The New Zealand native grasslands are dominated by species with the tussock or “bunch grass” habit. These have much mechanical tissue and do not die back to the ground in winter. Tussock grasslands are found from sea level to the alpine zone and fall into two broad categories. Low-tussock grassland is dominated by species of Festuca and Poa, a half-metre or more in height and yellow-brown in general appearance, and belongs to lower, drier areas. Talltussock grassland is dominated by one or another of the snow grasses (Chionochloa spp.), which are usually a metre or more high and yellow, green-brown, or red-brown in appearance. They are generally found today at higher altitudes and in wetter conditions.
Low-tussock grassland: About a century ago this community covered considerable areas of eastern South Island from sea level to 800–900 m and in many places invaded areas where beech forest had been cleared. Large areas of induced low-tussock grassland occur also to the east of the central plateau of the North Island.
A detailed study by Barker (1953) on Hunters Hills, South Canterbury, listed the dominants in low-tussock areas as Festuca novae-zelandiae (hard tussock), Poa caespitosa (silver tussock), and Poa colensoi (blue tussock). Hard tussock is the most abundant, it is deep rooted, and dominant on steep, exposed slopes. Silver tussock is shallow rooted, grows in more mesophytic conditions, and, unlike the other two, does not occur in tall-tussock grassland. The blue tussock grows with the other species and may be dominant locally on shallow soils. The spiny shrub Discaria toumatou (wild Irishman) and the Aciphyllas (spear grasses) are also common on low-tussock areas.
Tall-tussock grassland: Tall tussock communities are found on Mount Egmont and from there southward throughout the high country of both Islands, sometimes above forest. At lower levels tall tussock may be found on coastal hills, as on Banks Peninsula, or on the Southland Plain.
Chionochloa rubra (red tussock) dominates large areas in central North Island devastated by volcanic eruptions. In the South Island it is common on poorly drained terraces and abundant particularly in Southland. C. pallens and C. flavescens are important in the North Island mountain chain, and with C. rigida dominate in the South Island. C. crassiuscula is common in South Island mountains, and with C. pungens forms the meagre high-altitude grassland found on Stewart Island. In northern South Island C. australis, a lax species with smooth leaves, forms a slippery “carpet” grassland. The dominant species in the Hunters Hills tall tussock are C. rigida and the cotton plant, Celmisia spectabilis, with Festuca novae-zelandiae and Poa colensoi. The cotton plant has tufts of stout linear-oblong leaves with dense tomentum beneath, and a well protected growing point enabling it to survive forest fires. In inland North Otago a snow-tussock community of Chionochloa rigida, with Festuca matthewsii common, was described by Connor (1961).
The original tussock grassland evolved in the absence of grazing animals, and has been modified in greater or lesser degree during a century of stocking. In drier areas, such as Central Otago and inland Marlborough, the results have been serious. Here burning and stocking opened up the grassland, making an ideal home for rabbits. Their depredations accelerated vegetation changes which included spectacular increase of scab weed (Raoulia australis), a composite mat plant. Legislation has been introduced to control both burning and rabbits.