Stem: Many branched stems, to 0.5 m long, less than 1 mm wide, root at the nodes and often have a zig-zag appearance. Produces slender horizontal rhizomes.

Flower: Tiny flowers (3-5 mm across), lack petals and sepals, and occur in pairs on stalks. Pollination often occurs underwater or at the waters surface. Once pollinated, the flower stalk coils.

Fruit: Dark colored, egg to pear-shaped, symmetrical to highly asymmetrical achene is 1.5 to 2 mm long and occurs in a cluster. Each fruit is on individual stalks, but all are connected to a long flowering stalk (peduncle). R. maritima: peduncle 0.2-2 cm, less than 3 coils. R. cirrhosa: peduncle 3-30 cm, more than 5 coils.

Root: Fibrous. From lower nodes of erect stems and shallowly buried rhizomes.

Propagation: Seeds, fragments, rhizomes; occasionally produces overwintering buds. 

Importance of plant: Provides cover and food for many aquatic species. All the plant parts are eaten by waterfowl (over 5,000 seeds were found in one duck). Often used for habitat rehabilitation.

Distribution: Worldwide.

Habitat: Ruppia maritima: mostly a coastal species found in brackish water and will tolerate tidal exposure. Ruppia cirrhosa: mostly an inland plant found in alkaline lakes.

May be confused with: Each other. Penducle length is the most consistently different physical characteristic; habitat also helps. R. maritima is usually in coastal salty water, and R. cirrhosa is usually in inland alkaline water. When not in flower or fruit, they closely resemble sago pondweed (Potamogeton pectinatus), but sago pondweed has stipules that are not completely fused to the leaf. 

Photographs: Closeup of Ruppia maritima 

Line Drawings: Ruppia