|Photo by John R. Gwaltney, Southeastern Flora.com|
|Division:||Magnoliophyta - Flowering plants|
|Class:||Magnoliopsida - Dicotyledons|
|Family:||Apiaceae ⁄ Umbelliferae|
|Natural range of Hydrocotyle umbellata from USDA NRCS Plants Database.|
Common names: Manyflower marshpennywort; Marsh water-pennywort
Hydrocotyle umbellata is a perennial terrestrial and aquatic species. The umbrella shaped leaves will dominate groundcover for moist soils or submerged shallow water. The leaves are peltate with veins radiating from the point of the petiole and the blades rounded with heavily notched margins. The star-shaped flowers are small with seperate petals and sepals and five stamen.
It is distinguishable from Hydrocotyle ranunculoides by having a light green disk at the location of petiole attachment while H. ranunculoides has a light pink disk.
"Glabrous perennials, rooting from the nodes of the prostrate, creeping or floating stems. Leaves solitary at the nodes, simple, peltate or cordate, orbicular to reniform, blades entire, lobed, or crenate; petioles nonsheathing. Umbels simple, branched, or verticillate; involcure much reduced or absent; flowers few or many, petals white or greenish. Fruit strongly flattened laterally, glabrous, 1-2 mm long. Carpophores absent; mericarps narrowly ovate in cross section."
"Leaves peltate, orbicular, 1-4 cm wide, crenate; petioles 4-15 (25) cm long. Umbels simple, of 15-50 pedicellate flowers, 1-2 cm broad, peduncle equaling or, more often, exceeding the length of the petioles."
Occurs from south America throughout central America and the Caribbean and along the Atlantic coast.
H. umbellata is generally found in moist areas. It is both a terrestrial and aquatic species being found in areas such as swamps, lake shores, shallow water of pond pine flats, sandy peaty ditches, shallow water of flowing streams, moist sands of open flatwoods,and floodplains. It occurs in disturbed areas such as moist roadside ditches, man made ponds, wet pastures, levees, and drainage ditches. Associated species include Eryngium prostratum, Ludwigia arcuata, Panicum hemitomon, and Bacopa.  Within areas that were recently disturbed or scoured, this species was found on exposed gravel or sand substrate.
Growth rate in terrestrial environments is double the growth rate in aquatic environments. The leaves produced in terrestrial environments differ significantly in the structure and morphology from aquatic leaves and cannot acclimate to aquatic conditions, resulting in death. In aquatic conditions, it has been observed to have an increased petiole length and larger leaves with more stomata on the upper than on the lower surface. 
Generally, this species flowers from April until September. The star shaped flowers are small and terminate in umbels. It reproduces both sexually by seed and vegetatively by growth and fragmentation of rhizomes; however, reproduce primarily by asexual reproduction (Vasseur 2005). H. umbellata has been observed flowering and fruiting March through December with peak inflorescence in May and June.
Seed bank and germination
Germination rate is higher in flooded conditions than in moist soil conditions. One study found H. umbellata evenly distributed across the seed banks of varying depths.
Various pollinators were observed to visit flowers of H. umbellata at the Archbold Biological Station. These include sweat bees from the Halictidae family (Halictus poeyi), spider wasps from the Pompilidae family (Episyron conterminus posterus), thread-wasted wasps from the Sphecidae family (Cerceris blakei, Ectemnius rufipes ais, Epinysson mellipes, Hoplisoides denticulatus denticulatus, Oxybelus emarginatus, Tachysphex apicalis and T. similis) and wasps from the Vespidae family (Leptochilus alcolhuus and Parancistrocerus salcularis rufulus).
Herbivory and toxicology
H. umbellata was found to be eaten by the Florida marsh rabbit.
Conservation, cultivation, and restoration
It is listed as endangered by the Connecticut Department of Environmental Protection as well as by the Ohio Department of Natural Resources, Division of Natural Areas and Preserves. It is also listed as extirpated by the Pennsylvania Department of Conservation and Natural Resources. It is also considered vulnerable in New York, and critically imperiled in the Canadian province Nova Scotia.
For humans, it should be noted that ingesting the leaves can cause nausea. Medicinally it is considered alexipharmic and emetic.It has often been used in folk medicine to treat skin ulcers and rheumatism.  It was also used in folk medicine for liver and kidney treatments.
