Invasiveness Assessment - Sea spurge (Euphorbia paralias) 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 Sea spurge.

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: Sea spurge
Scientific name: Euphorbia paralias

Question	Comments	Rating	Confidence
Establishment
Germination requirements?	Germination occurs on mass in spring and summer (Blood 2001).	MH	MH
Establishment requirements?	While most common on fore dunes within the flotsam deposit, plants can establish in the swale behind the dunes, most commonly associated with an existing large plant (Heylinger 2002). They may remain small but do establish, therefore the species is able to establish under moderate shade.	MH	H
How much disturbance is required?	A pioneer species, most invasive on open sand which would have little to no competition with other species. It has been observed establishing however, behind the fore dunes within other existing vegetation (Heylinger 2002). These coastal systems while it is natural disturbances are considered highly disturbed.	ML	H
Growth/Competitive
Life form?	Other; perennial herb (Blood 2001)	L	MH
Allelopathic properties?	The species is known to contain secondary compounds there is no evidence reported of allelopathy however (Abdelgaleil et al 2001; Jakupovic et al 1998; Sayed et al 1980).	L	MH
Tolerates herb pressure?	The sap of the plant contains irritating and cytotoxic compounds which have been shown to cause inflammation of a mouse’s ear (Sayed et al 1980). This is likely to deter grazing species. Able to regrow if buried by sand and new stems grow to replace the old stems that die after flowering (Heylinger 2002). On the Canary Islands it is reported to be fed on by the larvae of Hyles tithymali (Hundsdoerfer & Wink 2006). Whilst grazing species may be deterred from this plant by irritants in the sap, the ability to regrow suggests that the species is able to recover from herbivore pressure.	H	MH
Normal growth rate?	Has rapid early growth (Blood 2001). While no specific measurements are reported, it is presumed with this description of early growth the species growth would be at least be equal to that of other competitive herb species.	MH	MH
Stress tolerance to frost, drought, w/logg, sal. etc?	Tolerant of salt water (Blood 2001). Drought tolerant (Blood 2001). Reported tolerance to varying ground water levels (Blood 2001). Therefore shows some tolerance to waterlogging. Able to regrow if buried by sand and as the above ground stems die after flowering to be replaced by new stems (Heylinger 2002). Therefore most damage to the above ground stems, from fire, frost or grazing could presumably be recovered from.	H	MH
Reproduction
Reproductive system	Able to reproduce sexually producing seed and vegetatively with root fragments (Blood 2001).	H	MH
Number of propagules produced?	There is some variation in the species reported seed production, Blood (2001) reports 5 000. Heylinger (2002) however, states that seed production is variable and dependent upon conditions, but plants are capable of producing 100 stems, 80 fruits per stem and three seeds per fruit and therefore 20 000 seeds per plant. While there is variation in the reported seed production capability there is agreement that the plant is capable of producing more than 2 000 seeds per season.	H	H
Propagule longevity?	After floating in salt water for 2 years 50% were found to be viable, with none found to be viable after 6 years, however stored seeds have been found to stay viable for at least 7 years (Heylinger 2002).	ML	H
Reproductive period?	Unknown.	M	L
Time to reproductive maturity?	Unknown.	M	L
Dispersal
Number of mechanisms?	The seeds are initially released explosively and then may be dispersed by wind, water and accidentally by people (Blood 2001; Carr, Yugovic & Robinson 1992; Heylinger 2002)	MH	H
How far do they disperse?	The effective range of the initial explosive release has been found to be 2 m. While the potential dispersal by water and more specifically oceanic currents is much more than 1 km, as the seeds can remain viable and buoyant in salt water for many years. The species has been reported to have spread from the Australian mainland to Lord Howe Island, which is 850 km ENE from Jervis Bay (Heylinger 2002).	H	H

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