Help Needed As New Plant Discovery Poses Serious Threat To NZ Coastal Ecosystems
The beach weed sea spurge, Euphorbia paralias, has recently been found at one New Zealand beach near Aotea Harbour (Waikato) and may be present at others. If it established in New Zealand this invasive weed is likely to seriously impact the coastal environment.
Sea spurge infestations have caused major environmental problems at many Australian beaches where it displaces native plants and natural patterns of sand movement. It will reduce the recreational value of beaches as it covers areas of bare sand and the sap of sea spurge is white, toxic and sticky. Its seeds can survive for months or years at sea, so it may have arrived here on ocean currents.
The Ministry for Primary Industries, Department of Conservation and Waikato Regional Council have started control of the known infestation site. Work is also needed to determine if the weed has established elsewhere in New Zealand. Survey work is underway in areas near the Aotea Harbour site, but it may be found on many beaches so the public's help is being sought.
Please report any discovery of the species by calling the Ministry for Primary Industries exotic pest line (0800 80 99 66). Please do not disturb the plants, as this could spread the seeds. Take a photo and note the location as accurately as possible (GPS coordinates are ideal). However, if you don’t have access to a camera, take a sample of the plant and store it in a cool humid place (in a sealed plastic bag in a fridge is ideal), being careful to avoid getting the toxic sap on your skin and to not disturb seed heads. Ministry for Primary Industries staff will tell you what to do with the sample once you call the exotic pest line.
Sea spurge is a hardy European shrub that thrives in sand dunes (see photo above by Sarah Beadel, Wildland Consultants). It has multiple stems that are often reddish at the base and support spiky, tightly-packed blue/green leaves which are approximately 4-20mm long and 1-16mm wide. Green flowers bloom at the tips from September to May and the flower stems die off each year. The milky sap that oozes from broken stems is toxic to people and animals. The plants can grow to about 100cm tall in dense clusters.
See a more detailed description on the Network factsheet:
Sea spurge (Euphorbia paralias)
Sea spurge is most likely to be found on or behind the front dune or within flotsam. General easterly currents and drift within the Tasman Sea mean that much of New Zealand could receive sea spurge seed from Australia. However, the most likely areas include northern New Zealand from Cape Egmont to East Cape, with Manakau Harbour to Rangaunu Harbour being particularly at risk. Within the South Island, areas such as Farewell Spit, Golden Bay, Tasman Bay, Southland and Stewart Island are most likely to receive seed.
Sea spurge looks superficially similar to the rare native shore spurge (Euphorbia glauca) and New Zealand linen flax (Linum monogynum). Native shore spurge is easily distinguished because it has much larger leaves (30-80 mm long) than sea spurge. New Zealand linen flax is also easily distinguished because its stems are not reddish at the base and do not exude a milky sap when broken.