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.
• 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.
• 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.
• 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.
• 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.

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

Plants seen on the Fall 1999 walk:

• Acacia auriculiformis: a tree that spreads by suckers
• Ageratum conyzoides. Pwisehn kou (cow dung weed).
• Albizia lebbeck. An alien species but not considered an aggressive alien. Light wooded tree used for chop sticks in Asia.
• Bidens alba: Begggar's tick.
• Chromalaena odorata. Pohnpeian: wisolmat.  Global in distribution. Locally known as wisin mat en rere, but don't say that out loud on Pohnpei. Possibly came in on a tractor, maybe in dirt in its treads, spread around the island when the road was bulldozed.
• Clover vine.
• Commelina diffusa, a member of the wandering jew family. Note leafy bract under the flower.
• Eleusine indica, a grass known locally as reh takai.
• Invasive Ipomea spp.
• Ischaemum polystachum: Invasive grass introduced by Japanese. They thought it might be useful for cattle food but NOT!
• Mangifera indica: mango. Potentially invasive!
• Melastoma malabathicum: A native plant
• Mimosa pudica. Sensitive plant. Invasive. Worse: Mimosa invisa. The later forms impenetrable thorn thickets.
• Nara. A member of Ficus. Not invasive on Pohnpei.
• Pennisetum: brought in by the Japanese who mistakenly believed cattle would eat it.
• Spathodea campanulata: African tulip tree. Birds spread the seeds. Very aggressive tree.
• Wedelia trilobata: brought from Hawaii by women down at the Catholic mission around 1970 who thought it would look nice in their gardens. All over the island now. Possibly allelopathic.

Combatting invasive species: Watch for plants that are new to Pohnpei and that spread rapidly. Destroy all plants as soon as it appears it might be aggressive. Wedelia trilobata came to the island as a single plant - how easy it would have been to wipe it out back then. Now it is beyond control. On your own land you can, with a few years of hard work, remove all of it. But the plant will never be gone from the island.

Site with a more complete list of invasives: http://www.hear.org/pier/pohnpei.htm

NOTE: The common names in this table includes those in use at various locations throughout the Pacific and elsewhere. Additional information, including the locations where the various names are used, can be found in the individual species summaries.

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