Invasiveness Assessment - Serrated tussock (Nassella trichotoma) 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 Serrated tussock.

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: Serrated tussock
Scientific name: Nassella trichotoma

Question	Comments	Reference	Rating
Establishment
Germination requirements?	“Seeds germinate at any time of the year but mostly in autumn and winter”.	P & C (1992 p. 112)	H
Establishment requirements?	“Occurring as a weed in open pastures and lightly timbered areas”.	P & C (1992 p. 112)	MH
How much disturbance is required?	“Invades nature grasslands, grassy woodlands, drier forests and rocky shrublands”.	Muyt (2001 p. 75)	MH
Growth/Competitive
Life form?	Perennial tussock-forming grass.	P & C (1992 p. 112)	MH
Allelopathic properties?	No Allelopathic properties described.		L
Tolerates herb pressure?	“The plant is eaten by sheep and cattle only if nothing else is available”.	P & C (1992 p. 113)	H
Normal growth rate?	“Most seedlings that establish in a dense strand of N. trichotoma or in a vigorous improved pasture are killed by competition in the first or second spring or summer”. Seedlings not killed by competition will grow as fast as comparable grasses in the surrounds.	Campbell & Vere (1995 p. 194)	MH
Stress tolerance to frost, drought, w/logg, sal. etc?	“Tolerates, fire, drought and frost”.	Blood (2001 p. 208)	MH
Reproduction
Reproductive system	“Reproduction is by seed”.	P & C (1992 p. 112)	ML
Number of propagules produced?	“Seed production is prolific and a hectare of dense tussock growth is estimated to produce more that 2 tonnes of seed per year”. “Large vigorous plants can produce 100,000 seeds annually”. (Muyt 2001 p. 75)	P & C (1992 p. 114)	H
Propagule longevity?	“Some seeds remain dormant in the soil for up to 15 years, possibly more”. “Soil in a forest that had no fresh seed added for 13 years had a germination capacity of 8%”. (Campbell & Vere 1995 p. 194).	P & C (1992 p. 114)	ML
Reproductive period?	“Tussocks persist for many years producing new flowering stems and some new leaves each year”.	P & C (1992 p. 113)	MH
Time to reproductive maturity?	“Plants rarely flower in the first year but continue vegetative growth until the second summer when flowers and seeds are usually produced”.	P & C (1992 p. 112)	MH
Dispersal
Number of mechanisms?	See ‘dispersal’ section.	P & C (1992 p. 113)	MH
How far do they disperse?	“The seed head breaks off near the base of the plant and may be blown considerable distances, even up to several kilometres”.	P & C (1992 p. 113)	H

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