Invasiveness Assessment - Tree tobacco (Solanum mauritianum) 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 Tree tobacco.

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: Tree tobacco
Scientific name: Solanum mauritianum

Question	Comments	Rating	Confidence
Establishment
Germination requirements?	Seeds from ripened fruits have an initial dormancy period, while seed from green fruits however will germinate within 50 days at a range of temperatures (Florentine, Craig & Westbrooke 2003). The plant can produce fruit through out the year (Drew & Hooper 1983). While most of this data comes from tropical climates, there appears not to be any specific requirements for germination of S. mauritianum.	H	MH
Establishment requirements?	There is conflicting reports on this point, Chandler (1981) states that seedlings are completely intolerant of shade. Its ability to invade intact vegetation including riparian vegetation and forest however would suggest tolerance of at least moderate shade (Blood 2001; Raghu et al 2004).	MH	MH
How much disturbance is required?	Able to invade intact native vegetation including grassland, and grassy woodland (blood).	MH	MH
Growth/Competitive
Life form?	Large shrub to tree (Carr); other.	L	MH
Allelopathic properties?	Has been shown to have allelopathic properties under experimental conditions, inhibiting germination in some species and reducing growth in others. It is not known to what extent it impacts upon other species in natural habitats (Florentine & Westbrooke 2003).	M	H
Tolerates herb pressure?	Toxic, avoided by stock, under permanent grazing it can establish, under more intense rotational grazing establishment can be prevented. Pademelons can limit seedlings and prevent the plant reaching maturity. Mature plants have been killed by mountain possums, however they also removed the bark (Van Dyck 1979). A number of biocontrol agents have been released in Sth Africa, no such projects reported in Australia.	MH	MH
Normal growth rate?	Grows rapidly in the first year reaching maturity (Blood 2001).	H	MH
Stress tolerance to frost, drought, w/logg, sal. etc?	Fire kills mature plants but stimulates germination of seedlings, plants may also coppice from underground stems (Blood 2001; Symon 1981). Tolerant of moderate frost (to -5) (Blood 2001). Tolerant of moderate drought once established (Blood 2001). Able to grow in coastal areas therefore may have a tolerance to salinity. Unknown tolerance to waterlogging.	MH	MH
Reproduction
Reproductive system	It can coppice and regrow from the stump or underground stems if damaged, however its primary mode of reproduction and dispersal is through seed containing fruits (Blood 2001).	ML	MH
Number of propagules produced?	Up to 20,000 seeds per tree (Florentine & Westbrooke 2003). Each fruit contains 150-250 seeds, each plant produces more than 8-14 fruit therefore a plant is capable of producing more than 2000 seeds per year (Symon 1981).	H	H
Propagule longevity?	Seed viability has been reported as greater than 39 years (Enright & Cameron 1988). If left on the soil surface, viability may be reduced by 90% within 2 years, however when buried to 15 cm viability only reduced by 4% (Campbell & Van Staden 1994).	H	H
Reproductive period?	Short lived shrub, 10-15. Can reach maturity within first year therefore capable of more than 10 years reproduction (Blood 2001).	H	MH
Time to reproductive maturity?	Fast growing species, Can reach maturity within one year (Blood 2001).	H	MH
Dispersal
Number of mechanisms?	Spread by water birds and internally by animals (Blood 2001).	H	MH
How far do they disperse?	Satin Bowerbird has been observed eating the fruits of this species and the Satin bowerbird has been reported to be capable of dispersing olive seeds 1 km by regurgitation (Spennemann & Allen 2000; Stansbury & Vivian-Smith 2003). As this species seeds are much smaller than olives (<2 mm), dispersal by excretion may distribute them further than 1 km.	H	H

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