COMMON NAME

European frogbit


FULL SCIENTIFIC NAME

Hydrocharis morsus-ranae L.


FAMILY NAME COMMON

Frog's Bit family


FAMILY SCIENTIFIC NAME

Hydrocharis morsus-ranae


IMAGES


Flower

Habit/Habitat

NOMENCLATURE/SYNONYMS

Synonyms: None


DESCRIPTION

Botanical Glossary

Hydrocharis morsus-ranae is an herbaceous, annual aquatic that can reach 20 cm (8 in.) in length. The plant is free-floating (unattached to the bottom substrate of the water body). The leaves of this plant are usually floating, but if the vegetation is dense enough, they can be emergent. The leathery, glabrous leaves are cordate-orbicular in shape and measure 1.2-6 cm (0.5-2.25 in.) in length and (0.5-2.5 in.) in width. The lower leaf surfaces are often dark purple in color. The lateral veins of the leaves are broadly arching, making a 75 to 90 degree angle in relation to the midvein. Hydrocharis morsus-ranae is a dioecious plant. One to five staminate flowers are contained in spathes borne on peduncles that measure 4 cm (1.5 in.) long. There is only one pistilate flower on each plant. The 3-petaled pistilate flowers are white in color with a yellow spot in the center. These flowers measure 1 cm (0.4 in.) across. The pedicels of the pistilate flowers measure 9 cm (3.5 in.) long. The seeds of Hydrocharis morsus-ranae are around 1 mm (0.04 in.) in size. This plant can also produce stolons, which allow it to reproduce asexually. It is able to form large colonies that appear as dense floating mats of vegetation. Page References Bailey 132, Crow & Hellquist 28, Flora of North America 21, Gleason & Cronquist 638, Holmgren 606. See reference section below for full citations.


SIMILAR SPECIES

Limnobium spongia (Bosc) Richard ex Steudel (American frogbit)


REPRODUCTIVE/DISPERSAL MECHANISMS

Hydrocharis morsus-ranae spreads rapidly by way of long, cord-like stolons, easily giving rise to a floating mat of interconnected plants. It is capable of over-wintering by forming vegetative buds, called turions, located at the base of the plant. Hydrocharis morsus-ranae is also capable of sexual reproduction, but seed production is often limited and sometimes non-existent.


DISTRIBUTION

Hydrocharis morsus-ranae is native to Europe. In North America it has spread from original sites in Ottawa, Canada to Quebec, the St. Lawrence River, Lake Erie and Lake Ontario. In the U.S. it is currently found at limited sites in the states of New York, Vermont, Michigan and Washington.


HISTORY OF INTRODUCTION IN NEW ENGLAND

Several plants from Zurich, Switzerland were placed in ponds near the Central Experimental Farm Arboretum of Ottawa in 1932. These apparently escaped and spread from the Ottawa region to the St. Lawrence River by the 1960s. In 1993, Hydrocharis morsus-ranae was found in Lake Champlain. By 1999 it was found south of Lake Champlain in several Vermont sites (Benson, Orwell and West Haven).


HABITATS IN NEW ENGLAND

Aquatic, Lake or Pond, River or Stream

Hydrocharis morsus-ranae grows well in quiet open water. It can be found in marshes, ditches and swamps. It grows well in sheltered coves and along the still water shorelines of rivers, lakes and streams.


THREATS

Hydrocharis morsus-ranae has rapid vegetative spread and the ability to form dense mats, which can limit light penetration and fill the water column in shallow areas. In doing so it can strongly affect native aquatic life. It can also inhibit boat traffic and limit recreational activities.


DOCUMENTATION NEEDS

Documentation required: Herbarium specimen or mounted snippet of the plant with flowers.
Best time for documentation: Summer, fall.


ADDITIONAL INFORMATION

Integrated Taxonomic Information System
Taxonomic information about the species

USDA Plants database
General information and map

Flora of North America
Extensive description

USGS Nonindigenous Aquatic Species
U.S. distribution information

University of Florida, Center for Aquatic and Invasive Plants
Images


REFERENCES

Bailey, L.H.  1949.  Manual of Cultivated Plants.  Macmillan, New York.

Catling, P.M., Z.S. Porebski. 1995. The spread and current distribution of european frogbit, Hydrocharis morsus-ranae L., in North America. Canadian Field Naturalist 109 (2): 236-241.

Crow G.E. and C.B. Hellquist. 2000. Aquatic and Wetland Plants of Northeastern North America. Vol #2. University of Wisconsin Press, Madison.

Flora of North America Editorial Committee, eds. 1993+. Flora of North America North of Mexico. Volume 1. Oxford University Press. 

Flora of North America Association ed. 2000.  Flora of North America vol. 22. Oxford University Press, 
Oxford, New York.

Gleason H.A. and A.C. Cronquist.  1991.  Manual of Vascular Plants of the Northeastern United States and Adjacent Canada. 2nd ed.  New York Botanical Garden, Bronx, New York.

Holmgren N.H. 1998. Illustrated Companion to Gleason and Cronquists Manual.  New York Botanical Garden, Bronx, New York.

USDA, NRCS.  2001.  The PLANTS Database, Version 3.1. (http://plants.usda.gov).  National Plant Data Center, Baton Rouge, LA 70874-4490 USA.