ECOLOGY AND DISTRIBUTION OF NATURALIZED SPECIES OF STIPA IN NEW-ZEALAND

Nine species of Stipa are naturalised in New Zealand, eight of them from Australia. Another Australian species, S. nitida, was found in Marlborough in the 1940s but has not been seen since. The widespread species S. nodosa and S. scabra are short tussock-forming plants with falcate awns and are found in eastern South Island from Marlborough to Otago; their period of expansion was the late 19th Century. Five tall, stout, Australian species with bigeniculate awns are of localised distribution and would seem not to have expanded very greatly since their arrival in New Zealand. The only species of South American origin naturalised here, S. neesiana, has proved troublesome in Marlborough and to a lesser extent in Hawkes Bay. This species has the most versatile reproductive system of any species of Stipa in. New Zealand. It produces cleistogenes, clandestine panicles at culm nodes, as well as an apical inflorescence. Whether or not these characters have aided its modest success is unknown. Despite features of the seeds which would aid dispersal, only the falcate Australian species have attained wide distribution. The weed potentiality of Stipa spp. is slight.