From: David H. Lorence <firstname.lastname@example.org>
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.
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
- 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
Botany home page
Lee Ling home
COM-FSM home page