Introduction:
Australian cheesewood (Pittosporum undulatum) Weed Bush.
Pittosporum undulatum is an evergreen tree that is often used as an ornamental plant, due to its attractive fragrant flowers. It is native to south-eastern Australia but has now spread to a number of islands in the Pacific and Caribbean, as well as islands in the Atlantic and to South Africa. It is also invasive In Australia outside its native range. Research is being carried out in Jamaica to determine the most effective methods of control for this species.
Description:
A slender-branched shrub or tree, can grow to 12m tall in its natural habitat, with smooth, gray bark. It has a straight bole, regular whorls of branches, and a dense crown. Leaves alternate, often crowded at ends of slender, light brown branches, 6-15cm long, 1.5-4cm wide, lanceolate, pointed at both ends, shiny, with prominently wavy margins. Flowers almost white, few, fragrant, borne on the youngest branches in terminal clusters about 2-3cm long; petals 5, abruptly bent downward at end. Fruit globe-shaped, compressed, usually 16mm long, leathery, about 25-seeded. Seeds angular, 3mm long and 1mm thick, dark brown, smooth. In Jamaica this species has a maximum recorded height of 22m (also a Diameter Breast Height (DBH) of 65.6cm and a wood density of 0.8-1.0 g cm-3).
Occurs in:
Natural forests, range/grasslands, riparian zones, ruderal/disturbed, scrub/shrublands.
Habitat description:
Pittosporum undulatum is native to the coastal belt and mountains of south-eastern Australia. Prefers moist to wet areas in rainforest gullies and sclerophyll forest. Can grow to 1200m in elevation. Takes advantage of disturbance, as shown in Jamaica, where it was able to dramatically increase its range after Hurricane Gilbert struck in 1988. In Jamaica it has been recorded to 1740m altitude. Appears to adapt to high nutrient soils better than other plant species, allowing it to outcompete them in human-modified habitats. Able to tolerate maritime exposure.
P. undulatum exhibits great versatility: as a coloniser of open/disturbed habitats, as well as being very shade tolerant, casting a dense shade. It supports a dense seedling bank and soil seedbank and has a good capacity to resprout after cutting.
Distribution Map:
Australian cheesewood (Pittosporum undulatum) Distribution shown in Green.
General impacts:
The leaves contain toxins that can inhibit the growth of other plants (Bushcare, 2003). Invades native forest areas and can shade out native plants.
Geographical range:
Native range: south-eastern Australia.
Known introduced range: Guam, Hawai‘i, New Zealand, Lord Howe Island, Norfolk Island, Canary Islands, Jamaica, South Africa, Cuba, French Polynesia, St. Helena. Also present in continental Portugal, the Azores and Madeira.
Local dispersal methods:
Consumption/excretion: The seeds are spread by frugivorous birds.
For ornamental purposes (local): The attractive flowers of P. undulatum mean that it is often used as an ornamental tree.
Management information:
Close up of Australian cheesewood (Pittosporum undulatum) Weed Flowering.
Preventative measures: A Risk Assessment of Pittosporum undulatum for Hawai‘i and other Pacific islands was prepared.The alien plant screening system is for use in Pacific islands. The result is a score of 7 and a recommendation of: “Likely to cause significant ecological or economic harm in Hawai‘I and on other Pacific Islands as determined by a high WRA score, which is based on published sources describing species biology and behaviour in Hawai‘I and/or other parts of the world.”
Physical: Research on management options for P. undulatum has been undertaken in Jamaica, where it is a serious problem. Uprooting seedlings by hand is successful, but they must be disposed of properly, as they will reshoot if left lying on the ground. Bark stripping is effective in preventing sprouts, but only if all bark, from 0.3m down to soil level, is removed.
Chemical: In South Africa a mixture of 2,4,5-T and diesel has proved effective when applied to stumps cut above ground level. Applying concentrated Roundup® (glyphosate) to cut stumps has also worked in Australia, as has injecting glyphosate into holes drilled in plant stems. Glyphosate is recommended as a herbicide because of its effectiveness and low risk to human and environmental health.
When managing P. undulatum in heavily infested areas consideration must be given to the effects of its removal. The eradication of a large number of trees may facilitate an invasion by undesirable non-woody plant species that thrive in disturbed areas.
