Sea Spurge (Euphorbia paralias)

Family: 

Photo: (c) Frank Vincentz CC BY-SA 3.0 license

Growth Habit: A long-lived herbaceous plant with several upright or semi-upright stems, usually 20-70 cm tall, growing from a woody base. Its stems are somewhat fleshy, hairless, bluey green, contain a milky sap, and usually divide into branches near their tips. The stalkless bluey green leaves, 5-30 mm long and 2-15 mm wide, are crowded or overlapping along the stems. Stems and leaves turn red with age. The stems die off after flowering and are replaced by new shoots from the woody base.

Type of Plant: Erect perennial herb that grows up to one metre high. 

Photo: (c) Zeynel Cebeci CC-BY-SA-4.0 license

Flowers: Tiny cup-like, inconspicuous, yellowish-green, ‘flowers’ are clustered near the tips of the stems and have a large stalked ovary.

Fruit/Seeds: The fruiting capsules is 3-5 mm long and 4.5-6 mm wide, each containing three seeds. These smooth seeds are egg-shaped to rounded and pale grey to whitish. A single plant has the potential to produce 5,000 seeds per year.

Dispersal: Sea Spurge disperses via seed. The fruit open explosively when mature and expel the seeds short distances. Seeds are also buoyant in sea water, and can be spread very large distances by ocean currents. Seeds can remain viable in sea water for several years. Sea Spurge can also be spread via boats, ship ballast water, root fragments and seeds on vehicles like 4WDs, and contaminated soil and sand. 

Distribution: A weed of coastal environs and offshore islands in the temperate regions of Australia. It occurs on free draining sandy soils on beaches, around estuaries, through dune fields, in coastal herbfields, grasslands, heaths and shrublands, and may also grow along rocky shorelines and in sand-filled cracks between rocks. Found on coasts right around Tasmania.

Status: Currently not declared in Tasmania but is a significant environmental weed.

Weed Impact:

  • Establishes dense infestations on upper beaches and fore-dunes.
  • Reduces native flora biodiversity. 
  • Alters natural shape and structure of beach and dunes.
  • Adversely impacts on the nesting habitat of a range of threatened and other shorebirds.
  • May impact on sites with Aboriginal heritage values.
  • Reduce amenity and beach access.
  • Sap is toxic.
  • Long distance dispersal by ocean currents mean infestations can establish in inaccessible and remote coastal environments. 

Control Methods:

  • Complete eradication of Sea Spurge is nearly impossible due to sea-borne, long distance dispersal of propagules and seeds. 
  • The capacity for an ongoing control program is essential.
  •  Do not drive through dunes or along infested beaches. Damage to dunes and vegetation encourages colonisation by Sea Spurge.
  • Adopt appropriate hygiene and washdown practices for vehicles and boats.
  • Control programs and methods will depend on the extent of the infestation and practical feasibility of undertaking control activities. 
  • Control of large infestations may not be feasible and targeted control or eradication programs of high value conservation or recreational sites might be the best option. 
  • Manual Removal. Hand pulling, especially of seedlings, is possible for small infestations. Care must be taken to remove all the root system, as new crowns can re-establish from root sections. PPE – rubber gloves, eye protection and long sleaves are also a must, as the plants sap is toxic.
  • A number of herbicides have been successfully used to control sea spurge, including glyphosate and metsulfuron-methyl. This can be useful where minimal disturbance of sand/soil is important such as around Aboriginal middens. 
  • Biological controls for Sea Spurge are currently being researched by the CSIRO
  • For more information on Sea Spurge and planning your control program look at the Weed Management Guide for Sea Spurge.

N.B. Always check the herbicide label before use.