Invasiveness Assessment - Pale-berry asparagus fern (Asparagus declinatus) 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 Pale-berry asparagus fern

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: Pale-berry asparagus fern
Scientific name: Asparagus declinatus

Question	Comments	Rating	Confidence
Establishment
Germination requirements?	The above ground shoots act as annuals, emerging in autumn from rhizomes, to then senesce with increasing temperatures from November to January (Lawrie 2006a). Germination can occur during the cooler months from March to August (Dept. Water, Land & Biodiversity Conservation 2006). Therefore germination is restricted by seasonal conditions.	MH	MH
Establishment requirements?	In Australia, has been found in low open forest (Bass & Lawrie 2003). Under experimental conditions it has been reported to grow well under 70-90% shade and open sun (Bass et al 2006). The species has not been reported to establish under such conditions and therefore its known establishment under moderate canopy conditions is all that can be gone by at this stage.	MH	MH
How much disturbance is required?	In South Africa, ‘found in fybros or coastal scrub, predominantly on rocky outcrops’ (Obermeyer 1984 cited in Bass & Lawrie 2003).‘Potential to inhabit a range of vegetation communities including closed forests and open woodlands’ (Lethbridge 2005). In Australia, has been found in low open forest (Bass & Lawrie 2003). Can establish in healthy natural ecosystems.	H	MH
Growth/Competitive
Life form?	Climbing perennial. Geophyte (Bass & Lawrie 2003).	ML	MH
Allelopathic properties?	None described.	L	M
Tolerates herb pressure?	Grazing by sheep and cattle has been tried as a control method, however it is not preferred by either species, sheep mainly eating the new shoots, at high stocking rates can reduce the plant and restrict flowering and therefore sexual reproduction (Lawrie 2006b). In summer the species is not preferred and high stocking rates are required to prevent sexual reproduction.	MH	H
Normal growth rate?	There little is known about the growth rate of this species, however for management purposes it is presumed to be similar to A. asparagoides (Dept. Water, Land & Biodiversity Conservation 2006).	M	L
Stress tolerance to frost, drought, w/logg, sal. etc?	Drought tolerant, the species senesces during the summer months to regrow from rhizomes in autumn (Lawrie 2006a). A. asparagoides ‘is frost tolerant and its root system allows it to survive summer droughts’ (Weeds CRC 2003). Fire is still being experimented with as a control method, however at this stage it has been unsuccessful due to the difficulty of maintaining a high intensity fire so as to cook the tubers (Lawrie 2006b). Susceptible to waterlogging. Found along coast (Lawrie 2006a ). Therefore likely to be salt tolerant.	MH	MH
Reproduction
Reproductive system	Capable of both sexual and vegetative reproduction, by flowering and producing fruit and having an extensive branching rhizomatous root system (Lawrie 2006a).	H	H
Number of propagules produced?	Normally have 5-8 seeds per fruit but can range from 2-14, fruit production can vary from 100-800 fruit m^-2 therefore average seed production can be 4,800 seeds m^-2 (Lawrie 2006a). This species can form extensive root systems of branching rhizomes, with many of the rhizomes producing tubers and shoots (Lawrie 2006a). Therefore multiple stems may be considered the same plant and therefore it is possible that the number of propagules produced by one plant exceeds 2,000.	H	MH
Propagule longevity?	For A. asparagoides ‘buried seed .. rots within two years, while seed on the soil surface may be viable for at least three years’ (Weeds CRC 2003). Studies currently being done to determine propagule longevity for A. declinatus.	M	L
Reproductive period?	Insufficient information to determine reproductive period for A. declinatus.	M	L
Time to reproductive maturity?	Unknown, A. asparagoides takes three years to flower, vegetative reproduction may occur faster.	M	L
Dispersal
Number of mechanisms?	A. declinatus seeds may be dispersed by the grey currawong, Australian magpie, Australian raven, brush wattlebird and red wattlebird (Bass & Lawrie 2003; Lawrie 2006a). Mammal species are also reported as dispersal agents, including brush tailed and ring tailed possums, foxes and bush rats (Bass 2002; Lawrie 2006). Bird dispersed and eaten by highly mobile animals.	H	H
How far do they disperse?	Dispersal varies with the species between <100 m for the smaller bird species to 10 km for the currawong (Lawrie 2006a). The dispersal range of various species has been reported as follows; the grey currawong , 20 km, the Australian magpie 1 km and fox, 5 km (Spennemann & Allen 2000).	H	H

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