Invasiveness Assessment - Camel thorn (Alhagi maurorum) 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 Camel thorn.

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: Camel thorn
Scientific name: Alhagi maurorum

Question	Comments	Reference	Rating
Establishment
Germination requirements?	“Seeds germinate in spring. Aerial growth dies in autumn and new shoots emerge from roots each spring.” “Seeds appear to need special conditions for germination, for example, in North America, seedlings are usually found only in bovine dung suggesting that scarification of the seed coat…may be necessary.” Established plants re-shoot from roots each spring. Requires natural seasonal disturbance for germination or root development.	Parsons & Cuthbertson (2001)	MH
Establishment requirements?	“Seeds appear to need special conditions for germination.” It is found mostly in pastures and neglected areas and, in the northern parts of Victoria, is usually associated with irrigation. It is not documented to occur in undisturbed natural ecosystems, however, in the United States it is known to be abundant along riverbanks, canals and irrigation ditches.	Parsons & Cuthbertson (2001)	M
How much disturbance is required?	“Camelthorn has become a troublesome weed overseas in cereal and horticultural crops where repeated cultivation aids its spread.” Most commonly occurs in highly disturbed or neglected environments.	Parsons & Cuthbertson (2001)	ML
Growth/Competitive
Life form?	“An erect perennial shrub.” A member of the Fabaceae family (legume).	Parsons & Cuthbertson (2001)	MH
Allelopathic properties?	None documented.		L
Tolerates herb pressure?	“Camelthorn is grazed…by cattle and sheep in the United States and Australia.” Consumed, but root system remains intact to produce new shoots.	Parsons & Cuthbertson (2001)	ML
Normal growth rate?	“Seeds germinate in spring and rapid root growth ensures establishment ahead of most other species.” Rapid growth rate is likely to exceed most other species of same life form.	Parsons & Cuthbertson (2001)	H
Stress tolerance to frost, drought, w/logg, sal. etc?	“Plants are sensitive to low temperatures.” Will not withstand flooding for extended period (weeks). While there is no documented evidence of the plant’s ability to survive drought, its deep root system may ensure the plant endures through periods of drought.	Parsons & Cuthbertson (2001)	ML
Reproduction
Reproductive system	Reproduces vegetatively and sexually.	Parsons & Cuthbertson (2001)	H
Number of propagules produced?	In the United States, “Flower production is high under hot, dry conditions (700–4,000 per plant). There are 5 to 8 seeds in the pod.” Plants could produce more than 2,000 seeds annually.	SWEPIC	H
Propagule longevity?	“Seed viability in semi-arid soils may extend over a number of years.” “Seeds remain viable for many years.” >25% of seed survive 5–10 years. include other propagule material e.g. roots increase from ML to MH.	SWEPIC Parsons & Cuthbertson (2001)	MH
Reproductive period?	A perennial shrub with an extensive and vigorous root system. “It is strongly competitive with other plants and, in the Merbein infestation, has eliminated most other vegetation.” Long-lived, by does not establish as a monoculture.	Parsons & Cuthbertson (2001)	MH
Time to reproductive maturity?	“Plants generally do not flower until they are 1 year old.” Propagules produced after 1 year.	Parsons & Cuthbertson (2001)	MH
Dispersal
Number of mechanisms?	“Camelthorn is grazed…cattle and sheep in the United States and Australia.” Cultivation equipment can also spread root fragments.	Parsons & Cuthbertson (2001)	MH
How far do they disperse?	Cattle and sheep graze the plant, and machinery may spread propagules. These vectors could spread the plant by more than 200 metres from infestation.	Parsons & Cuthbertson (2001)	MH

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