The Flowering Plants of Hawaii
Part 11 Casuarinaceae - Cecropiaceae
Casuarinaceae, a small family with only four genera and 95 species, are native to Australia and the western Pacific. Casuarina, the genus of interest to us here, consists of 17 species. The most frequently seen species is C. equisetifolia, known commonly by a variety of names including Australian pine (no relation to Pinus, but it’s a convenient name), common ironwood, she-oak, beefwood, or simply as casuarina. Its characteristic flowers and cones are seen in the photo. It has been widely planted as a windbreak—in the Hawaiian Islands and throughout the Pacific basin—as well as for its usefulness as a timber tree.
This species is widespread in the Hawaiian Islands occurring on all of the main islands and on many of the northwestern islands. A casuarina forest, showing the tendency to overwhelm all other vegetation, can easily be visited on Moloka`i’s northern coast at the overlook to the Kalaupapa Peninsula (see image). Folks who stroll barefoot on beaches will likely have encountered the cones of this species! Extensive plantings of casuarina, heavily clipped by the Trade Winds, can be seen from the road along the eastern cliffs of Moloka`i (see image). The very similar Casuarina glauca has also been extensively planted in the islands. A view of this species lining one of the tracks on Läna`i is seen in the photo.
In spite of the usefulness of casuarina as a valuable timber tree and as a beach stabilizer, there is more to the story. In short, casuarina is one of the most aggressive alien trees on the Hawaiian Islands. It grows rapidly, produces heavy seed crops, and prevents colonization of other species—natives and other aliens alike—through the massive amount of leaf litter that accumulates. One writer, Maui Mike (Michael T. Garrison), has called it “The pine tree’s evil twin.” See also Floridata's Casuarina equisetifolia profile.
Historically, this family of six genera and about 300 species (Manual) was considered to be intermediate between Moraceae (fig family) and Urticaceae (nettles) but is now considered part of the latter (Soltis et al., p. 176). Future treatments of the Hawaiian flora will undoubtedly recognize this new alignment. Cecropia is a genus of 61 species from tropical America (Mabberley, p. 162). A single naturalized species occurs on the Hawaiian Islands, Cecropia obtusifolia (see image), known commonly as the trumpet tree. This species occurs naturally from southern Mexico to Ecuador. In the islands it occurs in open fields and wet forests on Kaua`i, O`ahu and on the Big Island. Particularly healthy populations of trumpet trees can be found along the southeastern coast road on the Big Island.
January 13, 2011