References and notes
- ↑ 1.0 1.1 Weakley, A.S. 2015. Flora of the southern and mid-atlantic states. Working Draft of 21 May 2015. University of North Carolina at Chapel Hill, Chapel Hill, North Carolina.
- ↑ 2.0 2.1 [Wildflower]Accessed December 14, 2015
- ↑ 3.0 3.1 3.2 [Clemson Cooperative Extension]Accessed: December 18, 2015
- ↑ [Go Botany]Accessed: December 17, 2015
- ↑ 5.0 5.1 Radford, Albert E., Harry E. Ahles, and C. Ritchie Bell. Manual of the Vascular Flora of the Carolinas. 1964, 1968. The University of North Carolina Press. 763-4. Print.
- ↑ [Cosewic Assessment and Status Report] Accessed: December 17, 2015
- ↑ 7.0 7.1 Weakley, A. S. (2015). Flora of the Southern and Mid-Atlantic States. Chapel Hill, NC, University of North Carolina Herbarium.
- ↑ 8.0 8.1 Florida State University Robert K. Godfrey Herbarium database. URL: http://herbarium.bio.fsu.edu. Last accessed: October 2015. Collectors: Loran C. Anderson, Mel Boreham, J.P. Gillespie, Robert K. Godfrey, D.C. Hunt, Gary R. Knight, R. Komarek, R. Kral, H. Kurz, R.L. Lazor, William Lindsey, Sidney McDaniel, Herbert Monoson, William Platt, R.A. Pursell, Gwynn W. Ramsey, P.L. Redfearn Jr., J. Sincock, Cecil R. Slaughter, H. Larry Stripling, Victoria Sullivan. States and Counties: Florida: Bradford, Brevard, Citrus, Franklin,Gad Hernando, Jackson, Jefferson, Leon, Levy, Liberty, Madison, Martin, Nassau, Okaloosa, Orange, Pinellas, Putnam, Sumter, Taylor, Wakulla, Walton. Georgia: Thomas. Countries: Costa Rica, Panama. Compiled by Tall Timbers Research Station and Land Conservancy.
- ↑ Keddy, P. A. and I. C. Wisheu (1989). "Ecology, biogeography, and conservation of coastal plain plants: Some general principles from the study of Nova Scotian wetlands." Rhodora 91(865): 72-94.
- ↑ Reekie, E. G. and C. E. Dawe (2007). "The effects of flooding regime on the rare Atlantic coastal plain species Hydrocoytle umbellata." Canadian Journal of Botany 85(2): 167-174.
- ↑ Nelson, G. PanFlora: Plant data for the eastern United States with emphasis on the Southeastern Coastal Plains, Florida, and the Florida Panhandle. www.gilnelson.com/PanFlora/ Accessed: 12 DEC 2016
- ↑ Wetzel, P., A. van der Valk, et al. (2001). "Restoration of wetland vegetation on the Kissimmee River Floodplain: Potential role of seed banks." Wetlands 21(2): 189-198.
- ↑ Collins, B. and G. Wein (1995). "Seed bank and vegetation of a constructed reservoir." Wetlands 15(4): 374-385.
- ↑ Deyrup, M.A. and N.D. 2015. Database of observations of Hymenoptera visitations to flowers of plants on Archbold Biological Station, Florida, USA
- ↑ Blair, W. F. (1936). "The Florida marsh rabbit." Journal of Mammalogy 17(3): 197-207.
- ↑ USDA, NRCS. (2016). The PLANTS Database (http://plants.usda.gov, 22 May 2019). National Plant Data Team, Greensboro, NC 27401-4901 USA.
- ↑ 17.0 17.1 [] NatureServe Explorer. Accessed: May 22, 2019
- ↑ Nickell, J. M. (1911). J.M.Nickell's botanical ready reference : especially designed for druggists and physicians : containing all of the botanical drugs known up to the present time, giving their medical properties, and all of their botanical, common, pharmacopoeal and German common (in German) names. Chicago, IL, Murray & Nickell MFG. Co.
- ↑ Florentino, I. F., M. V. M. Nascimento, et al. (2013). "Evaluation of analgesic and anti-inflammatory activities of Hydrocotyle umbellata L., Araliaceae (acaricoba) in mice." Anais Da Academia Brasileira De Ciencias 85(3): 987-997.