Herbarium specimen MNHNL22119 at the Luxembourg National Museum of Natural History.

Ceratophyllum submersum L., commonly known as the soft hornwort, is a submerged, free-floating aquatic plant.

A very dense submerged population of the soft hornwort was discovered in a pond near Sanem on 21st June 2015 by German botanists Jörg Zoldan and Annette Steinbach-Zoldan during a survey for the nature conservation organisation SICONA-Ouest. The pond had been artificially created in 2010.

In November 2015 specimens from this population were deposited in the herbarium of the Luxembourg National Museum of Natural History.¹

Ceratophyllum submersum, Flora Batava Vol. 19, 1893. Wikimedia Commons.