Invasiveness Assessment - Bent grass (Agrostis capillaris L., Agrostis castellana) 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 Bent grass.

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: Bent grass
Scientific name: Agrostis capillaris L., Agrostis castellana

* Refer to ‘Note’ at end of document acknowledging confusing species identification and nomenclature.

Question	Comments	Rating	Confidence
Establishment
Germination requirements?	In the field, seeds germinate in autumn and spring (HDRA 2006). Requires natural seasonal disturbances for germination.	MH	MH
Establishment requirements?	Described growing in shaded situations (Dore & McNeil 1980) and as invading forest (Carr et al 1992). Could establish under a moderate canopy.	MH	MH
How much disturbance is required?	It is described as being one of worst pasture weeds of the high rainfall zone of Victoria dominating in lightly grazed pastures (Hill et al 1996), suggesting it can establish with minimum disturbance such as in well established pasture. Also described as invading grassland (Edgar & Connor 2000), grassy woodland, sclerophyll forest/woodland, heathland & heathy woodland, riparian and alpine & subalpine vegetation (Carr et al 1992). Establishes in relatively intact natural ecosystems.	MH	MH
Growth/Competitive
Life form?	Life form: Grass (Batson 1998).	MH	H
Allelopathic properties?	No evidence was found to suggest the presence of allelopathy within the species, or genus.	L	M
Tolerates herb pressure?	Under severe grazing, common bent will soon appear in grassland and within 5 years it can make up a significant proportion of the sward (Spedding 1966). Adapts to heavy grazing by growing close to ground level. Bent grass grows slowly over winter/ early spring producing little feed for stock, but in late spring/early summer bent grass produces excess feed of poor quality which is not utilised by stock (Batson 1998b). Appears to be only preferred and grazed for part of the year.	MH	MH
Normal growth rate?	A. castellana grows more vigorously by rhizomes than A. capillaris (Batson 1998) and is more competitive and chokes out ryegrass and clover (Batson 1998b). Grows slowly over cooler periods but in late spring and early summer produces excess feed (Batson 1998b). Although slow growing in Winter, the literature suggests overall growth would equal competitive species of the same life form.	MH	MH
Stress tolerance to frost, drought, w/logg, sal. etc?	Described as surviving waterlogged soils better than ryegrass and clover (Batson 1998b), dominating seasonally flooded grasslands (Sanchez & Peco 2004) and occurring in seasonal wetlands (Carr et al 1992). Hardy to European winters (Jones & Charles 1984) and occurs on subantarctic Islands (Clayton et al 2007). Not tolerant of salinity (Marcum 2004). Exhibits some tolerance to burning (HDRA 2006) probably due to rhizome system. Likely to have some drought tolerance occurring in semi-arid grasslands (Vaquero et al 2003).	MH	MH
Reproduction
Reproductive system	Reproduces sexually by seed (Hill et al 1996) and vegetatively via rhizomes (Batson 1998).	H	H
Number of propagules produced?	Observed producing up to 298,000 seeds/m² (Alexander 1995 in Batson 1999). It is likely that an individual plant would produce greater than 2,000 seeds.	H	M
Propagule longevity?	‘Thompson et al. (1993) suggest that based on seed character, common bent seed is likely to persist for longer than 5 years. Seed buried at 13 cm depth retained 28 % viability after 4 years (Lewis 1973 in HDRA 2006)’. Greater than 25% of seed may survive beyond 5 years	ML	M
Reproductive period?	A perennial grass (Edgar & Forde 1991), therefore having the potential to produce propagules for several (3+) years.	MH	MH
Time to reproductive maturity?	As a grass (Batson 1998), time to reproductive maturity is presumed to be less than 2 years.	MH	MH
Dispersal
Number of mechanisms?	Spread by wind and attachment to animals (Carr et al 1992). Some seeds also likely to be accidentally ingested and dispersed internally by grazers (Janzen 1984).	MH	MH
How far do they disperse?	Attachment and internal dispersal can spread seeds considerable distance (Janzen 1984), with free ranging introduced and native grazers able to disperse seeds greater than 1 km.	H	MH

Note: Literature relevant to both A. castellana Boiss. & Reuter and A. capillaris has been used to complete this assessment. This is due to the considerable debate about the identity of the most common bent grass species that exists in Victoria. There is debate about the presence or otherwise of A. castellana in Victoria (not listed in the current ‘Census of the Vascular Plants of Victoria (Walsh & Stajsic 2007)’). Some authors consider it to be present (Batson 1998, Hill et al 1996), others acknowledge A. capillaris and/or two varieties of this species (Walsh & Entwisle 1994). It is also recognised that introgression and hydridisation readily occur between A. capillaris and A. castellana (Pers. Com. N. Walsh & A. Brown). In addition, the two species are documented as being similar (Hafliger & Scholz 1982).

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