Invasiveness Assessment - Lippia (Phyla canescens) 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 Lippia.

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: Lippia
Scientific name: Phyla canescens

Question	Comments	Rating	Confidence
Establishment
Germination requirements?	‘In southern NSW lippias ability to grow and spread is mainly limited to the period October to April (Dellow et al 2001)’. The remarkable ability of Lippia to reinvade from seeds and cuttings means it can quickly regenerate, particularly following significant rain or flooding (Dellow et al 2001). Appears to require natural seasonal disturbances for germination.	MH	MH
Establishment requirements?	Being a C3 plant, it is able to tolerate shady conditions and has therefore been recommended as a lawn and garden plant, particularly for shady conditions (Leigh & Walton 2004). Can establish under a moderate canopy.	MH	MH
How much disturbance is required?	‘Lippia is considered a major threat to riparian and associated ecosystems because of its dominance over native plants. Forms monocultures on otherwise undisturbed land (Julien et al 2004)’. Establishes in relatively intact ecosystems, e.g. riparian communities, wetlands.	MH	MH
Growth/Competitive
Life form?	Creeper: Prostrate perennial herb with extensive fibrous roots and creeping stems (Julien et al 2004).	ML	MH
Allelopathic properties?	Studies show that plant extracts significantly reduce the germination of some species including lettuce, vetch and clover (Elakovich & Stevens 1985, Daley et al 2005). Allelopathic properties seriously affecting some plants.	MH	H
Tolerates herb pressure?	Relatively unpalatable to cattle as they tend to only eat small amounts of the plant and only after other pasture species are exhausted (Lucy et al 1995). Consumed but not preferred.	MH	MH
Normal growth rate?	Lippia is a fast growing plant and when in competition with other species, it can grow to a height of 20-30 cm, and dominate other plants (Leigh & Walton 2004). Rapid growth rate.	H	MH
Stress tolerance to frost, drought, w/logg, sal. etc?	Drought resistant (Julien et al 2004) and able to tolerate long periods of water logging (Leigh & Walton 2004). It is documented as being salt tolerant and as growing at sites of heavy winter frost (Richardson 1994 in Leigh & Walton 2004) and is reported to be tolerant of fire (Earl 2003). Its deep taproot allows it to go into dormancy during periods of stress, and then quickly re-grow after rainfall or flooding (Lucy et al 1995).	H	MH
Reproduction
Reproductive system	Reproduces sexually and vegetatively by producing roots at stem nodes (Mawhinney 2004).	H	H
Number of propagules produced?	Described as being a prolific seeder (Lucy et al 1995), but also, that seed set may be low in Australia due to the discovery of very small seed banks (Leigh & Walton 2004). However, no information on the number of propagules produced by an individual plant was found.	M	ML
Propagule longevity?	‘There is no information in the literature on how long seed may remain viable in the soil (Lucy et al 1995)’.	M	L
Reproductive period?	It forms monocultures (Julien et al 2004) and spreads rapidly by rooting at stem nodes (Mawhinney 2004) and is therefore likely to be self sustaining.	H	MH
Time to reproductive maturity?	It spreads rapidly by rooting at stem nodes (Mawhinney 2004), and vegetative fragments dispersed by floodwaters can quickly produce roots and become established as new plants within a matter of days (Lucy et al 1995). Vegetative propagules can become separate individuals in under a year.	H	MH
Dispersal
Number of mechanisms?	Seeds and vegetative fragments are dispersed via flood.	MH	MH
How far do they disperse?	Dispersal via attachment to birds or flood waters (Leigh & Walton 2004) could disperse seeds greater than 1 km.	H	MH

Note: Phyla canescens has previously been regarded as a synonym of P. nodiflora, and although the two species are similar and closely related, they are separate species (Julien et al 2004, Munir 1993).

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