Invasiveness Assessment - Praxelis (Praxelis clematidea) 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 Praxelis.

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)
To view the information PDF requires the use of a PDF reader. This can be installed for free from the Adobe website (external link).

Common Name: Praxelis
Scientific name: Praxelis clematidea

Question
Comments
Rating
Confidence

Establishment

Germination requirements? “Most germination occurs following rainfall, but it can occur year round under suitable conditions (e.g. in gardens, irrigated pasture)” (CRC Weed Management, 2003).
H
M

Establishment requirements? “Able to invade the understorey of relatively undisturbed woodlands” (Waterhouse, 2003). Tolerates part shade to full sun but does not cope well under heavy shade (CRC Weed Management, 2003). Can establish under moderate canopy cover.
MH
H

How much disturbance is required? “Able to invade the understorey of relatively undisturbed woodlands.” Also invades roadsides,
streambanks, pastures, sugarcane etc., (Waterhouse, 2003).
MH
H

Growth/Competitive

Life form? “Annual or short-lived perennial herb” (Waterhouse, 2003).
L
H

Allelopathic properties? None found.
L
L

Tolerates herb pressure? “Not eaten by stock” (Pollock et al, 2004)
H
MH

Normal growth rate? “It can grow up to c. 1.2 m tall but most plants are c. 40-80 cm” (Csurhes, 1998), which is an average height for an annual or short-lived perennial.
MH
MH

Stress tolerance to frost, drought, w/logg, sal. etc? Frost resistance (Waterhouse, 2003). Rapidly colonises bare earth after fire (CRC Weed Management, 2003) although this is probably by seed. “Woody rhizome protects from fire” (anon, 2004). Not noted as growing in permanently wet conditions, although it does “grow vigorously along riverbanks” which is the type of environment it would likely be found in “areas where annual rainfall is less than 500 mm” (CRC Weed Management, 2003), suggesting low drought tolerance. Exhibits some frost and fire resistance, but not waterlogging or drought.
ML
M

Reproduction

Reproductive system “Mainly spreads by seeds…Roots and new plantlets form along branches in contact with soil” (CRC Weed Management, 2003).
H
M

Number of propagules produced? “Can produce large numbers of seeds.” Each inflorescence has 30 - 50 florets. Sixteen florets appear on one stem, with 5 flowering stems on one plant, as pictured in CRC Weed Management (2003). 50 x 16 x 5 = 4,000.
H
M

Propagule longevity? No data found
M
L

Reproductive period? “Forms monospecific stands, excluding other vegetation (PIER, 2005).
H
MH

Time to reproductive maturity? Already flowering in its first season (Veldkamp, 1999).
H
H

Dispersal

Number of mechanisms? Airborne seed dispersal seems to be effective over short distances (Waterhouse, 2003). Pappus assists dispersal also by water, or by attaching to fur or feathers (CRC Weed Management, 2003).
MH
MH

How far do they disperse? As this plant “grows vigorously along riverbanks” and its seed can be dispersed by water (CRC Weed Management, 2003), many propagules would be likely to reach 200-1,000 m but few will disperse greater than 1 km. “Airborne seed dispersal seems to be effective over short distances” (Waterhouse, 2003).
MH
MH

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Question	Comments	Rating	Confidence
Establishment
Germination requirements?	“Most germination occurs following rainfall, but it can occur year round under suitable conditions (e.g. in gardens, irrigated pasture)” (CRC Weed Management, 2003).	H	M
Establishment requirements?	“Able to invade the understorey of relatively undisturbed woodlands” (Waterhouse, 2003). Tolerates part shade to full sun but does not cope well under heavy shade (CRC Weed Management, 2003). Can establish under moderate canopy cover.	MH	H
How much disturbance is required?	“Able to invade the understorey of relatively undisturbed woodlands.” Also invades roadsides, streambanks, pastures, sugarcane etc., (Waterhouse, 2003).	MH	H
Growth/Competitive
Life form?	“Annual or short-lived perennial herb” (Waterhouse, 2003).	L	H
Allelopathic properties?	None found.	L	L
Tolerates herb pressure?	“Not eaten by stock” (Pollock et al, 2004)	H	MH
Normal growth rate?	“It can grow up to c. 1.2 m tall but most plants are c. 40-80 cm” (Csurhes, 1998), which is an average height for an annual or short-lived perennial.	MH	MH
Stress tolerance to frost, drought, w/logg, sal. etc?	Frost resistance (Waterhouse, 2003). Rapidly colonises bare earth after fire (CRC Weed Management, 2003) although this is probably by seed. “Woody rhizome protects from fire” (anon, 2004). Not noted as growing in permanently wet conditions, although it does “grow vigorously along riverbanks” which is the type of environment it would likely be found in “areas where annual rainfall is less than 500 mm” (CRC Weed Management, 2003), suggesting low drought tolerance. Exhibits some frost and fire resistance, but not waterlogging or drought.	ML	M
Reproduction
Reproductive system	“Mainly spreads by seeds…Roots and new plantlets form along branches in contact with soil” (CRC Weed Management, 2003).	H	M
Number of propagules produced?	“Can produce large numbers of seeds.” Each inflorescence has 30 - 50 florets. Sixteen florets appear on one stem, with 5 flowering stems on one plant, as pictured in CRC Weed Management (2003). 50 x 16 x 5 = 4,000.	H	M
Propagule longevity?	No data found	M	L
Reproductive period?	“Forms monospecific stands, excluding other vegetation (PIER, 2005).	H	MH
Time to reproductive maturity?	Already flowering in its first season (Veldkamp, 1999).	H	H
Dispersal
Number of mechanisms?	Airborne seed dispersal seems to be effective over short distances (Waterhouse, 2003). Pappus assists dispersal also by water, or by attaching to fur or feathers (CRC Weed Management, 2003).	MH	MH
How far do they disperse?	As this plant “grows vigorously along riverbanks” and its seed can be dispersed by water (CRC Weed Management, 2003), many propagules would be likely to reach 200-1,000 m but few will disperse greater than 1 km. “Airborne seed dispersal seems to be effective over short distances” (Waterhouse, 2003).	MH	MH