Vallisneria

Scientific name

Vallisneria L.

Common names

tape grass, eel grass, American wild celery

Family

Hydrocharitaceae

Native distribution

tropical and some temperate regions of the world

Species commonly cultivated

Vallisneria americana (Michx.) (and varieties) (America, Asia, Oceania, Caribbean)

V. nana R. Br. (northern Australia)

V. spiralis L. (and varieties) (Africa, Asia, Australia, Europe, Oceania)

Adventive distribution

Unclear since the distributions of V. americana and V. spiralis are very broad and species identification is difficult.

Weed status

Vallisneria spiralis is considered a serious weed in more than 50 countries on all continents. This species is troublesome by impeding water flow in irrigation canals and storage dams, blocking navigation, recreation, and agriculture.

Habit

submersed, attached rosette or stem plant

Brief description

Annual or perennial, dioecious. Stem stoloniferous, compact or elongate. Leaves typically in a basal rosette or rarely alternate along elongate stem, sessile; strap-like, linear, highly elongate to less so, width variable, sometimes twisted, venation distinctly parallel; margin serrulate. Inflorescence axillary; spathe of two united bracts subtends flower(s); male flowers small, numerous; when spathe opens flower buds liberated and open at water surface; female flower solitary, on a pedicel that elongates until flower reaches water surface and opens. Sepals 2-3, large (female flowers); 3, unequal, reflexed (male flowers); petals rudimentary or absent. Dispersal by seed and runners.

Natural habitat

still or running waters of rivers, streams, lakes, and artificial water bodies

Additional comments

The taxonomy of Vallisneria is highly problematic, resulting in numerous species being described and these names being widely distributed in the aquarium plant trade. Reliable identification of species is only possible by examining floral structures. Recent taxonomic consensus is that outside of Australia, there are two poorly defined species, V. americana and V. spiralis. Both species are now considered to contain numerous regional varieties: from the highly twisted narrow leaves of V. americana var. biwaensis (Miki) Lowden, to the very long and wide leaves (3 cm wide by >2 m long) of V. americana var. gigantea (Graebn.). Vallisneria caulescens F.M. Bailey & F. Muell. and V. triptera S.W.L. Jacobs & K.A. Frank are two closely related species from northern Australia that grow as stem plants, with leaves arranged alternately along the stems, rather than as compact, basal rosettes. Both species have recently been introduced to the aquarium trade.