Biosecurity Spotters logo

Sea spurge (Euphorbia paralias)

Sea spurge forms dense infestations on Australian coasts and offshore islands, where it can become the dominant plant and displace native vegetation. It changes dune structure, can reduce beach nesting sites for shorebirds, and has toxic sap that can irritate skin and eyes.

Key facts

Type: Weed, herb.

Native to: Western and southern Europe, northern Africa and western Asia.

Established in: NSW, VIC, TAS, SA, WA.

Other names: Spurge.

Best time to act: Mass germination occurs in spring and summer, so seedlings can be pulled the following year before flowering, which usually occurs from September to June.

Identification

  • It is a long-lived plant with upright or semi-upright stems, usually 20 to 70 cm tall and occasionally up to 1 m, growing from a woody base.
  • The hairless, bluish-green stems are often fleshy, 2 to 5 cm thick, and contain milky white sap.
  • Crowded, stalkless bluish-green leaves overlap along the stems; they are relatively thick and hairless, and may turn reddish as they age.
  • Tiny yellowish-green flowers are clustered near branch tips in cup-shaped structures with four orange, crescent-shaped glands.
  • The green capsule is about 3 to 5 mm long and 4.5 to 6 mm wide, and contains three pale grey or whitish seeds.
  • Look-alike: Similar weedy spurges include False Caper, Caper Spurge, Sun Spurge and Petty Spurge; Sea Spurge is usually found at sandy coastal sites and has somewhat fleshy leaves.
  • Look-alike: False Caper is the most similar, but its flowers are borne in groups of two or three; Caper Spurge, Sun Spurge and Petty Spurge are short-lived plants with a single main stem.

Where it grows

In Australia it occurs in coastal districts and offshore islands of temperate regions, including New South Wales, Victoria, Tasmania, South Australia and southern and south-western Western Australia, most commonly on coastal sand dunes.

Why it matters

  • It can rapidly form large, dense infestations in open coastal communities and become the dominant plant, displacing native vegetation.
  • Foredune infestations stabilise dunes and prevent natural sand movement inland, creating a different dune structure from that formed by native species.
  • It can reduce the availability of beach nesting sites for shorebirds, including the endangered Hooded Plover.
  • Its poisonous milky sap can highly irritate skin and eyes.

How it spreads

  • Mature fruits open explosively, scattering seeds a few metres from the parent plant.
  • Buoyant seeds disperse over long distances in seawater and can remain viable after floating for several years.
  • People can spread seeds on vehicles, in ballast water, in contaminated sand or soil, and via beach-grooming equipment.

Control options

  • Check with the local council or state or territory weed management agency about control requirements; long-term control can be difficult because seeds may arrive from the ocean.
  • Hand-pull smaller plants and dig out larger ones, wearing protective clothing to shield skin and eyes from the irritating sap.
  • Where appropriate, allow mass-germinating seedlings to thin naturally, then pull them the following year before flowering; follow up for new seedlings and regrowth from broken taproots.
  • Spot spraying with registered herbicides may suit larger infestations or sites where hand-pulling disturbance is unacceptable; glyphosate and metsulfuron-methyl have been used successfully.

Hygiene and washdown

  • Avoid moving seeds to new sites on vehicles or beach-grooming equipment, or in contaminated sand or soil; ballast water can also spread them.
  • Inspect and clean vehicles, plant and footwear before leaving an infested area, paying attention to tyres, radiators, belly plates, tracks and floor mats.
  • Wash down at a designated bay where runoff is contained and can be monitored for seedlings.
  • Record each washdown so the client has evidence of clean entry and exit.

Classification by state

  • Australia (national): No national listing. Managed under state and territory law.
  • Queensland: Not prohibited or restricted. Not listed as prohibited or restricted matter in Queensland. Everyone must also take all reasonable and practical steps to minimise its risks (the general biosecurity obligation).
  • New South Wales: Regional priority in 3 of 11 regions. Regional priority weed in Hunter, North Coast, South East. The general biosecurity duty applies: anyone dealing with it must prevent, eliminate or minimise the risk it poses.
  • Victoria: Not declared. Not declared under the Catchment and Land Protection Act 1994. Other Victorian laws may still apply.
  • South Australia: Not declared. Not declared under the Landscape South Australia Act 2019. Other laws may still apply.
  • Western Australia: Permitted, not declared. Listed as a permitted organism in WA, so it can be brought in, but it is not a declared pest.
  • Tasmania: Not declared. Not a declared weed in Tasmania. Other laws may still apply.
  • Northern Territory: Check NT list. There is no NT weed profile for it. Check the NT declared weeds list for its current status.
  • Australian Capital Territory: Not declared. Not declared under the Biosecurity Act 2023 (ACT). A general biosecurity duty still applies.

Legal obligations

Every state and territory places a duty on landholders and people working on land to prevent the spread of invasive species, such as the general biosecurity obligation in Queensland and the general biosecurity duty in New South Wales. Declarations and control requirements differ between states and local government areas, so check the current official list before work starts.

  • New South Wales: Biosecurity Act 2015 (NSW), administered by NSW Department of Primary Industries and Regional Development
  • Victoria: Catchment and Land Protection Act 1994 (Vic), administered by Agriculture Victoria
  • Tasmania: Biosecurity Act 2019 (Tas), administered by Biosecurity Tasmania
  • South Australia: Landscape South Australia Act 2019 (SA), administered by the regional landscape board
  • Western Australia: Biosecurity and Agriculture Management Act 2007 (WA), administered by the WA Department of Primary Industries and Regional Development

Sources