Pacific Island Ecosystems at Risk (PIER)

Report on invasive plant species on Niue

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Dangerous species not known to be on Niue

Species that are invasive elsewhere and are likewise invasive or have the potential to become so on Niue

Species that are mentioned or listed as being weedy or invasive elsewhere and are common or weedy on Niue

Native and naturalized species exhibiting aggressive behavior

Strategies for dealing with invasive species


Appendix 1.  Background material and references

Appendix 2.  Species by category

Appendix 3. Other invasive plant species, mostly of agricultural concern, reported to be present in Niue

Appendix 4.  Invasive species present in American Samoa, the Cook Islands, Fiji, French Polynesia, Samoa or Tonga but not present in Niue

Appendix 5. Scientific name synonyms


Report to the Government of Niue on Invasive Plant Species of Environmental Concern


James C. Space and Tim Flynn

U.S.D.A. Forest Service

Pacific Southwest Research Station

Institute of Pacific Islands Forestry

Honolulu, Hawai‘i, USA

24 October 2000



Report to the Government of Niue on Invasive Plant Species of Environmental Concern

James C. Space and Tim Flynn (1)

The Government of Niue requested assistance from the US Department of Agriculture, Forest Service, Institute of Pacific Islands Forestry, to conduct a survey of invasive plant species of environmental concern, similar to surveys previously conducted in Micronesia and American Samoa. The survey was carried out from 15-19 May 2000. The objectives, as with previous surveys, were to: (1) identify plant species that are presently causing problems to natural and semi-natural ecosystems; (2) identify species that, even though they are not presently a major problem, could spread more widely or are known to be problem species elsewhere; (3) confirm the absence of species that are a problem elsewhere and, if introduced to Niue, could be a threat there; and (4) make appropriate recommendations.

During our visit local experts (2) showed us sites of known infestations. We also had available copies of botanical surveys conducted in the past (see Appendix 1, References). A visit of such short duration does not permit an exhaustive survey of the weed flora of the island. However, the intent was only to conduct an overall survey. Additional surveys of individual species or sensitive areas can and should be conducted as needed. This report summarizes our findings and makes some suggestions for further action.

Invasive species occurring in or of threat to Niue have been grouped into four categories:

  1. Species that are invasive elsewhere in similar ecosystems but were not seen on our visit and are not reported in the literature as being present on Niue (199 species).
  2. Species that are invasive elsewhere and are also invasive or potentially invasive on Niue (22 species).
  3. Species that are invasive or weedy elsewhere and are common, weedy or cultivated on Niue (97 species).
  4. Native species that exhibit aggressive behavior (1 species).

These species are listed in Appendix 2. Additional information about each species is located on a World Wide Web site,, and on the PIER-CD, copies of which have been made available to the Departments of Community Affairs and Agriculture, Forestry and Fisheries.

There are a number of other species that are mostly invasive weeds in gardens, fields, and pastures and along roadsides but don’t seem to pose any particular threat to wildland ecosystems. While we did not specifically survey for them, a list of these species, compiled from the literature, is included in Appendix 3.

1. Dangerous species not known to be on Niue

Perhaps because of its location "off the beaten path", many invasive species have yet to reach Niue. These are listed in Appendix 2, Table 1. The following list summarizes the worst of these.

Acacia farnesiana was reported by Waterhouse (1997) to be present but it was not seen and the local experts do not know of it. This species is invasive in Hawai‘i, Fiji, French Polynesia and Vanuatu and is reported to be present in the Cook Islands as well. If it should be found, it should be a high-priority candidate for prompt eradication. Other Acacias should be introduced only after due consideration of their possible invasiveness. The Acacia spirorbis planted as a yard tree on Niue appears to be only weakly invasive—only a few isolated examples away from houses were seen, and even those may have been on long-abandoned homesteads.

Cecropia obtusifolia and C. peltata are invasive tree species that are a problem in Hawai‘i and French Polynesia, respectively. Cecropia obtusifolia is also reported to be invasive on Rarotonga (Cook Islands).

Chromolaena odorata (Siam weed) is a highly invasive pan-tropical weed. It will likely show up in Niue at some point in time and should be promptly eradicated if found. It has tiny seeds that can travel on boots, clothing or used cars or equipment. Biological controls are available but are most effective in open areas, less so in shaded stands.

