Asia (India, China, Vietnam)
Species commonly cultivated
Nechamandra alternifolia (Roxb.) Thwaites (Asia)
established in Sudan and Sri Lanka
not known to be a serious weed; declared as a prohibited, noxious weed in Florida (United States)
Annual or perennial. Stem greatly elongated, irregularly branched. Leaves alternate, cauline, sheathed at base; leaf blade elongate, veins parallel, without prominent midrib; margins minutely serrated. Flowers unisexual, axillary; female flowers borne on elongate pedicel-like stalks (actually hypanthia) and opening at water surface; male flowers minute, numerous, abscising from small spathe and opening while floating freely on water surface; sepals 3; petals absent or rudimentary.
typically found in still, temporary waters
This genus was originally thought to be closely related to worldwide environmental weed Lagarosiphon, but was subsequently considered to be very closely related to Vallisneria based on floral characteristics. Nechamandra is considered a serious potential environmental weed and is declared as a prohibited noxious weed by state authorities in Florida (United States), yet no basis for that conclusion can be found. Nechamandra alternifolia is very similar in appearance to Vallisneria caulescens Bailey & Muell. and V. triptera Jacobs & Frank from northern Australia. This genus is not presently known to be cultivated for aquaria or ponds, but has potential for the future.