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Ironwood, Australian pine

Invasive weeds in Hawaii

This page contains information about ironwoods (Casuarina spp.) as invasive weeds in Hawaii, including links to some of the best Casuarina sites on the web. If you know of other sites to which there should be a link from this page, please e-mail the HEAR webmaster at

Information about Casuarina spp. as invasive species in Hawaii

Casuarina species (known commonly as ironwood or Australian pines) are highly invasive, extremely problematic weeds in Hawaii. This species should not be planted anywhere in the state of Hawaii (even though it is already established in some areas), because the damage that it causes (e.g. to native ecosystems) is permanent and irreversible. It is impossible to have "just a few" of these plants: . Planting "just one" has effects outside the area where it's planted; it's not just the immediate vicinity that can be permanently negatively affected. Nor is it the immediate future that is the only consideration; a planting of a reproducing, wide-spreading (via birds, wind, etc.) species can potentially last forever, affecting areas both near and far over time.

In a report on the status and ecology of the endemic and Federally-listed endangered 'awiwi* (Centaurium sebaeoides [Gentianaceae]), Medeiros et al. (b) state, "Threats to Centaurium sebaeoides at the eleven study populations include 1) displacement by non-native woody species.... Non-native woody species capable of invading and highly modifying C. sebaeoides habitat include Casuarina equisetifolia, C. glauca.... Site invasion by Casuarina appears to be particularly damaging due to the smothering leaf litter layers which exclude most plant species" [emphasis added].

In a report regarding botanical resources and threats to them in Ka'uhako Crater (Kalaupapa National Historical Park, Moloka'i), Medeiros et al. (a) quote Linney (1987) with respect to Casuarina equisetifolia in the crater, "little grows between the trees, where the shade is quite deep, and a layer of 'needles' covers the ground to a depth of a decimeter or more. There is no real understory." They state further, "Based on observations and data recorded in cover plots immediately below the ironwood stand, this litter comprises a significant portion of the ground cover and obviously plays an important role in the suppression of seedling recruitement in the understory. In effect, ironwood is displacing the upper margins of the 'Ohe makai-Hala pepe forest" [emphasis added]. (This forest is later described as containing "the finest example of native vegetation in the immediate area.") (Ka'uhako Crater is a site very rich in Hawaiian culture, as well; cultural resources in this area may also be at risk by invasion of Casuarina and/or other invasive alien species.)

These are only two examples of a multitude of problems caused by Casuarina species (ironwood) in Hawaii. Please do not plant ironwood in Hawaii!

Species that are problematic in other areas are extremely likely to be problematic in areas with similar climates; therefore any species that are problematic in south Florida, for example, will likely create the same problems in Hawaii. In the case of Casuarina species, Hawaii has already experienced similar problems as those in south Florida. The examples below from south Florida or other areas are indicative of the types of problems that Hawaii experiences and will experience with respect to Casuarina species.

*The proper spelling of the Hawaiian word "'awiwi" includes a macron over the initial "a"; this was intentionally omitted for purposes of indexing/searching and display on the web. The correct spelling should always be used in hardcopy documents, and if the word is used in other web-based documents, this explanation should be included.

Links to external Casuarina sites

(Note: Eventually, the format of this page will change to include the title and a brief description of each linked page. It's posted now "as is" just to get the info out, albeit in a less-than-most-useful format. If you wish to volunteer to assist with reformatting this page, please contact the HEAR webmaster at

References cited

Other references

Pinyopusarerk, K., and House, A.P.N. (1993). 'Casuarina: An Annotated Bibliography of C. equisetifolia, C. junghuhniana and C. oligodon'. (International Centre for Research in Agroforestry: Nairobi). 298 pp.

U.S. Congress, Office of Technology Assessment, Harmful Non-Indigenous Species in the United States, OTA-F-565 [Washington, DC: U.S. Government Printing Office, September 1993].

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This page was created on 17 November 1999 by PT, and was last updated on 17 November 1999 by PT. The HEAR website is indexed on AltaVista.