Clerodendrum quadriloculare is suspicious because it appears to have the ability to invade intact or relatively intact native forests. This species is notorious for being a prolific producer of root suckers and, in fact, the plant is easily propagated by means of root cuttings. A dense, monospecific understory of this species was seen growing in full shade beneath the forest canopy on Pohnpei. The species is an attractive yard plant and is commonly planted for that purpose. Cultivated specimens were observed in American Samoa and French Polynesia. In Hawai‘i it is becoming a problem ornamental, producing numerous root suckers that appear some distance from the parent plant.

Cinnamomum verum (cinnamon) was found to be very invasive in our survey of American Samoa. It is also present in Samoa, Fiji, French Polynesia and the Cook Islands (Rarotonga).

Clidemia hirta (Koster’s curse) is a serious problem species in Hawai’i and other locations. It is reported by Waterhouse (1997) to be present in Niue. This is doubtful, as we did not see it. This is a very serious weed of the forest understory on many tropical islands and should be immediately eradicated if found. It is present in Samoa and American Samoa, Tonga and Vanuatu.

Coccinia grandis (ivy or scarlet gourd) is a smothering vine that is showing potential for serious damage to the forests of Saipan. The vines climb over trees and form such dense cover that the forest underneath is completely shaded out and destroyed. It is also invasive in Guam and Hawai‘i and is reportedly present in Fiji, Tonga and Vanuatu. It is a vegetable commonly used in southeastern Asian cooking and the plant is often introduced for that reason.

Cordia alliodora (Ecuador laurel, salmwood) was introduced to Vanuatu as a forestry tree and has become a pest there (Tolfts, 1997).

Cryptostegia grandiflora (rubber vine, India rubber vine) is a climbing vine that has become a serious problem in northeastern Queensland, Australia. Other vines that could be serious problems if introduced into Niue include Thunbergia species, Passiflora species not already present and non-native Ipomoea species.

Dieffenbachia seguine (spotted dieffenbachia or dumb cane), a common house and yard plant, is apparently absent although D. picta was reported by Sykes (1970) to be under cultivation in Alofi. This species is a problem in American Samoa and is reportedly present in the Cook Islands, Fiji, and Tonga. If found in the wild, either of these species should be promptly eradicated, as they reproduce vegetatively and can thrive in the dense shade of an intact native forest canopy.

Two rubber trees, Funtumia elastica (African rubber tree) and Castilla elastica (Panama rubber tree), are species that have proven very invasive in Samoa. Castilla elastica is present in French Polynesia as well.

Miconia calvescens (the purple plague) has been a disaster to the forest ecosystem of Tahiti in French Polynesia (and has subsequently spread to other islands in French Polynesia). It has also escaped in Hawaii and is the subject of an intensive and costly eradication effort there. It recently was discovered in Queensland, Australia, were an eradication project is also under way. This species is an attractive garden plant and might be introduced this way or as tiny seeds on shoes or used equipment.

A number of grass species are potentially invasive, including:

Passiflora tarminiana (banana poka, banana passionfruit; formerly known as P. mollissima), a smothering vine that is a problem in Hawai‘i and New Zealand, is also absent.

Pithecellobium dulce (Madras thorn) is a thorny tree present in Hawai‘i, Fiji and French Polynesia.

Psidium cattleianum (strawberry guava) is a small tree that forms dense thickets. It is a major problem species in a number of island ecosystems including Hawai‘i, Fiji, Tahiti and Rarotonga and Mangaia in the Cook Islands. Varieties with red and yellow fruits are known.

Tibouchina herbacea (glorybush or cane ti) is another species that is a major problem in Hawai‘i.

The best indicator that a species might be invasive is the fact that it is invasive elsewhere. However, each island ecosystem is unique and invasiveness cannot be predicted with certainty. A good strategy is to be extremely cautious and exclude these and other species known to be invasive or weedy elsewhere (although the best strategy is to exclude all species not shown by risk assessment to be of acceptable risk). These and other known problem species that have the potential to cause problems in tropical island ecosystems and are not yet present in Niue are listed in Appendix 2, Table 1. These species should be excluded through plant quarantine and, if establishment is detected, promptly evaluated for eradication. In addition, species that are reported to be present in the Cook Islands, Fiji, Samoa and American Samoa and Tonga but are not present in Niue are listed in Appendix 4. These species would be of high risk of introduction from any air and ship traffic between these points and Niue.

2. Species that are invasive elsewhere and are likewise invasive or have the potential to become so on Niue

Some known invasive plants that are causing trouble in similar ecosystems have been introduced into Niue (Appendix 2, Table 2). Some of them are already causing problems while others are not. Some are cultivated plants that have not (yet) escaped and their potential for causing damage is so far unknown. However, one of the best predictors of invasiveness is the behavior of the species elsewhere, and these are known troublemakers.

