Vallisneria × pseudorosulata

This taxon is a hybrid of two old world (Vallisneria denseserrulata (Makino) Makino and V. spiralis L.  The hybrid has been part of the aquatic plant trade but now has naturalized in various parts of the world including the Tennessee River drainage in Alabama.  The primary means of spreading appears to be vegetatively.

Wasekura, H., S. Horie, S. Fujii, and M. Maki. 2016. Molecular identification of alien species of Vallisneria (Hydrocharitaceae) species in Japan with a special emphasis on the commercially traded accessions and the discovery of hybrid between nonindigenous V. spiralis and native V. denseserrulata. Aquatic Botany 128: 1-6.