Category: Feature Weeds

History

Ecologist Peter Heyligers reported in The Western Australian Naturalist (Vol 18(1)) in his article Sea spurge (Euphorbia paralias), a strandline pioneer new to the Perth region:

In October 1987 I found a single plant of another introduced strandline pioneer, Sea Spurge, established at Coogee Beach, not far from Woodmans Point. Its presence there, however, was short-lived; when I visited this beach again in September 1988, severe erosion of the upper beach and foredune was evident and the Sea Spurge plant, along with the neighbouring vegetation, had disappeared. No seedlings were found, and an inspection of beaches in the vicinity of Woodmans Point located no other Sea Spurge plants. Nevertheless, I expect that sooner or later this species will turn up again in the Perth region”

His observation ran true, and it’s now a dominant foredune invader as far north as Lancelin, while was previously known to be in the east to Eucla.

Euphorbia paralias, sea spurge, is native to southern Europe and north Africa and was first recorded in Western Australia herbarium^# in Albany in 1927 on the shores of King George Sound.  Seeds are buoyant and its quite likely that seeds arrived with shipping movements to the Port of Albany as the weed was soon after found at Port Victoria in South Australia (Heyligers 1989).   

Ecology biology and phenology

Sea spurge is a perennial coastal coloniser, surviving well on beach sand and has a deep tap root that enables it to survive the extremes of coastal dune movement.  Its not uncommon to find clusters of what appear to be sea spurge seedlings, only to find they are the tips of a mature plant deeply buried in sand.  Bushes are between 20cm-1m high, depending on the sand.  Like most Euphorbia species, sea spurge is not palatable to vertebrates as they exude a toxic, and bitter latex sap that can cause irritation to skin and eyes.  Sea spurge is a prolific fruiter, with 1000s of seeds produced each year in summer.

Sea spurge in Western Australia is found on most southern beaches and can form dense stands.  In eastern Australia, particularly Tasmania sea spurge deprives shore birds of habitat, and is a direct threat to at least three migratory birds. 

Legislation

Sea spurge is not a declared species in Western Australia.

Control Options

Sea spurge is often controlled with herbicide and hand weeding, but a persistent seed bank will mean ongoing efforts are required. 

Sea spurge is a target for biological control, with a rust fungus released in 2020 (https://research.csiro.au/nswweeds/sea-spurge).  Trial sites for rust establishment are being monitored in Tasmania, Victoria and NSW.  It is anticipated that sites for rust establishment will be set up in Western Australia in late 2023.

^#Notes in Heyligers (1989), but this record is not available on the Atlas of Living Australia.

References

Heyligers, P (1989).  Sea spurge (Euphorbia paralias), a strandline pioneer new to the Perth region.  The West Australian Naturalist 18(1) p1-6.  https://www.biodiversitylibrary.org/item/275547

passiflora stinking passionfruit

Taxonomy

Carpobrotus sp. (Aizoaceae) are commonly called pigface in Australia, and it’s a complex genus that consists of several species, that most people think all are native.  Carpobrotus edulis, commonly called Hottentot fig or Cape fig, is a widespread perennial succulent that originates in South Africa and has naturalised in most Mediterranean countries in the world.  Its particularly weedy on sandy soils in coastal areas, and can form monocultures in winter-wet depressions and sandy paddocks.  Its spread in Western Australia has been assisted by widespread amenity plantings facilitated by several local government areas and contractors.  Carpobrotus aequilaterus commonly called Chilean pigface is less common, but not less aggressive as an invader.  Also widespread throughout Mediterranean, but its origin is less clear.  Most likely to be from South Africa, but it’s seen as a species unique to California and has been present there the 1600s (Vila et al 1998). 

The native Carpobrotus species in Western Australia are:

Carpobrotus modestus.  Inland pigface see https://florabase.dpaw.wa.gov.au/browse/profile/2796

Carpobrotus rossii, Krakalla,found near Shark bay  see https://florabase.dpaw.wa.gov.au/browse/profile/2798

Carpobrtus virescens, found in southern coastal dunes from Shark Bay to Esperance see https://florabase.dpaw.wa.gov.au/browse/profile/2798

All three species will hybridise with the exotic Carpobrotus, and there is concern amongst botanists that it will eventually be impossible to discern native species form hybrids.