Adenanthera pavonina (pomea, coral bean tree), invasive in secondary forests throughout the Pacific, is fairly widespread (and not native) on Niue. It is quite invasive on Tutuila, American Samoa. It may have not yet reached its full potential on Niue.

Aspargus setaceus was seen at the entrance to the Matavai Resort and at a few other locations. This species is a weed in Hawai‘i. Its seeds are spread by birds, so it has the potential to spread widely.

Occasional infestations of Clerodendrum chinense (Honolulu rose) were seen. It is a problem species in Hawai‘i, Samoa and American Samoa, so has the potential to spread more widely. It is reportedly controllable through repeated cutting or mowing (per Tom Misikea).

Epipremnum pinnatum cv. 'Aureum' [=Scindapsus aureus], a climbing vine with large green and yellow leaves, is present at quite a number of locations. It forms a dense mat on the forest floor as well. Spread by cuttings, it is difficult to eradicate as any roots or pieces left behind will sprout.

Hemigraphis alternata (metal leaf) was seen in several locations. This species is shade tolerant and will spread in the forest understory. It is found mostly along roadsides where cuttings have apparently been dumped. Two other species with similar behavior are Tradescantia spathacea (talotalo, laupapaki) and T. zebrina (wandering jew).

Leucaena leucocephala (pepe) was quite prevalent, but not as aggressive as expected.

Lonicera japonica (Japanese honeysuckle) was seen cultivated in several locations. This species is a serious pest in a number of countries, is on the New Zealand noxious weed list and is banned from sale in that country. It can be spread both by birds and cuttings.

Macfadyena unguis-cati (cat’s claw creeper) was seen beside the Public Works building. This aggressive vine climbs trees and also forms a dense mat on the ground. Control is difficult because it has tuberous roots and reproduces from pieces and cuttings. It is a problem species in Hawai‘i.

Melinis minutiflora (molasses grass) is a species that is both invasive and can cause a serious fire hazard. It has fostered the establishment of fire regimes on many islands where it has been introduced. It is not widespread on the island.

Merremia tuberosa (wood rose), a climbing, smothering vine, is notable for its aggressive behavior on Niue. It is present in a limited number of locations—good examples can be seen at the dump and behind the library/archives building.

Mikania micrantha (mile-a-minute weed) is pervasive throughout the island.

Mimosa diplotricha [=invisa] is a particularly nasty plant as it is covered with thorns and forms dense tangles that are difficult to walk through. It is limited in distribution on Niue (in the Talafa area) and has been treated for eradication (sprayed with Roundup®). Given the limited extent of the infestation and the problems this species can cause, completion of the eradication effort should be given high priority. Mimosa pudica, a smaller plant with only small prickles, can form dense mats. It doesn’t seem to be widespread yet, but it may become more prevalent with time.

Occasional trees of Paraserianthes falcataria [Falcataria moluccana] (Molucca albizia) were seen. This species has the potential, over time, of spreading more widely (as can be seen on Hawai‘i, Pohnpei and Tahiti). Further planting should be discouraged. If this is not a desired species, emphasis could be given to cutting the existing trees.

Passiflora foetida (love-in-a-mist) was fairly widespread. It is quite prevalent on most Pacific islands.

Pennisetum purpureum (elephant grass) forms dense stands and is the most troublesome grass on Niue.

Solanum torvum (prickly solanum, devil's fig) is a spiny species of disturbed areas that forms dense, impenetrable thickets. It was reported to be present on Niue, but was not seen. If previously present, it may have already been eliminated, but if not it certainly must be of limited extent and would be a candidate for eradication. It would be a serious problem for agriculture.

Sorghum sudanense (Sudan grass) was found along the road at the west end of the airport runway, along with a similar, as yet unidentified species. It was also seen elsewhere, such as along the Alofi-Hakapu road. Sudan grass has a reputation of being quite invasive, and may be another invasive species yet to reach full potential on Niue. It is reported to be present in Tonga. [Note:  This plant was subsequently identified as Sorghum arundinaceum (Desv.) Stapf.]

Spathodea campanulata (African tulip tree) is occasionally planted as an ornamental. This tree has become a major problem in Fiji, the Hawaiian Islands and some other places. Large trees do not stand up well to wind. At least at the Vaipapahi Experimental Station it has begun to spread locally by what appear to be root suckers. This species should be carefully monitored and any further planting should be discouraged.

