Invasiveness Assessment - Peppercorn tree (Schinus molle) in Victoria

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Plant invasiveness is determined by evaluating a plant’s biological and ecological characteristics against criteria that encompass establishment requirements, growth rate and competitive ability, methods of reproduction, and dispersal mechanisms.

Each characteristic, or criterion, is assessed against a list of intensity ratings. Depending upon information found, a rating of Low, Medium Low, Medium High or High is assigned to that criterion. Where no data is available to answer a criterion, a rating of medium (M) is applied. A description of the invasiveness criteria and intensity ratings used in this process can be viewed here.

The following table provides information on the invasiveness of Peppercorn tree.
A more detailed description of the methodology of the Victorian Weed Risk Assessment (WRA) method can be viewed below:

Victorian Weed Risk Assessment (WRA) method (PDF - 630 KB)
Victorian Weed Risk Assessment (WRA) method (DOC - 1026 KB)
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Common Name: Peppercorn tree
Scientific name: Schinus molle

Question	Comments	Rating	Confidence
Establishment
Germination requirements?	‘Although S. molle seed has no innate dormancy, cold temperatures in winter and drought in summer enforce dormancy for most of the year. (Howard & Minnich 1989)’. Seeds are described as taking 20-30 days to germinate under cooler temperatures and although less time, e.g. 10 days, in warmer temperatures, require sustained surface soil moisture to germinate without desiccation which is unusual. S. molle is described as having a ‘low germinative capacity’ (Howard & Minnich 1989) and appears to require reasonably unseasonal events for germination.	ML	MH
Establishment requirements?	Described as growing in forests (Weber 2003, Carr et al 1992) and ‘…survives nearly everywhere it is planted (Howard & Minnich 1989)’. However, germination and seedling surviving are described as ‘the major bottleneck to establishment’. Appears to be some conflicting information regarding its establishment requirements.	M	MH
How much disturbance is required?	Although often associated with disturbed and degraded environments (Muyt 2001), it appears also able to establish in minor disturbed natural ecosystems. For example, ‘S. molle becomes established on the periphery of densely vegetated riparian habitats (Howard & Minnich 1989)’ and Carr et al (1992) documents it occurring in lowland grassland, grassy woodland, dry sclerophyll forest/ woodland & rock outcrop vegetation.	MH	H
Growth/Competitive
Life form?	Tree (Howard & Minnich 1989).	L	H
Allelopathic properties?	Leaves and fruit strongly inhibitory to seed germination and seedling growth of cucumber and wheat (Anaya & Gomez-Pompa 1971). Allelopathic properties seriously affecting some plants.	MH	MH
Tolerates herb pressure?	‘Not normally grazed by animals (Blood 2001)’. Anacardaceae in general are known for their toxic compounds and S. molle in particular is infrequently eaten by goats or insects (Fuentes et al 1983). However it is described as being consumed by sheep (Salem et al 2005), the Emperor Gum moth (French 1945) and sometimes (seedlings) rabbits (Fuentes et al 1983). Likely to be consumed but not preferred.	MH	H
Normal growth rate?	Available information on growth rate is somewhat contradictory, with growth and spread appearing to vary in different locations. Seedling growth is described as both rapid (Howard & Minnich 1989) and as very slow, until the root system is firmly established. (Blood 2001). However it is also generally described as being ‘fast growing (Weber 2003, Blood 2001)’. Overall it is likely to have a moderately rapid growth rate.	MH	MH
Stress tolerance to frost, drought, w/logg, sal. etc?	Mature trees very resistant to fire and drought (Blood 2001). Limited by extreme frost, but some tolerance likely as grows in the Andes to 3,300 m (Howard & Minnich 1989). Occurs on coastal dunes and beaches (Weber 2003). Tolerant of poor soils and poor drainage (PIER 2001), occurring in seasonally wet areas. Once established seedling mortality is described as rare (Howard & Minnich 1989). Highly resistant to drought and fire, some tolerance to frost, waterlogging and salinity.	H	MH
Reproduction
Reproductive system	Reproduces both sexually and vegetatively via ‘Seed and suckers (Blood 2001)’.	H	MH
Number of propagules produced?	Large tree with ‘huge quantities of seed set (Blood 2001)’ and fruits continuously throughout the year (Howard & Minnich 1989). Images indicate an individual would produce many more than 2,000 seeds (Blood 2001, Muyt 2001).	H	H
Propagule longevity?	Seeds remain viable for less than 3 years (Cal-IPC2003). ‘Seeds ripening during summer heat and drought can remain viable until the rainy season (Howard & Minnich 1989)’, also indicates short viability.	L	H
Reproductive period?	Howard & Minnich (1989) describes ‘large old trees’ as setting huge quantities of fruit. Presumed to produce propagules for > 10 years.	H	H
Time to reproductive maturity?	Takes more than 2 years to reach reproductive maturity (Cal-IPC 2003).	ML	M
Dispersal
Number of mechanisms?	‘Seed is dispersed by birds, mammals and water (Howard & Minnich 1989)’.	H	H
How far do they disperse?	‘Seeds are widely dispersed by birds (Howard & Minnich 1989)’. Potential for seeds to disperse greater than 1 km.	H	H

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