Submersed Plants

 
Species: Callitriche heterophylla Pursh., different-leaved water-starwort
Callitriche verna L., spring water-starwort
Family: Callitrichaceae

Water-starworts are small, delicate plants usually found in shallow water. All species present in the Northwest are loosely rooted to the bottom, and have narrow underwater leaves and/or broadened floating leaves arranged in pairs along thin stems. Characteristics of water-starworts are quite variable and depend on growing conditions. To be sure of their identification to species, the surfaces of mature fruits need to be examined under 10-20x magnification. Different-leaved and spring water-starwort have narrow underwater leaves, and both can have spoon-shaped floating leaves that form rosettes on the water surface.

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Leaf: Opposite. 2 types: submersed and floating leaves. Different-leaved: narrow submersed leaves are 0.5-2.5 cm long with two rounded leaf tip lobes; oval floating leaves (to 1 cm wide) are sometimes present and form rosettes on the water surface; leaf bases are joined by a wing-like ridge. Spring: narrow, pale-green, submersed leaves are 0.5-2 cm long and to 1 mm wide with a slight indentation at the tip; spoon-shaped floating, emergent, or terrestrial leaves are sometimes present, up to 4 mm wide, one rounded tip per leaf, with the leaf bases joined by a wing-like ridge.

Stem: The thread-like branched vertical-to-trailing stem is usually less than 50 cm long.

Flower: Small flowers are located at the leaf bases. They lack sepals or petals, instead 2 small whitish bracts serve as "petals."

Fruit: Four tiny, nut-like fruits per flower; each containing one seed. Different-leaved: heart-shaped, with no narrow margin, 0.6-1.4 mm across. Spring: narrow margin all around, tiny pits create vertical lines on surface, 0.9-1.4 mm long, 0.8-1.3 mm wide, generally wider above middle.

Root: Fibrous, from base of the plant and loosely anchoring plants to the bottom.

Propagation: Plant fragments and seeds.

Importance of plant: Provides forage and habitat for aquatic insects and fish. Ducks eat foliage and seeds.

Distribution:  Different-leaved: North and South America. Spring: Northern Hemisphere.

Habitat: Lake margins and slow streams. May carpet the mud when water levels drop.

May be confused with: Other water-starworts. Not all water-starworts occurring in the Northwest are included in this book. Refer to technical keys for additional descriptions. Also, floating leaves may at first resemble duckweeds (Lemna minor and Spirodela polyrhiza) which are both free-floating. When not in fruit they can be confused with other delicate opposite-leaved shoreline plants like mudwort (Elatine sp).

Photographs: Callitriche verna mat

Line Drawings: Callitriche heterophylla


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