Invasiveness Assessment - Karamu (Coprosma robusta) 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 Karamu.

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: Karamu
Scientific name: Coprosma robusta

Question	Comments	Rating	Confidence
Establishment
Germination requirements?	‘…germination was greater after 4 weeks or more of stratification (Mackay et al 2002)’. Appears to require natural seasonal disturbances, e.g. cooler winter temperatures, for germination.	MH	MH
Establishment requirements?	Invades damp and wet sclerophyll forest (Carr et al 1992). ‘It tolerates full sun or shade equally well (TFS 2007)’. Known as an understorey species in Pinus radiata stands in NZ (Ogden et al 1997). Can establish under a moderate canopy.	MH	MH
How much disturbance is required?	‘Able to invade relatively undisturbed sites (Blood 2001)’.	H	MH
Growth/Competitive
Life form?	Large shrub or small tree to 6 m (Blood 2001).	L	MH
Allelopathic properties?	No allelopathic properties described for C. robusta or similar species C. repens, of which the literature is more extensive.	L	M
Tolerates herb pressure?	‘Plants are tolerant of heavy clipping or pruning (PFF 2002)’. Moderately tolerant of animal browsing (NZERN 2002). ‘Plants (C. repens) can re-shoot vigorously from the base if top growth is damaged or removed (Muyt 2001)’. Information suggests it would recover quickly from herbivory.	MH	M
Normal growth rate?	‘Fast growing and inclined to become weedy (NZPCN 2005)’. Due to its rapid growth, in New Zealand it is often planted on bare infertile sites where it provides shelter for subsequent plantings (TFS 2007). Williams & Buxton (1989) found it to have one of the highest relative growth rates within a group of tree and shrub species studied. Rapid growth that will exceed most other species of the same life form.	H	MH
Stress tolerance to frost, drought, w/logg, sal. etc?	Described as sensitive to drought (Bannister 1986) but also as having medium drought tolerance (NZERN 2002). Occurs in rivers subject to tidal affects and ‘it has no trouble coping with inundation or brackish water (A. Crane pers. com)’. Often found where soil is poor or swampy, or where conditions are windy or cold, it is a tough plant that will grow in difficult conditions…wind hardy and frost tolerant when mature (TFS 2007)’. Similar species C. repens is tolerant to fire (Blood 2001). Displays tolerance to frost, water-logging, salinity and maybe fire.	MH	M
Reproduction
Reproductive system	‘Reproduces by seed (Blood 2001)’. ‘Plants are considered not self-fertile (PFF 2002)’, however, apomictic seed formation (without sexual reproduction) is observed in natural populations (Heenan et al 2003).	ML	MH
Number of propagules produced?	‘Heavily fruiting females can be very spectacular (NZPCN 2005)’. Produces 4 seeds per fruit (Williams et al. 2000). Images indicate that an individual plant could produce many more than 500 fruits.	H	M
Propagule longevity?	Burrows (1995) says that there is no indication that C. robusta forms ‘soil seed banks which would last for more than the period from seed-shed to the following spring’ and suggests that the dense stands ‘which spring up after forest disturbance do so from the seed crop of the previous fruiting season’. Seeds survive less than 5 years.	L	H
Reproductive period?	As a large shrub / small tree (Blood 2001), likely to produce propagules for >10 yrs. Forms dense thickets / monocultures (R. Adair pers. com., J. Lynch pers. com).	H	M
Time to reproductive maturity?	‘Karamu does not produce fruit until about 3 years after planting (TFS 2007)’. Takes 2-5 years to reach sexual maturity.	ML	ML
Dispersal
Number of mechanisms?	Spread by birds and other animals and dumped garden waste (Blood 2001).	H	MH
How far do they disperse?	‘Seedlings have been found germinating in gullies and bushland several kilometres from older infestations (Pers. com. J. Lynch). Birds and other animals (Blood 2001) could disperse seed greater than 1 km.	H	M

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