Invasiveness Assessment - Bridal creeper (Western Cape form) (Asparagus asparagoides) in Victoria (nox)

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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 Bridal creeper (Western Cape form).

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: Bridal Creeper (Western Cape form)
Scientific name: Asparagus asparagoides

Question	Comments	Rating	Confidence
Establishment
Germination requirements?	“Seedlings usually emerge in autumn” … initial growth is not dependent on any seasonal rainfall triggers. (Muyt , 2001) “Seeds germinate in autumn or early winter” (Ibid.). Initial vegetative growth from tubers is rapid, independent of external stimulation, and is dependent only on the stored reserves of moisture and energy (Cooke and Robertson, ’90) Seeds germinated at various temperatures (10⁰– 23⁰C) (Ibid.). Opportunistic germinator, can germinate at any time whenever water is available.	H	H
Establishment requirements?	“Tolerates shade or part shade” (Blood, ’01). Bridal creeper occurs primarily in dappled shade, or at the edges of dense shade … in [full] shade situations long prostrate stems are produced [that] produce little, or no, fruit (Kleinjan & Edwards, ’99). Can establish under moderate canopy or litter.	MH	H
How much disturbance is required?	Occurs in undisturbed vegetation e.g. heathland and Mallee shrubland (Carr et al., ‘92). “It invades disturbed and undisturbed vegetation across a wide range of habitats” (Raymond, ‘96). Establishes in healthy AND undisturbed natural ecosystems.	H	MH
Growth/Competitive
Life form?	Perennial climber that dominates ground flora, and can form “dense curtains smothering shrubs and the lower canopy of trees” (Muyt, ’01). Shoots grow upright to twine amongst nearby trees, shrubs, and smother other supports. (NAWMC, ’06) Most reliable way to distinguish between the A. asparagoides (common form) and the WCF is to dig up and compare the tubers of mature plants. (NAWMC, ’06) Climber.	ML	MH
Allelopathic properties?	None found described in literature reviewed.	M	L
Tolerates herb pressure?	“…During … flowering season … large numbers of buds were recorded, but very few flowers or fruits were produced, possibly due to extensive herbivore damage … noted at the time... (Kleinjan & Edwards, ’99). Extensive herbivore damage to the foliage can significantly reduce fruiting (Ibid.). Herbivory by the bridal creeper leafhopper (Zygina spp.) is a permitted means of biocontrol for A. asparagoides (common form), WCF has been observed to be damaged by such herbivory (the extent to the damage is as yet unclear) (NAWMC, ’06). Bridal creeper is a palatable specimen and is not an agricultural weed due to grazing by stock (Carr, ‘96). Consumed and recovers slowly. Reproduction strongly inhibited by herbivory but still capable of vegetative propagules production (tubers); weed may still persist. NB. It is noteworthy that the common form of A. asparagoides is currently under a successful biocontrol program with the rust fungus Puccinia myrsiplylli. In current trials WCF has shown itself to be resistant to this biocontrol agent. Tubers of WCF found growing well on soil surface where previous rust release on common form; when dug down approx. 10 cm below WCF tubers, found recently deceased common form tubers. Whether this indicates WCF out-competing common form, reinfesting areas of dead common form (through biocontrol action, or other means of local eradication) it is too early to assess (Hay, ’07).	ML	H
Normal growth rate?	Initial shoot growth is rapid to out compete plants of a similar habit (NAWMC, ’06), however, its growth rate appears slower than the common form of A. asparagoides (Holland Clift, ’05). Maximum growth rate less than many species of the same life form.	ML	MH
Stress tolerance to frost, drought, w/logg, sal. etc?	Bridal creeper is common in coastal zones … occurs primarily in dappled shade, or at the edges of dense shade (NB in full shade long prostrate stems are produced [that] produce little, or no, fruit. … along the banks of estuaries (Kleinjan & Edwards, ’99). Although spp. reportedly not found in very saline conditions, it has been found thriving on sand dunes adjacent to South Australian beaches (Hay, ’07). Grows in shady, moist conditions. (NAWMC, ’06). The tubers provide and store water, energy, and nutrient that enable the plant to survive over summer [dry periods] (Ibid.). Bridal creeper tolerates drought conditions via dormant rhizomes and tubers (Muyt, ’01). Highly tolerant of salinity, waterlogging, drought; tolerant of shade.	MH	H
Reproduction
Reproductive system	“Reproduces by seed and rhizomes. (Muyt, ’01). Bridal creeper can regrow from rhizome fragments (Cooke & Robertson, ’90). Bridal creeper is self-fertile (NAWMC, ’06). Both vegetative and sexual reproduction.	H	MH
Number of propagules produced?	“Plants produce hundreds of fruits annually, each containing up to nine seeds. Seed viability approaches 90% (Muyt, ’01). Fruit production may exceed 1,000 berries/m² (NAWMC, ’06). Greater than 2,000.	H	MH
Propagule longevity?	Bridal creeper has a relatively short-lived seed bank of several years (NAWMC, ’06). Bridal creeper can regrow from rhizome fragments (Cooke & Robertson, ’90). The rhizomes remain viable (although they may lie dormant) as long as they contain moisture and with a growing apex (Ibid.), therefore it has viable propagules for the life of the plant. Vegetative propagules may survive for greater than five years, at present they are known to survive at least five years from experimental work of five years’ duration, this is still on-going, thus the longevity is still unknown. Vegetative propagules, and > 25% of seeds, may survive 5 – 10 years.	ML	MH
Reproductive period?	Unknown from literature reviewed.	M	L
Time to reproductive maturity?	Three years from germination before flowering (NAWMC, ’06). Seedlings develop their first tubers within ten weeks (Muyt, ’01). Produces vegetative propagules that have the capacity to form separate individuals in under a year.	H	MH
Dispersal
Number of mechanisms?	Viable seeds spread in emu scats (Cooke & Robertson, ’90; NAWMC, ’06) main vectors are birds, foxes and possibly rabbits (Ibid.). Dumping of garden waste, trading / sharing of plants by gardeners (Ibid.) and road making (Cooke and Robertson, ‘90) are the main sources of vegetative spread. Edible fruit dispersed by highly mobile animals (birds, foxes).	H	MH
How far do they disperse?	“Most seed dispersal events are restricted to < 100 metres … [but] … rare long distance dispersals, up to several kilometres, have been reported (Stansbury, ’01) …” (NAWMC, ’06). Likely that at least one propagule will disperse greater than one kilometre.	H	MH

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