Kingdom:   Plantae
(Unranked):    Angiosperms
(Unranked):    Monocots
(Unranked):    Commelinids
Order:     Poales
Family:    Cyperaceae (sedges)
Genus:        Gahnia
Species: G. xanthocarpa
Binomial name: Gahnia xanthocarpa
Synonyms: Lampocarya xanthocarpa, Gahnia ebenocarpa, Claudium xanthocarpum, Gahnia setifolia (A. Rich.) Hook. f. var. xanthocarpa
Common names: Giant cutty grass, Mapere, Gahnia. 

Gahnia xanthocarpa is large robust perennial sedge endemic to the North Island from Te Paki south to Wellington including Mt Egmont/Taranaki. In the South Island, it is found from Nelson, Marlborough, Westland and Canterbury.
It grows in from the coast up to 800 m plus and seems to prefer permanently damp situations within alluvial forests, swamp forest and the margins of lowland swamps, bogs and waterways. 
Gahnia xanthocarpa forms large stout tussocks up to 2m across and 3 m tall. The leaves have very harsh sharp cutting edges and are approximately 1 cm wide. The much branched drooping flower spikes that are over 3m and 1.5+ cm wide appear January - April with red/pink flowers. The 5 x 2 mm fruits which are glossy black nuts when ripe may be found throughout the year. Used for revegetation work in environmental plantings. 

For more details visit http://www.nzpcn.org.nz/flora_details.asp? ID=1908 

Photographed at Otari NativeBotanic Garden and Wilton's Bush Reserve. Wellington.
Gahnia xanthocarpa-001.JPG 

Gahnia xanthocarpa-002.JPG 


Thanks to Wikipedia for text and information: https://creativecommons.org/licenses/by-sa/3.0