Spiral Ditchgrass

Ruppia spiralis Linnaeus has occasionally been used for this taxon in North America. Linnaeus, however, had never published that name ( J. T. A. Verhoeven 1979). Ruppia cirrhosa is, indeed, the correct name for the taxon (J. C. Gamerro 1968).

An implication that the North American material with long, spiraling peduncles is different from the European material of Ruppia cirrhosa stems from the statement that R. occidentalis occurs in inland lakes (J. T. A. Verhoeven 1979). No differences between European R. cirrhosa and the North American material are listed, however. In fact, a comparison of the Verhoeven's descriptive discussions for of R. cirrhosa (Verhoeven 1979) with the North American material shows that the two are the same. The genus should be studied on a worldwide basis. Until further studies indicate otherwise, I am considering North American and European material to be conspecific.

Stems to 55 cm × 0.1--0.3 mm. Leaves 3.2--45.1 cm; blade 0.2--0.5 mm wide, apex acute. Inflorescences: peduncles with 5--30 coils, 30--300 × 0.5 mm. Flowers: pistils 4--6. Fruits 1.5--2 × 1.1--1.5 mm; gynophore 2--3.5 cm; beak lateral, erect, 0.5--1 mm. 2n = 40 (Europe).

Alta., B.C., Man., N.W.T., Sask., Yukon; Alaska, Ariz., Calif., Colo., Ill., Kans., Mich., Minn., Mo., Mont., Nebr., Nev., N.Mex., N.Dak., Ohio, Okla., Oreg., S.Dak., Tex., Utah, Wash., Wyo.; West Indies; Central America; South America; Europe.

Flowering summer--fall.

Shallow to deep fresh waters of lakes with high concentrations of sulfur or calcium; 300--2500m.

Buccaferrea cirrhosa Petagna, Instit. Bot.anicae 5: 1826. 1787; Ruppia cirrhosa subsp. occidentalis (S. Watson) Á. Löve & D. Löve; R. occidentalis S. Watson

Ruppia occidentalis S. Wats. Proc. Am. Acad. 25 : 138. 1890
Ruppia lacustris Macoun, Cat. Can. PI. 5 : 372. 1890.
Stem slender, with divaricately ascending branches ; leaves all submerged and linear, 7-20 cm. long, less than 0.3 mm. wide; stipular sheaths 1.5-3 cm. long, the free part as long ; flowers similar to the preceding ; mature carpels pear-shaped, tipped by a straight style ; pedicels of the fruit less than 2.5 cm. long.
Type locality : Kamloops, British Columbia.
Distribution : From the type locality and from Nebraska.

Ruppia cirrhosa is a species of aquatic plant known by the common names spiral ditchgrass and spiral tasselweed. It is native to the Americas and Europe, where it grows in freshwater bodies, such as lakes. It is a thread-thin, grasslike perennial herb which grows from a rhizome anchored in the wet substrate. It produces a long, narrow inflorescence tipped with two tiny flowers. As the fruit develops the peduncle of the inflorescence curls into a neat spiral.