European waterstarwort: Callitriche stagnalis (Plantaginales: Plantaginaceae): Invasive Plant Atlas of the United States

European waterstarwort	USDA PLANTS Symbol: CAST U.S. Nativity: Exotic Habit: Aquatic Plants
Callitriche stagnalis Scop.

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Taxonomic Rank: Magnoliopsida: Plantaginales: Plantaginaceae
Synonym(s): pond water-starwort
Native Range: S. Europe, northern Africa, Canary Islands (BAIL);
Appearance Callitriche stagnalis is an aquatic perennial with elongate stems that can grow from 3.94-11.81 in. (1-3 dm) in length. Foliage 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 0.12-0.31 in. (3-8 mm) wide and up to 0.79 in. (2 cm) long. The submerged leaves are typically linear, have a single vein and grow 0.16-0.39 in. (4-10 mm) in length; however, they can also be broader and more closely resemble the floating leaves. Flowers 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. Fruit The fruits are nearly round (suborbicular) and 0.06-0.08 in. (1.5-2 mm) thick. Each mericarp of the fruit has a thin (0.004 in. / 0.1 mm) winged margin running from its base to its apex. Ecological Threat Callitriche stagnalis is capable of creating locally dense mats of vegetation that may crowd out native aquatic vegetation.

Selected Images from Invasive.org

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Infestation; Leslie J. Mehrhoff, University of Connecticut, Bugwood.org Additional Resolutions & Image Usage	Infestation; Leslie J. Mehrhoff, University of Connecticut, Bugwood.org Additional Resolutions & Image Usage	Infestation; Leslie J. Mehrhoff, University of Connecticut, Bugwood.org Additional Resolutions & Image Usage	Infestation; Leslie J. Mehrhoff, University of Connecticut, Bugwood.org Additional Resolutions & Image Usage
Plant(s); Leslie J. Mehrhoff, University of Connecticut, Bugwood.org Additional Resolutions & Image Usage	Plant(s); Leslie J. Mehrhoff, University of Connecticut, Bugwood.org Additional Resolutions & Image Usage	Plant(s); Leslie J. Mehrhoff, University of Connecticut, Bugwood.org Additional Resolutions & Image Usage	Plant(s); Leslie J. Mehrhoff, University of Connecticut, Bugwood.org Additional Resolutions & Image Usage
Plant(s); Leslie J. Mehrhoff, University of Connecticut, Bugwood.org Additional Resolutions & Image Usage	Plant(s); Leslie J. Mehrhoff, University of Connecticut, Bugwood.org Additional Resolutions & Image Usage	Foliage; Leslie J. Mehrhoff, University of Connecticut, Bugwood.org Additional Resolutions & Image Usage	Foliage; Leslie J. Mehrhoff, University of Connecticut, Bugwood.org Additional Resolutions & Image Usage

EDDMapS Distribution:
This map is incomplete and is based only on current site and county level reports made by experts and records obtained from USDA Plants Database. For more information, visit www.eddmaps.org

State List
This map identifies those states that list this species on their invasive species list or law.

Invasive Listing Sources:

Connecticut Invasive Plant Working Group

Native Plant Society of Oregon, 2008

WeedUS - Database of Plants Invading Natural Areas in the United States