COMMON NAME

Pond water-starwort

FULL SCIENTIFIC NAME

Callitriche stagnalis Scop.

FAMILY NAME COMMON

Water-starwort family

FAMILY SCIENTIFIC NAME

Callitriche stagnalis

IMAGES

Submerged form	Habit	Incursion
Habit close-up	Leaves close-up

NOMENCLATURE/SYNONYMS

Synonyms: None

DESCRIPTION

Botanical Glossary

Callitriche stagnalis is an aquatic perennial with elongate stems that can grow from 1 to 3 dm (3.94 to 11.81 in.) in length. Its leaves are opposite, entire and somewhat diverse in form, depending on whether they are submerged or floating. The floating leaves are spatulate-obovate in shape, have 5 to 7 veins, are 3-8 mm (0.12 to 0.31 in.) wide and up to 2 cm (0.79 in.) long. The submerged leaves are typically linear, have a single vein and grow 4-10 mm (0.16 to 0.39 in.) in length; however, they can also be broader and more closely resemble the floating leaves. Callitriche stagnalis is monoecious. The staminate and pistillate flowers are tiny, simple in structure and typically located right next to one another in the leaf axils. This close proximity facilitates aerial self-pollination. The flowers have two small bracts at their bases, which may help the flowers to float on the water, also facilitating pollination. The fruits are nearly round (suborbicular) and 1.5-2 mm (0.06-0.08 in.) thick. Each mericarp of the fruit has a thin (0.1 mm / 0.004 in.) winged margin running from its base to its apex. The flowering period in New England is from August to December. Page References Crow & Hellquist 315, Fernald 973, Gleason & Cronquist 459, Holmgren 431, Magee & Ahles 706. See reference section below for full citations.

SIMILAR SPECIES

Callitriche spp. Callitriche stagnalis is most easily distinguished from the other Callitriche spp. in North America by its nearly round (suborbicular) fruit and the marginal wing that extends around each mericarp from its base to its apex. It is very difficult to tell the different species of Callitriche apart when they are not in fruit.

REPRODUCTIVE/DISPERSAL MECHANISMS

Callitriche stagnalis reproduces by clonal spread and by prolific seed production. However, there are exceptions to this rule of prolific seed production: in Danbury, CT there is a large population of C. stagnalis that seldom if ever produces seed (Thomas Philbrick, 2003 - pers. comm.). Clonal reproduction allows this plant to form locally dense mats of vegetation. It does not have specialized vegetative propagules, but it does seem capable of dispersing by way of plant fragments. The extent of its dispersal by plant fragmentation is not known. Seeds probably constitute its major mode of dispersal. Callitriche stagnalis appears to be capable of self pollination, which generally facilitates greater seed production. Bird dispersal, either by seed ingestion or by attachment of seeds or fragments to feathers, is also possible. Vehicular dispersal, caused when mud with seeds in it gets stuck to boats and tires, may also be important.

DISTRIBUTION

Callitriche stagnalis is native to both Europe and North Africa, where it is widespread in aquatic and subaquatic habitats. It has a somewhat scattered distribution in North America. In Canada it is found in the St. Lawrence seaway, Newfoundland (its northern most location) and British Columbia. In the U.S., Callitriche stagnalis is found in all of the mid Atlantic states, Virginia, Tennessee, Alabama, Wisconsin, Montana and along the West coast. In New England it has been reported in Massachusetts and Connecticut.

HISTORY OF INTRODUCTION IN NEW ENGLAND

The earliest record of Callitriche stagnalis in North America comes from New York in 1861. The exact mechanism of its introduction is unclear; however, it initially became established near seaports, suggesting that it may have been accidentally released through shipping. Callitriche stagnalis became a popular aquarium plant before the end of the nineteenth century. This may help to explain some of its subsequent non-coastal populations (for example in Montana, first specimen in 1898), since it is likely that aquarium disposal contributed to its accidental dispersal. The earliest record of Callitriche stagnalis in New England comes from Cape Cod (Barnstable county, Massachusetts) in 1911. In general, the number of herbarium specimens for Callitriche stagnalis has shown a gradual increase over the last century, indicating that it may have spread more slowly than some other notable invasive aquatic plants, or it has been somewhat overlooked by collectors.

HABITATS IN NEW ENGLAND

Callitriche stagnalis is found in non-moving to slowly moving water, mostly in ponds, marshes and along the protected banks of streams and lakes.

THREATS

Callitriche stagnalis is capable of creating locally dense mats of vegetation that may crowd out native aquatic vegetation.

MANAGEMENT LINKS

DOCUMENTATION NEEDS

Documentation required: Herbarium specimen or mounted snippet of the plant in fruit.
Best time for documentation: Late summer, fall.

ADDITIONAL INFORMATION

Integrated Taxonomic Information System
Taxonomic information about the species

The PLANTS Database
General information and map

Washington State Department of Ecology
Description

University of Wisconsin Herbarium

University of Washington Herbarium

Crow, G.E. and C.B. Hellquist. 2000. Aquatic and Wetland Plants of Northeastern North America. Vol #1. University of Wisconsin Press, Madison.

Fernald, M.L. 1950. Gray's Manual of Botany 8th ed. American Book Co., Boston.

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.

Holm, L.G., J.V. Pancho, J.P. Herberger and D.L. Plucknett. 1979. A Geographical Atlas of World Weeds. John Wiley and Sons, New York, USA.

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

Les, D. and L. Mehrhoff. 1999.  Introduction of nonindigenous aquatic vascular plants in southern New England : a historical perspective.  Biological Invasions  1: 281-300.

Magee, D.W and H.E. Ahles. 1999.  Flora of the Northeast. University of Massachusetts Press, Amherst.

Philbrick, C.T., R.A. Aakjar and R.L. Stuckey. 1998. Invasion and spread of Callitriche stagnalis in North America.  Rhodora 100: 25-38.

Philbrick, C.T. and G.J. Anderson. 1992.  Pollination biology in the Callitrichaceae.  Systematic Botany  17: 282-292.

Philbrick, C.T. 1989.  Systematic studies in North American Callitrichaceae.  Ph.D. dissertation, University of Connecticut.  Storrs, Connecticut.

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