Title: Pittosporum undulatum Vent.

Scientific Name:

Pittosporum undulatum Vent.

Common Names:

sweet pittosporum, Australian cheesewood



Source & more images (via ALA)

Habitat: Common in a variety of climates and habitat types, from moist sub-tropical to dry temperate, including wet and dry forest environments, riparian and coastal communities, rocky gullies and on bluffs and cliffs within range of severe salt spray (Binggeli and Goodland 1997, Gleadow 1983, Mullett and Simons 1995). Sweet pittosporum invades dry coastal vegetation, heathland and heathy woodland, lowland grassland and grassy woodland, dry sclerophyll forest and woodland, damp sclerophyll forest, wet sclerophyll forest, and riparian vegetation (Carr et al 1992).



Distribution:





Original source via CABI





Weed Assessment

ESTABLISHMENT


1. Germination requirements? "P. undulatum seedlings emerge after periods of wet weather." "Seeds may germinate after seed fall in spring, but most germinate in autumn." "Most seedlings at Langwarrin emerged in late autumn with the early rains, however, some also emerged in spring when the temperatures started to rise after winter." (Binggeli & Goodland, 1997; Blood, 2001; Gleadow, 1982).

2. Establishment requirements? "Full sun or light shade." (PFF, 2001).

3. How much disturbance is required? Invades undisturbed / minor disturbed natural ecosystems, e.g. heathland, sclerophyll forest & woodland, & riparian vegetation. "Much of the understorey in the relatively undisturbed forest of the Silvan water-catchment area consists, beside Pittosporum, of exotics such as holly (Ilex euripus), cotoneaster and Prunus species." (Carr et al., 1992; Gleadow, 1983).

GROWTH / COMPETITIVE


4. Life form? Tree; other (Carr et al., 1992).

5. Allelopathic properties? "The successful invasion of Pittosporum undulatum displacement of native understorey plant species has been partially attributed to allelopathic effects." (Turnbridge et al., 2000).

6. Tolerates herb pressure? "Following cutting of Pittosporum, it has a high capacity to resprout." "The ability of the seedling to recover suggests that if shoots were damaged the seedlings would be able to survive." (Goodland & Healey, 1996; Gleadow, 1982).

7. Normal growth rate? "P. undulatum becomes dominant in secondary forests & natural forest subjected to hurricane damage.In areas invaded by P. undulatum a sharp decrease in native species richness has been recorded." (Binggeli & Goodland, 1997).

8. Stress tolerance to frost, drought, w/logg, sal. etc? "Drought & frost resistant." "Shoots are able to resprout after low-temperature fires." "Succeeds in dry soils, Tolerates maritime exposure." (Bodkin, 1990; PFF, 2001; Gleadow, 1982).

REPRODUCTION


9. Reproductive system? Reproduces by seed, self and cross-pollination. "Seed and suckers." (Maiden; Blood, 2001).

10. Number of propagules produced? "The capsules usually contain 20 – 40 sticky orange seeds." "It is easily multiplied by seed, which is abundantly produced." Mature tree would easily produce >2000 seeds. "Large plants produce thousands of seeds annually." (Binggeli & Goodland, 1997; Maiden; Muyt, 2001).

11. Propagule longevity? "Fresh seed usually has a viability greater than 90%, but it declines significantly within two years." (Muyt, 2001).

12. Reproductive period? As a tree - not stated to be short-lived, etc. assumed to produce viable propagules for > 10 years.

13. Time to reproductive maturity? "Flowering starts at around 5 years of age." (Binggeli & Goodland, 1997).

DISPERSAL


14. Number of mechanisms? "Reproduces from seed with the help of birds who eat the fruit then excrete the seed, giving the plant excellent dispersal reliant upon the bird's range." (DPIWE, 2001).

15. How far do they disperse? Blackbirds main vector in Victoria - could disperse seed > 1km (Gleadow, 1982).


Impact Assessment

RECREATION


1. Restrict human access? An evergreen shrub or small tree with dense foliage, 4 – 14 metres tall. Capable of invading a broad range of habitats. Is used widely for hedges, ornament or windbreaks. Dense stands do occur in clumps and may be a nuisance to humans on foot. (Blood, 2001; Mullett & Simmons, 1995).

2. Reduce tourism? Where dense clumps occur in open forest they may be a minor nuisance to bushwalkers (Mullett & Simmons, 1995).

3. Injurious to people? No documented toxic or harmful physical properties.

4. Damage to cultural sites? Over time, clump enlargement can occur in some sites leading to almost monospecific stands. The consequent reduction in species diversity may create a negative visual effect (Mullett & Simmons, 1995).

