Whorled-pennywort

Hydrocotyle verticillata Thunb.

Hydrocotyle verticillata flowers Stephen M. Young

Hydrocotyle verticillata flowers
Stephen M. Young

Class
Dicotyledoneae (Dicots)
Family
Araliaceae (Ginseng Family)
State Protection
Endangered
Listed as Endangered by New York State: in imminent danger of extirpation in New York. For animals, taking, importation, transportation, or possession is prohibited, except under license or permit. For plants, removal or damage without the consent of the landowner is prohibited.
Federal Protection
Not Listed
State Conservation Status Rank
S1
Critically Imperiled in New York - Especially vulnerable to disappearing from New York due to extreme rarity or other factors; typically 5 or fewer populations or locations in New York, very few individuals, very restricted range, very few remaining acres (or miles of stream), and/or very steep declines.
Global Conservation Status Rank
G5
Secure globally - Common in the world; widespread and abundant (but may be rare in some parts of its range).
Contents
  1. Summary
  2. Conservation and Management
  3. Habitat
  4. Range
  5. Identification Comments
  6. Taxonomy
  7. Additional Resources
  8. About This Guide

Summary

Did you know?

Heritage Botanist Steve Young discovered that some of the sites previously documented for this species were actually plants of Hydrocotyle umbellata that had produced more than one whorl of flowers thus resembling Hydrocotyle verticillata.

State Ranking Justification

There are three existing populations but only one of them is large. The other two have less than 50 plants each. There is only one other record that has not been found, from 1910 in Smithtown.

Short-term Trends

There has not been enough recent fieldwork to evaluate short-term trends. An updated is needed at the largest population.

Long-term Trends

This plant has always been rare in New York and continues to survive in only a few populations.

Conservation and Management

Threats

Succession of shrubby vegetation may be a threat depending upon water level fluctuations.

Conservation Strategies and Management Practices

Shrub encroachment on the populations should be monitored. Target shrub removal as needed to maintain the habitat.

Research Needs

Research is needed to find out whether small populations can be propagated and augmented.

Habitat

Habitat

The plants grow on the sandy or gravelly shores of large freshwater ponds.

Associated Ecological Communities

  • Coastal plain pond shore (guide)
    The gently sloping shore of a coastal plain pond with seasonally and annually fluctuating water levels. Plants growing on the pond shore vary with water levels. In dry years when water levels are low there is often a dense growth of annual sedges, grasses, and herbs. Submerged and floating-leaved aquatic plants, such as fragrant waterlily and pondweeds, may become "stranded" on the exposed shore. In wet years when the water level is high only a few emergents and floating-leaved aquatics may be noticeable. T

Associated Species

  • Acer rubrum
  • Cyperus
  • Juncus
  • Phragmites australis (old world reed grass, old world phragmites)
  • Typha latifolia (wide-leaved cat-tail)
  • Vaccinium corymbosum (highbush blueberry)

Range

New York State Distribution

This small herb is currently known from eastern Long island and Staten Island.

Global Distribution

This small herb has a wide distribution across the southern half of the United States from California across Oklahoma and Texas east to the Delmarva Peninsula and New Jersey. It reaches its northern limits and is considered rare in Oregon and Utah in the West, Missouri in the Midwest, as well as New York and southern New England in the East.

Identification Comments

General Description

Whorled pennywort is a low rhizomatous plant that usually occurs in masses. The leaves are round and peltate with 8-14 shallow lobes. the inflorescence is a simple spike of 1-3 whorls of tiny flowers on short peduncles with rarely more than 7 flowers in a whorl. The fruits are 3-4 millimeters wide and level or rounded at the base.

Best Life Stage for Proper Identification

The only way to identify this species is by seeing it in flower or fruit.

Similar Species

Hydrocotyle umbellata has identical leaves and it usually only has one whorl of more than 10 flowers that are on long peduncles. Sometimes it has two whorls and looks like H. verticillata but H. umbellata has more flowers, the peduncles are longer, and the base of the fruit is distinctly notched.

Best Time to See

It flowers in July through August and fruits in August through October. In August it can have flowers and fruits on the same plant.

  • Flowering
  • Fruiting

The time of year you would expect to find Whorled-pennywort flowering and fruiting in New York.

Whorled-pennywort Images


Images of Similar Species

Taxonomy

Whorled-pennywort
Hydrocotyle verticillata Thunb.

  • Kingdom Plantae
    • Phylum Anthophyta
      • Class Dicotyledoneae (Dicots)
        • Order Apiales
          • Family Araliaceae (Ginseng Family)

Additional Common Names

  • Water-pennywort

Synonyms

  • Hydrocotyle verticillata var. triradiata (A. Rich.) Fern.
  • Hydrocotyle verticillata var. fetherstoniana (Jennings) Mathias [This is an anomalous plant represented by a single collection from Livingston (not Wyoming) County, New York.]

Additional Resources

Best Identification Reference

Gleason, Henry A. and A. Cronquist. 1991. Manual of Vascular Plants of Northeastern United States and Adjacent Canada. The New York Botanical Garden, Bronx, New York. 910 pp.

Other References

Clemants, Steven and Carol Gracie. 2006. Wildflowers in the Field and Forest. A Field Guide to the Northeastern United States. Oxford University Press, New York, NY. 445 pp.

Correll, D.S., and H.B. Correll. 1972. Aquatic and wetland plants of southwestern United States. 2 volumes. Stanford Univ. Press, Stanford, California. 1777 pp.

Crow, Garrett E. and C. Barre Hellquist. 2000. Aquatic and Wetland Plants of Northeastern North America: A revised and enlarged edition of Norman C. Fassett's a Manual of Aquatic Plants. Volume One: Pteridophytes, Gymnosperms, and Angiosperms: Dicotyledons. The University of Wisconsin Press. Madison, Wisconsin. 536 Pages.

Fernald, M.L. 1950. Gray's manual of botany. 8th edition. D. Van Nostrand, New York. 1632 pp.

Godfrey, R.K., and J.W. Wooten. 1981. Aquatic and wetland plants of southeastern United States: Dicotyledons. Univ. Georgia Press, Athens. 933 pp.

Holmgren, Noel. 1998. The Illustrated Companion to Gleason and Cronquist's Manual. Illustrations of the Vascular Plants of Northeastern United States and Adjacent Canada. The New York Botanical Garden, Bronx, New York.

Mitchell, Richard S. and Gordon C. Tucker. 1997. Revised Checklist of New York State Plants. Contributions to a Flora of New York State. Checklist IV. Bulletin No. 490. New York State Museum. Albany, NY. 400 pp.

New York Natural Heritage Program. 2010. Biotics database. New York Natural Heritage Program. New York State Department of Environmental Conservation. Albany, NY.

New York Natural Heritage Program. 2023. New York Natural Heritage Program Databases. Albany, NY.

Weldy, T. and D. Werier. 2010. New York flora atlas. [S.M. Landry, K.N. Campbell, and L.D. Mabe (original application development), Florida Center for Community Design and Research http://www.fccdr.usf.edu/. University of South Florida http://www.usf.edu/]. New York Flora Association http://newyork.plantatlas.usf.edu/, Albany, New York

Links

About This Guide

This guide was authored by: Stephen M. Young

Information for this guide was last updated on: September 6, 2012

Please cite this page as:
New York Natural Heritage Program. 2023. Online Conservation Guide for Hydrocotyle verticillata. Available from: https://guides.nynhp.org/whorled-pennywort/. Accessed September 23, 2023.