ALIEN FERNS IN HAWAI'I

Blechnum appendiculatum Willd., Hammock Fern, a garden escape from tropical America, has continued its spread throughout Hawaiian forests since Wagner reported it in 1950. It is now a very common weedy fern along trail sides, stream banks, forested slopes, and gulches on all islands, often growing in solid stands. In 1917 C. N. Forbes collected B. appendiculatum in the Honokohau Drainage Basin on Maui, remarking in his notes that the genus was new to the Islands. Soon afterwards it was collected on O'ahu and Kaua'i. Degener (1946a) pointed out that "this fern is spreading rapidly along dry, partly shaded embankments". Warren H. Wagner (1950) remarked that in the middle and late 1940s it was "common in suitable places everywhere" on all of the islands except Hawai'i. This aggressive, fast-growing fern is now widely naturalized in Hawai'i, often in large populations, effectively preventing the germination and growth of native species where it occurs. Smith (1985) listed B. occidentale as a candidate for monitoring because of its potential for becoming a serious pest. There has been no improvement of the situation since. Long incorrectly referred to as Blechnum occidentale L., it is properly known as Blechnum appendiculatum which differs in having rachises that are pubscent and glandular on the abaxial surface.