ABIOTIC


5. Impact flow? Terrestrial species.

6. Impact water quality? Terrestrial species.

7. Increase soil erosion? The root system is variable and adapts to the type of soil. In sandy soils a taproot develops, while in clay soils the root system is diffuse and branched. With such a variable root system and the dense evergreen canopy the presence of P. undulatum is unlikely to contribute to soil erosion (Gleadow, 1982; Gleadow & Ashton, 1981).

8. Reduce biomass? In one study an infested site in a eucalypt woodland showed a decrease in cover and abundance of indigenous species from 100% to 10% when comparing a minimally infested area to one dominated by P. undulatum. Most of the species affected where understorey shrubs, herbs and grasses. Although clumped infestations may produce a dense evergreen canopy, it is possible that biomass may decrease slightly due to the reduction in the overall number of species (Mullett & Simmons, 1995).

9. Change fire regime? "Pittosporum undulatum is fire sensitive." Within its native range wildfire, amongst other natural controls, keeps pittosporum populations in check. "…natural and prescribed burns [in the forests of the greater Melbourne region] are controlled to the extent that fires rarely reach temperatures high enough to be fatal to P. undulatum." This suggests that P. undulatum of itself is not a highly flammable plant, and would thus have little impact on the intensity of fire. It is known to displace understorey species including grasses, and this may have an effect of reducing the frequency of fire. Negligible effect on fire risk (Mullett & Simmons, 1995).

COMMUNITY HABITAT


10(a) Impact on composition of high value EVC? EVC=grassy woodland (V); CMA=Corangamite; Bioreg=Otway ranges; VH CLIMATE potential Can lead to significant reduction on species diversity, particularly in lower and mid strata. Major displacement of dominant spp. within different layers. See comments at question 11 (Mullett & Simmons, 1995).

10(b) Impact on medium value EVC? EVC=herb-rich foothill forest (D); CMA=Corangamite; Bioreg=Otway ranges; VH CLIMATE potential See comment above.

10(c) Impact on low value EVC? EVC=riparian forest (LC); CMA=Corangamite; Bioreg=Otway ranges; VH CLIMATE potential See comment in 10(a) above.

11. Impact on structure? "The total cover and abundance of indigenous species was reduced from over 100% in quadrats where P. undulatum was minimal, to less than 10% in the central quadrats where P. undulatum cover was highest. Species diversity fell from a maximum of 25 species per quadrat to an almost complete floristic impoverishment." Mostly understorey spp. were affected. Major effect on lower and mid strata (Mullett & Simmons, 1995).

12. Effect on threatened flora? The spread of Pittosporum undulatum outside is native range is considered a potentially threatening process and has been declared as such under the Flora and Fauna Guarantee Act 1988. In particular it threatens the rare Forest Red Gum Grassy Woodland community in the lowland Gippsland plains (DSE, 1994).

FAUNA


13. Effect on threatened fauna? This species is not documented as posing an additional risk to threatened fauna.

14. Effect on non-threatened fauna? Over time and in the absence of management controls, the population density of P. undulatum increases, which has a known impact on reducing species diversity. In spite of the research undertaken to date on the impacts of the spread of P. undulatum no data is available to indicate how fauna is affected, if at all. Mullet (1999) suggests that, "…impacts of the floristic and structural simplification associated with P. undulatum invasion on faunal assemblages are unknown, but presumably substantial". Significant reduction in habitat for fauna possibly leading to reduce numbers (Mullet, 1999).

15. Benefits fauna? Native frugivorous birds are known to feed on the fleshy fruit, e.g. Pied Currawongs (Strepera graculina), Satin Bowerbirds (Ptilonorhynchus violaceus) and Silvereyes (Zosterops lateralis) (Mullet, 1999).

16. Injurious to fauna? No effect.

PEST ANIMAL


17. Food source to pests? "P. undulatum seeds from a large part of the diet of the introduced European blackbird (Turdus merula) during winter." Food source to minor pest species (Gleadow, 1982).

18. Provides harbor? The dense, evergreen canopy and bushy habit of the plant would likely provide for the pest birds that feed on the fruit.

AGRICULTURE


19. Impact yield? Not known as a weed of agriculture.

20. Impact quality? Not known as a weed of agriculture.

21. Affect land values? Not known as a weed of agriculture.

22. Change land use? Not known as a weed of agriculture.

23. Increase harvest costs? Not known as a weed of agriculture.

24. Disease host/vector? None evident in spite of extensive research undertaken for this species.




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Assessment ratings originally made by the Victorian Department of Primary Industries.
The entry of this assessment was made possible through the generous support of The Weed's Network.




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Date: 9 November 2009; 1:12:03 PM AEDT

Author Name: Michelle Heitch
Author ID: heitchm