Sweet pittosporum (Pittosporum undulatum)
Very High Risk Weed for Kangaroo Island
An Alert Weed for Kangaroo Island. Notify the Kangaroo Island Landscape Board. Early detection and control are the best way to prevent the next widespread weed.
It is a declared plant for South Australia.
THE SITUATION AND WHAT TO DO
Sweet pittosporum is a fast-growing evergreen tree native to eastern Australia but widely planted as a garden, screening and street tree. Through cultivation it has spread outside its natural range and become an environmental weed in many regions, including parts of South Australia where it invades native bushland and sheltered forests.
Sweet pittosporum is a declared pest plant in South Australia under the Landscape South Australia Act 2019.
It commonly establishes along roadsides, gullies, disturbed bushland, and urban reserves where birds disperse the fruit. Seeds are spread mainly by fruit-eating birds and other animals, but also through dumped garden waste, contaminated soil, and occasionally on footwear or vehicles.
On Kangaroo Island occasional and widespread infestations related to garden plantings have been found across much of the island with new infestations being found every year.
A significant effort is going in to find and controlling this emerging weed and protecting sites. You can help by:
- Identify and remove young plants early before they produce fruit.
- Avoid dumping garden waste in bushland or reserves.
- Dispose of fruiting material carefully to prevent seed spread.
- Control mature trees and monitor sites for seedlings for several years after removal.
- Reporting any sightings to the Kangaroo Island Landscape Board.
DESCRIPTION
Growth form: evergreen shrub or small tree usually 4–15 m tall with a dense rounded canopy that creates heavy shade beneath the plant.
Leaves: glossy dark green leaves, usually 6–17 cm long, oval to obovate with distinctive wavy margins and paler undersides. Leaves are often clustered near the ends of branches.
Flowers: creamy-white, bell-shaped flowers with a strong sweet fragrance, typically appearing from late winter to spring.
Fruit: round capsules or berries that turn orange when mature and split open to reveal bright orange-red sticky seeds.
Seed: Fruit usually contain 20–30 seeds, and mature trees can produce thousands of seeds each year. fresh seed can have around 90% viability, but viability generally declines after 1–2 years and most seeds survive less than about five years in the soil.
IMPACTS
Sweet pittosporum can invade native vegetation and form dense stands that shade out native plants and reduce biodiversity. Its thick canopy and heavy leaf fall suppress other vegetation and may alter soil nutrients, allowing it to dominate bushland areas. These infestations can change habitat structure and reduce the diversity of native plants and animals.
CONTROL OPTIONS
Management focuses on preventing seed production and removing established plants. Small seedlings can be hand-pulled or grubbed out when the soil is moist. Larger plants are commonly controlled using cut-stump, drill-and-fill, or basal bark herbicide treatments (e.g., glyphosate or triclopyr formulations).
Follow-up monitoring is important because seedlings often emerge from the soil seed bank after mature trees are removed.
Maintaining healthy native vegetation and avoiding disturbance or dumping of garden waste helps prevent reinfestation.
No biological control agents are currently available.
Permitted and on-label herbicides and rates can be found on the PIRSA Weed Control Website:
DECLARATIONS
Sweet pittosporum is declared under the following sections of the Landscape South Australia Act 2019:
- 188(1) Prohibiting sale of the plant
- 188(2) Prohibiting sale of contaminated goods
- 192(2) Landowners to control the plant on their properties
- 194 Recovery of control costs on adjoining road reserves
FURTHER INFORMATION
- Declared Plant Policy - pir.sa.gov.au
- Early Intervention Handbook - pir.sa.gov.au
- Weeds Australia weeds.org.au