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Aquatic and Wetland Vascular Plants of the Northern Great Plains

56. Ruppiaceae, The Ditch-grass Family

1. Ruppia L. -- Ditch-grass, widgeon-grass

1. Ruppia maritima L.


Perennial submersed aquatic; stems slender and terete, flexuous, anchored by roots, branching at the base and short-branched above, to 6 dm long, the internodes often zigzag. Leaves simple, alternate, sessile, the blades filiform, attenuate, mostly 5-15(25) cm long, ca. 0.5 mm wide, stipular-sheathing at the base. Inflorescence a reduced axillary spike, included in the leaf sheath at anthesis; peduncles elongating and usually coiling as fruits develop. Flowers 2 per spike, perfect; perianth none or minute; stamens 2, briefly adherent during peduncle elongation; carpels 6 or more, separate, stipitate, the stipes gradually elongating from the common base so that the fruits are borne in an umbel. Fruits olive-green to black, ovoid, symmetrical to asymmetrical, beaked, 1.5-3 mm long. Jul--Aug. Alkaline to saline waters of lakes, ponds and marshes; locally common and scattered throughout the region; (Coastal marshes from N.Amer. to S.Amer. and in the Old World, also inland throughout Can. and the U.S., primarily in brackish or saline waters).

Two fairly distinct forms can be recognized in the region. The prevalent form is var. occidentalis (Wats.) Graebn., a robust, strongly rhizomatous plant with leaf sheaths 1.5-3 cm long. This variety often forms extensive grasslike mats in alkaline waters. A smaller form of lesser occurrence most closely fits var. rostrata Agardh., with leaf sheaths to 1 cm long. This form seems to favor waters of more extreme salinity.
GIF- Species Photo/Drawing
Ruppia maritima
GIF- Distribution Map

Map key


Return to Family -- Ruppiaceae - The Ditch-grass Family

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