What does it look like?

Phragmites karka is a perennial rhizomatous grass that can grow to heights of 4m tall in the open, or over 8m tall when supported by other vegetation. As long as there is moisture, it can establish, and can do so in any habitats including both salt and freshwater, and very dry sites like the top of sand dunes. Phragmites australis is very similar, but P.karka is a bigger plant and more aggressive.

Photo: K.Merrifield

This species spreads vegetatively from creeping rhizomes and can establish from rhizome fragments, generally establishing from fragments carried by flooding, ocean currents and tidal movements. Waterway maintenance can be a significant cause of downstream spread, via machinery or in infested soil and gravel. Phragmites karka infestations are found in a few Auckland sites, in large sites from Whangaehu River down to Scott's Ferry (Manawatū-Whanganui region) , and in smaller sites down to Paekakariki.