From: David H. Lorence <lorence@aloha.net>

Subject: Alien plants

Tuesday, December 02, 1997 10:37 AM

Regarding alien species which have the potential of becoming bad weeds on Pohnpei (and on tropical high islands in general)

Tim Flynn and I just finished updating our checklist of Pohnpei vascular plants just last week, incorporating observations and collections from our Sept. trip. We came up with a short list of some species alreadly seen growing on Pohnpei which have proven to be particularly bad weeds in Hawaii and elsewhere. Here they are:

• Acacia auriculiformis Cunn. ex Benth. (Fabaceae). The government seems to be encouraging the cultivation of this acacia, but it is already becoming naturalized and has the potential of spreading and becoming an unwelcome weed. Discourage people from planting it.
  http://www.horticopia.com/plantlist/pl37.htm
  http://www.hort.purdue.edu/newcrop/duke_energy/Acacia_auriculiformis.html
• Coccinea grandis (L.) Voigt (Cucurbitaceae) "Ivy gourd" This is smothering, fast-growing vine with red, bird-dispersed fruits. We observed fit least 1 plant in cultivation at the Pohnpei Agriculture Station in Kolonia, growing on a trellis by the nursery. People sometimes eat the shoots as greens [in Hawaii and SE Asia], and presumably this is why it was planted at the station. We told Kadalino Lorenz that it could become a very carious problem and that he should get rid of the plant as soon as possible. But you really should check to see if any action was taken. The plant(s) at the Agriculture station (Botanic Garden) must be eliminated before it spreads! Cut the stems near ground level and apply an herbicide such as concentrated Roundup or Garion. It has become a very serious weed on Oahu and the Big Island--virtually uncontrollable now. About an acre of it was recently found on Kauai, and life weed control people attacked it immediately. This species is dioecious.
• Melaleuca quinquenervia (Cav.) S.T. Blake (Myrtaceae) "Paper bark tree" native of Australia, this has become very weedy in Hawaii. In the Florida Everglades it has become a scourge of the wetlands and costs millions of dollars to control. Get rid of it before it becomes more widespread in Pohnpei.
  http://www.nbii.gov/invasive/Melaleuca/Melaleuca.html
  http://www.nps.gov/plants/alien/fact/mequ1.htm h
  ttp://www.floridaplants.com/Eflora/melaleuca_quinquenervia.htm
• Psidium cattleianum Sabine (Myrtaceae) "Strawberry guava", with red and yellow-fruited forms. This is one of the most serious pests in Hawaii. We have seen the yellow-fruited form [P. c. forma lucidum Degener] in cultivation on Pohnpei. Birds and pigs disperse the fruits of this small tree, which forms dense thickets, especially in valley bottoms and moist or wet slopes. Is known to be allelopathic, inhibiting the germination and growth of other species.
  http://www.nps.gov/plants/alien/fact/psca1.htm
  http://newcrop.hort.purdue.edu/newcrop/morton/cattley_guava.html
  http://tncweeds.ucdavis.edu/esadocs/psidcatt.html
  http://www.botany.hawaii.edu/cpsu/strawgua/strawgua.html
• Scheffiera actinophylia (Endi.) Harms (Araliaceae) [(Brassaia actinophylla)]"Octopus tree" from Queensland. This tree has bird-dispersed fleshy fruits and has become extremely invasive on windward Kauai and other islands, in moist to wet areas. We noticed it in cultivation in Kolonia; people should be discouraged from growing it.
  http://farrer.riv.csu.edu.au/ASGAP/jpg/960816.jpg
  http://edis.ifas.ufl.edu/scripts/htmlgen.exe?DOCUMENT_4H001
  http://farrer.riv.csu.edu.au/ASGAP/s-actin.html
  http://www.ext.msstate.edu/anr/plantsoil/homehort/mg/schef.html
  http://www.macore.com/gu/01321939.htm
  http://www.planetpets.simplenet.com/hsesheff.htm
• Spathodea campanulata Beauv. (Bignoniaceae) "African tulip tree", has become weedy in the moist and wet areas of Hawaii. Wind-dispersed seeds help it spread readily.

Here are several more species of concern not yet seen in Pohnpei, but you should be on the lookout for them.

• Cestrum nocturnum (Solanaceae). "Night-flowering cestrum" A shrub with white, bird-dispersed fruits that has escaped on Kauai in mesic forests. Forrms dense, impenetrable thickets.
• Miconia calvescens (Melastomataceae) "Purple Plague" Invasive Tree with very attractive large leaves, introduced as ornamental from tropical America, produces thousands of tiny bird-dispersed fruits at maturity. It has become the number one pest in French Polynesia since its introduction in 1937, now invading 2/3 of the forests of Tahiti. Also established on Maui, Oahu, and the Big Island in Hawaii. An incipient population was recently discovered on Kauai, but hopefully all the plants have been eradicated.
• Clidemia hirta (Melastomataceae) "Koster's Curse' Wirey stemmed shrub that has become one of Hawaii's worst pests in mesic to wet areas. Cli(lemia, Miconia, and other Melastomataceae species are proving to be the "kiss of death' for many native plant communities in Hawaii. Therefore, Introduction of all alien members of the Melastomataceae family should be prohibited on tropical islands, including the FSM, as they are proven to be highly invasive.
• Ligustrum (Oleaceae) "Privet" Avoid all species as several have proven invasive on oceanic islands.
• Lonicera japonica (Caprifoliaceae) "Japanese honeysuckle" This escaped ornamental vine is becoming a very serious pest in the upland mesic and wet forests of Kauai.
• Rubus moluccanus (Rosaceae). A heavily-armed, high-climbing brier with insipid fruits that has become established on Kosrae in wet lowland areas. It is one of the worst alien weed pests in the Mascarene Islands (SW Indian Ocean, so beware of this and all other Rubus species.

Of course, the list could be much, much longer. People have a natural tendency to introduce new plants, so the problem is ongoing and seems overwhelming at times. However, the government can help by not introducing species that have proven weedy on other tropical volcanic islands with similar habitats. Rapid elimination of small incipient weed populations, before they become widespread, is clearly the most effective means of control. And public awareness programs can be effective, but they must be ongoing and pervasive, not just one-time efforts.

lncidentally, there is a group here known as Hawaiian Ecosystems At Risk Working Group (HEARPWG). If you are interested in getting on board their email server, contact Philip Thomas: thomasp@maui.com

Botany home page
Lee Ling home
COM-FSM home page