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Statistics on New Zealand’s grasses

Grasses are the second largest plant family in New Zealand with 464 species (190 indigenous species and 274 naturalised species (Edgar & Connor 2010) making up 11% of seed plants in New Zealand (indigenous & naturalised). Endemism is high with 84% of species found nowhere else. The grasses have the largest number of naturalised species of any plant family, exceeding the number indigenous grass species by 12%, and making up 7% of all seed plants in New  Zealand. Grasslands and mosaics of grass and scrub cover nearly 60% of New Zealand (Wardle 1991).

Most indigenous grasses are concentrated in three tribes – the Agrostideae (Agrostis, Lachnagrostis, Deschampsia, Deyeuxia, Koeleria, Trisetum), Danthonieae (Chionochloa, Rytidosperma), and the Poeae (Festuca, Poa). The panicoids are poorly represented with just three indigenous species, and bamboos are absent altogether.

Naturalised species are concentrated in the Agrostideae (Agrostis, Anthoxanthum, Avena, Phalaris), Hordeeae (Critesion), Paniceae (Panicum, Paspalum, Pennisetum, Setaria) and the Poeae (Festuca, Poa). About 40% of naturalised species are from Europe and 15% are from Australia. Most of the European species belong to the genera Avena, Critesion, Poa or Festuca. Nearly all the naturalised Australian species are from the stipoid genus Austrostipa or the danthoid genus Rytidosperma. Another stipoid genus present here is Nassella from South  America, represented by three weedy species, including the well-known invasive ‘nassella tussock’ (Nassella trichotoma).