Pittosporum undulatum Vent.Sweet pittosporum (Pittosporum undulatum) is native to eastern parts

of Australia. An evergreen tree with attractive fragrant flowers, sweet

pittosporum has been introduced widely as an ornamental plant to

North America, southern Africa, and many oceanic islands. It is reported

to be an environmental weed in its native Australia spreading beyond its

native range. It is known as an invader of many tropical and subtropical

mountain forests and in warm temperate regions of both hemispheres

and many islands.

Seeds are predominantly dispersed by birds and deposited at the base

of trees where they germinate soon forming a close dense canopy

dominating native vegetation. Seeds are not stored in the soil year to

year and are sensitive to temperatures as low as 90 degrees C. Prescribed

burns have been recommended as a control option; seed banks are

destroyed, growth rates reduced, as are seed dispersal and seedling

survival.

Sweet pittosporum was introduced to the Azores as a hedge plant to

protect orange tree plantations reportedly in the early 19th century. It is

listed as being one of ten most common woody plant species (trees and

shrubs) present in Azorean native forests and a major threat to Azores

native biodiversity. On San Miguel Island it is one of several plant species

that dominates native forests of Morella faya and Laurel azorica.Reference:Bellingham P. J., Tanner E. V. J., Healey J. R., 2005. Hurricane disturbance accelerates invasion by the alien tree Pittosporum undulatum in Jamaican montane rain forests. J Veg Sci 16:675–684 Gleadow, Roslyn M.; Narayan, Indira (2007) Temperature thresholds for germination and survival of Pittosporum undulatum: implications for management by fire. Acta Oecologica. 31(2). MAR-APR 2007. 151-157.Hortal, Joaquin; Borges, Paulo A. V.; Jimenez-Valverde, Alberto; de Azevedo, Eduardo B.; Silva, Luis, 2010. Assessing the areas under risk of invasion within islands through potential distribution modelling: The case of Pittosporum undulatum in Sao Miguel, Azores. Journal for Nature Conservation (Jena). 18(4). DEC 2010. 247-257.

Photo Credit: Forest and Kim Starr [link]

Sweet pittosporum is known to have spread to native forests in Jamaica

from the Cinchona Botanic Garden in 1883. The secondary forests that

are dominated by this introduced species consist of shrubs and early-

successional forest tree species. The displacement of native understorey

plant species has been partially attributed to allelopathic effect.

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