Pittosporum grows quickly and can shade out most other plants. Its decaying leaves produce a chemical that prevents other plants from growing under it. 

 

This is called an allelopathic affect.​

 

Many other Australian plants need fire for their seeds to geminate but the seeds of Sweet Pittosporum are eaten and spread by flying foxes and also by birds such as Currawongs.

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Introduced birds such Red-whiskered Bulbuls and Indian Mynas also spread the seeds.