Invasiveness Assessment - Sallow wattle (Acacia longifolia) 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 Sallow wattle.

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 - 1 MB)
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Common Name: Sallow wattle
Scientific Name: Acacia longifolia

Question	Comments	Rating	Confidence
Establishment
Germination requirements?	Disturbance around infestations usually stimulates mass germination of A. longifolia seeds. Stimulated to germinate by fire (Pieterse and Cairns 1986). Although extensive growth occurs in areas where fire has not occurred for many years (Cavanagh and Tran 1980). About 10% of fresh seeds germinate each year without any disturbance (Muyt 2001).	MH	MH
Establishment requirements?	Grows in partial shade to full sun and will tolerate a wide range of soil types, exposed positions and seasonal dry spells and occurs generally in areas receiving more than 550 mm annual rainfall. (Muyt 2001). Their ability to fix nitrogen has enabled them to invade nutrient-poor environments (Marchante et al. 2004). Can establish under moderate canopy cover.	MH	MH
How much disturbance is required?	Occurs within heathlands, woodlands and forests (Muyt 2001), also occurring riparian habitats, grassland, coastal dunes and scrub (Weber 2003), sclerophyll communities and coastal heath and scrub (Harden 2002).	H	MH
Growth/Competitive
Life form?	Upright spreading bushy shrubs to small trees; 1-8 m (Costermans 1983), which may produce dense thickets (Weber 2003).	L	H
Allelopathic properties?	Described as not having any allelopathic properties (PIER 2007).	L	M
Tolerates herb pressure?	Unknown: No information was found to document that A. longifolia can or cannot tolerate herbivory pressure and produce propagules.	M	L
Normal growth rate?	A. longifolia is described as a rapidly growing shrub (Marchante et al. 2004), may equal competitive species of the same life form.	MH	MH
Stress tolerance to frost, drought, w/logg, sal. etc?	Tolerates seasonal dry spells (Muyt 2001) and described as being drought resistant (Garden California 1997). Disturbance by fire stimulates mass germination, causing extensive growth (Pieterse and Cairns 1986). Tolerant to drought and fire, no information suggests tolerance to frost, waterlogging or salinity although maybe tolerant.	MH	M
Reproduction
Reproductive system	Sexual reproduction occurs (Muyt 2001), self and cross pollination.	ML	MH
Number of propagules produced?	A. longifolia produces huge amounts of seeds annually as many as 11,500 seeds have been recorded (Pieterse 1987). Number of propagules produced per flowering event therefore maybe greater than 2000.	H	H
Propagule longevity?	Long lived seeds are regarded as being paramount for the invasiveness of the plant (Pieterse, 1986 in Dennill and Donnelly 1991). Seeds may remain dormant for well over a decade (Muyt 2001).	MH	MH
Reproductive period?	While A. longifolia may survive for over 50 years in its natural range, those in other areas commonly die within 25 years (Muyt 2001). Pieterse and Cairns (1988) describe A. longifolia forming dense monocultures.	H	H
Time to reproductive maturity?	Plants reach sexual maturity within two to three years (Muyt 2001).	ML	MH
Dispersal
Number of mechanisms?	Seed is dispersed by birds, ants, slashing, in soil and garden refuse (Muyt 2001). Also noted by PIER (2007) that propagules are dispersed by water.	H	MH
How far do they disperse?	Due to seeds being able to disperse by birds (Muyt 2001) and water (PIER 2007), it can be concluded that propagules will disperse greater than one kilometre.	H	MH

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