Merremia peltata is a coarse climbing vine with underground tubers (FAO Technical Bulletin). Its stems are smooth and twine at the tips; they may be up to 20 metres long. Leaves are simple, alternate with purple veins beneath; leaf margins are waxy. White funnel shaped flowers are borne in clusters on stalks 15-30cm long (FAO Technical Bulletin). Leaves broadly cordate to orbicular, peltately attached, obtuse in general outline but very shortly and abruptly acuminate, strongly nerved; peduncles with a paniculate cyme of as many as 13 or more flowers; sepals glabrous, strongly concave or somewhat ventricose, to 2cm long, obtuse, only slightly accrescent but becoming very firm and hard in fruit; corolla white or yellow, 5-6cm long, ribs slightly glandular-puberulent without, broadly campanulate funnelform; capsule about 15mm long, splitting into many lanceolate valves; seeds dull brown, densely long-pilose. Both yellow and white-flowered forms are known (Fosberg and Sachet, 1977).

Merremia peltata is an invasive plant in the Pacific region, invading both dry lowland and mesic inland natural communities (Meyer 2000). Coastal, wetland, wet upland and cloud forests are less susceptible to colonisation and invasion by Merremia (Meyer 2000). In Samoa, this species occurs up to an elevation of around 300 metres, and thus only affects lowland ecosystems (Whistler 1995a, in Kirkham Undated). In Fiji it occurs from sea level to about 400 metres in forests and forest edges, on open hillsides and along roadsides; it becomes locally abundant and weedy on disturbed land (Smith 1991, in PIER 2005). M. peltata is also found in gardens, plantations, pasture and forest plantations.

This species increases its distribution and abundance in two ways, either vegetatively, by sprawling into neighbouring areas and rooting from its nodes or by seeds. Research in the Solomons islands indicates a low seed viability rate and creeping may be a primary mode of reproduction (Bacon 1982, in Kirkham Undated).

It is sometimes promoted as a means of providing rapid ground cover thus reducing erosion and nutrient losses following disturbance of land.

Merremia peltata crawls up and over forest tree species and thickets forming either a ground cover or canopy species; it smothers and strangles other vegetation. M. peltata has apparently been in the Pacific for hundreds of years (Whistler Pers. Comm., in Kirkham Undated) but has only become invasive in the years following tropical cyclones Ofa (1990) and Val (1991) according to comments from local government officials. Disturbance thus appears to be an ecological contributing factor to the invasive process for this species. On Samoa M. peltata invasion has been linked to several vectors of disturbance including the cyclones Ofa and Val, the expansion of taro plantations for export and food security and the subsequent taro blight.\r\n

Not all invasive plants causing problems are introduced and, interestingly, M. peltata is a plant noted for its invasiveness in part of its native range (including American Samoa). Both Merremia peltata (L.) Merr. and Merremia umbellata (L.) Hall. f. are aggressive native vines that are covering stands of native lowland rainforest in Samoa (Hanson 2004). Studied by itself, M. peltata suppresses species diversity and aids the spread of other vines such as Mikania micrantha when it forms a ground cover, however, it appears to support species diversity when grows in the canopy (Kirkham Undated). Furthermore, certain native pioneering tree species appear to be able to compete successfully with M. peltata, including the common lowland forest species Pometia pinnata which appears to be resilient to the vine (Kirkham Undated). When vegetation communities in Samoa are analysed on a landscape scale, plots dominated by M. peltata ground cover are more similar to lowland rainforest than plots dominated by non-native invasive ground cover (located in the coconut zone), which are more frequently disturbed by people and livestock and show a different successional pattern (Kirkham Undated). M. peltata thus appears to be a part of the succession of lowland rainforest recovery (Kirkham Undated).

Preventative measures: Since it requires full sunlight, minimizing disturbance will inhibit growth. A Risk assessment of Merremia peltata for the Pacific region was prepared by Pacific Island Ecosystems at Risk (PIER) using the Australian risk assessment system (Pheloung, 1995). The result is a score of 18 and a recommendation of: reject the plant for import (Australia) or species likely to be a pest (Pacific).

Integrated management: It is readily grazed by cattle, which can be used to control the weed. Non-grazed areas could be slashed, hand weeded or sprayed with 2,4 -D or glyphosate at recommended rates (FAO Technical Bulletin: Vanuatu).\"

Physical: One option is to exploit its shade intolerance and plant trees to shade it out (Kirkham Undated). This technique , however, is labor intensive in that not only will trees need to be planted, but they must be tended to prevent the vines from growing into the canopy. Hand control is difficult due to resprouting and rooting of stem fragments.\r\n

Since Merremia peltata requires full sunlight to grow, minimising disturbance will inhibit its growth. It is readily grazed by cattle, which can be used to control the weed. Non-grazed areas could be slashed, hand weeded or sprayed with 2,4 -D or glyphosate at recommended rates (FAO Technical Bulletin: Vanuatu). Herbicides as 2,4-D, dicamba, triclopyr, picloram and glyphosate are effective in controlling the weed. Trials have shown glyphosate to be an effective herbicide for use against Merremia spp., a major weed in forestry plantation areas of the Solomon Islands. Results indicate that 1.5kg a.i./ha would be sufficient (Miller 1982).Chemical: Where they can be applied, such herbicides as 2,4-D, dicamba, triclopyr, picloram and glyphosate are effective. \"\"Trials have shown glyphosate to be an effective herbicide for use against Merremia spp., major weed problems in forestry plantation areas of the Solomon Islands. Results indicate that 1.5kg a.i./ha would be sufficient\"\" (Miller, 1982).

\r\nBiological: In Samoa one option for management is simply to do nothing, and allow nature to take its course. As ground cover, M. peltata suppresses non-native weeds that would likely be present as ground cover in its absence (M. micrantha excepted). In the canopy, it helps to hand succession over from pioneer species to those more resembling climax species. Alternatively areas of M. peltata groundcover may be planted first with Macaranga harveyana and later with Cananga odorata, then following up with P. pinnata and other forest species. Scattering seeds, rather than establishing seedlings in nurseries, may be sufficient for this method. The low labor input and its self-maintaining strategy may make this a viable option.