Stachytarpheta cayennensis [urticifolia] (blue rat's tail) is ubiquitous and Stachytarpheta jamaicensis is present as well. Both species are widespread in the Pacific.

Syngonium angustatum, a climbing aroid, is probably another escape from cultivation. It has the ability to spread in the deep shade of intact forests, forming a dense mat on the forest floor as well as climbing trees (behavior similar to Epipremnum pinnatum cv. 'Aureum'). It is difficult to eradicate as it is able to reproduce from a single node and bits and pieces of the stems or roots are easily overlooked. It spreads from dumped cuttings.

Tillandsia usneoides (old man’s beard, Spanish moss) is widely cultivated as a yard plant. It is a native of the southern United States, where it is widespread. Given the warm, moist climate of Niue, it has the potential to spread out of cultivation.

Tithonia diversifolia (tree marigold, Mexican sunflower) is widespread along roadsides but it’s a light-loving species and probably won’t penetrate far into the forest.

Wedelia [Sphagneticola] trilobata (Singapore daisy) has the potential to become a widespread pest, as on many Pacific islands. Since distribution is presently limited, it might be considered seriously for control or eradication.

3. Species that are mentioned or listed as being weedy or invasive elsewhere and are common or weedy in Niue

A large number of other common or weedy introduced species were noted. Many of these species, which might best be termed aggressive weeds, are mostly prevalent along roadsides or on disturbed sites, although some species, particularly alien trees, can gradually spread into forested ecosystems. In the case of vines and plants that form dense ground cover, the regeneration of native species can be inhibited.

Some of these species could become a problem in the future, since there is often a long lag time between introduction and when a species begins to cause serious impacts. These species (listed in Appendix 2, Table 3) should be monitored for spread and possible control measures, if necessary.

Not many exotic tree species have been introduced to Niue. Some that are present and might spread beyond cultivation include Bauhinia monandra (orchid tree), Ceiba pentandra (kapok), Delonix regia (flame tree), Moringa oleifera (horseradish tree), Samanea saman (monkeypod), Tecoma stans (yellow bells) and Thevetia peruviana (yellow oleander), but these should be easily controlled if they appear in unwanted places.

A number of introduced grasses have become established, including Axonopus fissifolius (narrow-leaved carpetgrass), Cenchrus ciliaris (bufflegrass), Cenchrus echinatus (bur grass); Chloris radiata (plush-grass, radiate fingergrass), Chrysopogon aciculatus (Mackie’s pest, lovegrass), Cynodon dactylon (Bermuda grass), Digitaria ciliaris (fingergrass, smooth crabgrass), Digitaria violascens (smooth crabgrass), Eleusine indica (goosegrass), Panicum maximum (Guinea grass), Paspalum conjugatum (Hilo grass), Paspalum dilatatum (dallis grass), Sorghum halepense (Johnson grass), Urochloa mutica (para grass) and Urochloa subquadripara (green summer grass).

Other widespread or weedy species include Abelmoschus moschatus (fou ingo), Allamanda cathartica (yellow trumpet vine), Asystasia gangetica (Chinese or Philippine violet), Bidens pilosa (beggar’s tick), Centrosema pubescens (centro), Crotalaria micans (pine kotalelia), Cuscuta campestris (golden dodder), Derris malaccensis (akau Niukini, New Guinea creeper) and Furcraea foetida (Mauritius hemp).

Antigonon leptopus (chain of hearts), a climbing vine often planted as an ornamental, is a widespread pest on Guam. Only a few examples, mostly in cultivation, were seen on Niue.

A climbing vine, tentatively identified as Ipomoea macrantha, was seen next to Gabe’s Food Bar and at other locations. Ipomoea macrantha is indigenous, but a specimen was taken and a positive identification is pending.

Lantana camara (lantana) is present but is apparently fairly well controlled by introduced biological agents. If lantana becomes a problem an evaluation should be conducted to make sure these agents are still present.

Momordica charantia (bitter-melon, balsam pear), a member of the cucumber family, is a climbing vine and its fruit can be the host for fruit flies. It is reported to be present but was not seen.

4. Native and naturalized species exhibiting aggressive behavior

Merremia peltata (fue, fue vao), a native or early introduction, is quite invasive along forest edges where there has been disturbance, but its extent seems to be limited on Niue, unlike many Pacific islands.

