The first formal description of Prasophyllum plumosum was by Herman Rupp in 1942 from a specimen found near Kurnell and the description was published in The Victorian Naturalist. In 1989, David Jones and Mark Clements placed it and most other species of Prasophyllum into Genoplesium. In 2002 Jones and Clements have proposed moving all but one of Genoplesium back to Corunastylis but the move has not been widely accepted.
