata at Point Reyes National Seashore are in coastal lagoons and freshwater lakes, including at Abbotts Lagoon and Ocean Lake (Keeler-Wolf et al. 2003a).
Management Considerations
Stands are most persistent in relatively quiet and constant freshwater wetlands. Hydrocotyle umbellata and other aquatic macrophytes can effectively remove nitrogen and phosphorus from nutrient-enriched waters such as in wastewater retention reservoirs (Reddy 1983, Reddy and DeBusk 1985).
In the Sacramento-San Joaquin River delta, native patches of H. umbellata act functionally different from invading patches of non-native Eichhornia crassipes. H. umbellata stands have more richness and abundance of native aquatic invertebrates, which are important in fish diets, as compared to E. crassipes stands with the non-native invertebrate Crangonyx floridanus, which is more common but not important in fish diets (Toft 2000, Toft et al. 2003). In the delta, the State Department of Boating and Waterways reduces floating, aquatic, non-native vegetation by herbicide application. These applications avoid Hydrocotyle patches.
Associations
- Hydrocotyle ranunculoides [1], [2], [3]
- Hydrocotyle ranunculoides - Schoenoplectus pungens [1]
References
- [1] Pickart, A.J. 2006
- [2] Buck-Diaz, J.;Sikes, K.;Evens, J.M. 2021
- [3] Sikes, K.;Buck-Diaz, J.;Vu, S.:Evens, J. 2023
- DiTomaso, J.M.;Healy, E.A. 2003