Cyathea cooperi
Cyathea cooperi (W. J. Hooker ex F. Mueller) Domin [syn. Sphaeropteris cooperi (Hooker ex F. Muell.) Tryon], Australian Tree Fern, is among the most recent immigrant alien ferns, and also one of the most troublesome. Cyathea cooperi is the most commonly available tree fern in local nurseries, is a fast grower, and, unfortunately, readily escapes from cultivation. Two articles were published in 1992 that sounded the alarm about the threat posed to the Hawaiian biota by the aggressive C. cooperi. L. L. Loope et al. (1992) listed it as among "the worst alien plant invaders of Haleakala." A detailed study on the distribution, growth pattern, and impact of C. cooperi on the Hawaiian rain forests, particularly in Kipahulu Valley, Maui, was published by A. C. Medeiros et al. (1992). This study led to the recommendation that this species be formally declared a "Noxious Weed" by the state and that its distribution in the horticultural trade be halted. It was described as an invasive, disruptive species capable of radically modifying its habitat. It was reported to be escaping from cultivation from the Lyon Arboretum, Manoa Valley, O'ahu, as early as the 1950s. It is now known to be naturalized on Kaua'i, O'ahu, and Maui. On Kaua'i, in the
Koke'e area, four or five Australian Tree Ferns were planted in the 1970s, and most likely served as the source of hundreds of plants now found growing in the koa /'ohi'a forest throughout the region. Each mature plant produces large quantities of spores that are readily dispersed across long distances. It is clear that C. cooperi is an aggressive and invasive plant that seriously alters its habitat. Efforts to control it are currently limited to Haleakala National Park, while its spread continues elsewhere. New invasions are to be expected, especially as its cultivation increases.