Strategies for dealing with invasive species

The first line of defense against invasive species is to keep them out. Control at ports of entry is essential, and those concerned with the protection of natural ecosystems should work closely with plant protection and quarantine officials to combat known and potential invasive plant species. Plant quarantine officers should be familiar with both agricultural pests and those that threaten wildland ecosystems. A list of known noxious species to be excluded should be developed and exclusion of these species should be backed by the force of law and regulation. Better yet is to utilize the "precautionary principle" (now used by Australia and New Zealand and under serious consideration by a number of other counties) to exclude all alien species not shown to be of acceptable risk. Risk assessment and management techniques can be used to assess the likelihood and effects of possible introductions and to develop exclusion and eradication strategies.

Niue is to be commended for the recently formed Invasive Species Committee. Close coordination and cooperation between the various government Departments and Divisions is essential. The committee can be effective both for long-term strategic actions, such as review and strengthening of relevant laws and regulations, as well as short-term tactical and operational problems, such as the introduction of a new species.

The Invasive Species Committee should consider drawing up a prioritized plan of action. This would include critical areas to be protected and species that might lend themselves to control or eradication. Time, money and people are always in limited supply and they must be directed to the places where they will do the most good. There are many areas on the island that are relatively free of weed species. It should be possible to eliminate the invasive species of major concern in at least some of these areas and protect them into the future. Some recommendations are made below as to possible management actions against some individual plant species, but the Committee should test these against available resources and priorities.

Education of the public about the danger of introductions and encouraging the use of native species can be helpful. People need to understand why they should follow the quarantine regulations, why they shouldn’t dump garden cuttings in the woods, and why they should report suspicious plants. What may just be a pretty flower to be planted in a yard or garden can turn out to be an invasive species. Public service announcements on television or radio can be used and "wanted" posters can be prepared for critical species. Education of schoolchildren is especially important, as this is the most impressionable age. Children can also have a notable effect on the actions of their parents. Prompt follow-up to public reports and inquiries is essential to maintain the credibility of a public education program.

The public also needs to understand that the immediate eradication of a small area of a problem species, even if it involves the use of herbicides, may be better than living with a problem species forever. There are many instances where you hear people say, "I wish we'd taken action when this pest was first noticed". It may even be worthwhile to take people to a place where they can be shown the full extent of a problem if the infestation is allowed to spread so that they will understand, accept and support eradication. For example, anyone visiting Tahiti would very likely come away convinced that Miconia calvescens is an ecological disaster and that it should be prevented from becoming established on other Pacific islands. The public should be informed and involved in any proposed control or eradication actions.

Any local nurseries, botanical gardens or plant importers can be sources of new introductions. A positive approach is to work together to develop a "white list" of both native and non-native species that the public can be encouraged to plant.

Foresters, conservation officers, extension agents and others that spend time in the field should be alert to new species that exhibit invasive behavior. Often, these species first show up in urban or farm areas because they are usually introduced by people and tend to first become established in flower gardens and disturbed areas. Suspicious plant species should be promptly reported. Periodically scheduled surveys can also be conducted for new or expanding infestations. An evaluation should be conducted for any new species that appears to be invasive or is known to be invasive elsewhere. Assistance by an expert who is familiar with the species and methods for its eradication or control should be requested if needed. Prompt action is essential, since once a species becomes widespread, control or eradication can be extremely costly or impossible. Assistance is also available on-line from experts through the Pacific Pestnet and Aliens list-servers.

Niue appears to have adequate laws and regulations in place to deal with quarantine and new introductions, but it would be appropriate for the Invasive Species Committee to review them to see if they might need to be strengthened. In the case of Niue, where most land is privately owned, the ability of government to require the control of noxious species on private lands or to take action on private lands if the landowner cannot be located or does not take prompt action is essential. Provision for emergency funds to deal with immediate problems should also be in place. New Zealand and some of its town councils have strong laws and regulations that can be used as models.


In addition to the above general strategies, we offer the following specific recommendations:

Appendix 1.  Background material and references

Appendix 2.  Species by category

Appendix 3. Other invasive plant species, mostly of agricultural concern, reported to be present in Niue

Appendix 4.  Invasive species present in American Samoa, the Cook Islands, Fiji, French Polynesia, Samoa or Tonga but not present in Niue

Appendix 5. Scientific name synonyms

(1)  Former Director, Pacific Southwest Research Station, USDA Forest Service (now retired) and Curator of the Herbarium, National Tropical Botanical Garden, respectively.

(2)  We would like to sincerely thank Colin Etuata, Crispina Fakanaiki and Sheila Utalo, Department of Agriculture, Forestry and Fisheries, for their generous assistance in the conduct of the survey.

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This page updated 13 February 2001.