Ecology, biology and phenology

When not in flower, C. edulis is a low growing succulent with deep green leaves that resemble fingers.  Usually triangular in section, leaves are variable in length from 1-15cm.   Flowers are large, 5-6cm wide, yellow and present from September – January.  Individual flowers persist for about a week, and then petals wither and the fruit can persist for several months where its either eaten by wildlife or falls below the plant.  Carpobrotus fruits are edible and can sometimes be found pickled at specialist gourmet food stores and recipes online.   

C. edulis readily hybridises with native species, and back again and therefore much of the Carporbrotus seen in gardens are a hybrid of unknown ancestry.  Due to challenges in taxonomy, its only in recent years that revegetation programs have ensured Carpobrotus used in coastal revegetation are sourced from stock propagated from the native C. virescens and not C. edulis or hybrids.  

Hybrid Carpobrotus flowers are variable in colour, from apricot to deep purple.  C. edulis in its pure form is always yellow.

Legislation

Unfortunately, it’s not a reportable plant, but its still sold in mainstream nurseries. 

Control options

C. edulis is shallow rooted, so can be easily hand pulled in small areas but will regrow from any fragments.  Herbicide may be required for larger areas.  The seed is short-lived but may persist for 2-3 years.  Succulent species aren’t often successfully managed with control burns.

Found Carpobrotus edulis?

If you find Carpobrotus edulis, report it to DPIRD by MyPestGuide Reporter or iNaturalist.  Reporting contributes to knowledge of the species range. 

References

Hussey, B.M.J., Keighery, G.J., Dodd, J., Lloyd, S.G. & Cousens, R.D. (2007) Western Weeds. A guide to the weeds of Western Australia. 2nd Edition. The Plant Protection Society of Western Australia, Victoria Park.

Vila, M., Weber, E., & D’Antonio, C.,M. (1998). Flowering and mating system in hybridizing Carpobrotus (aizoaceae) in coastal california. Canadian Journal of Botany, 76(7), 1165-1169.

Mexican poppy in Western Australia is the common name for two species of invasive poppy from the Papaveraceae family: Argemone mexicana and Argemone ochroleuca subsp ochreleuca.  Both species originate in Mexico and the range extends to central America and into southern Texas.  Both species have similar in appearance but A. mexicana petals are orange in colour while A. ochroleuca is pale yellow to white.  First recorded in Australia herbaria in 1882 around Moree and Gunnadah, it has thought to have arrived as a contaminant in imported wheat (Parsons & Cuthbertson, 2001).  First recorded in Western Australia in 1921 at Beverley in the Avon Valley catchment in southern Western Australia, but its highly invasive range is Pilbara region, particularly along water courses.  Occasional plants are found in southern WA but populations rarely persist.

Taxonomy

Argemone ochroleuca Sweet subsp. ochroleuca, Argemone Mexicana L.

The most prevalent species in Western Australia is A. ochroleuca subsp. ochroleuca.  From Florabase:

Annual, herb, 0.3-1 m high, spiny, with yellow latex. Fl. white-cream-yellow, Feb to Mar or Jul to Nov. Red/white/grey sand, red-brown clay loam. Creek edges, riverbanks, roadsides.

Ecology, biology and phenology

Mexican poppy has naturalised throughout Australia and in southern Africa.  Its commonly a weed of highly disturbed areas such as roadsides and mining areas, but large infestations are found along seasonal sandy river beds and poorly managed pastures.  The sap is toxic, but it’s not usually grazed by livestock due to the numerous spines on all plant tissues and the bitter sap, but the seeds could result in animal poisoning if introduced in ground feed.  Primary concern for agriculture is the contamination of cereal crops, and in southern India and southern Africa and there have been several cases of human poisoning and death following ingestion of wheat flours made with high levels of mexican poppy seed.  It is also associated with epidemic dropsy, a lymphatic condition resulting in fluid retention in the legs and feet (see https://en.wikipedia.org/wiki/Epidemic_dropsy).

Mexican poppy is an annual species, germinating in late Autumn and producing flowers between November and December.  The species is self-fertile and after flowering, an ovoid seed pod forms containing up to 400 seeds that can persist for several years.  In northern Australia, germination could be variable depending on rainfall and it’s not uncommon to have huge flushes of germination following cyclonic events. 

Legislation

Argemone mexicana is a declared pest in the state, prohibited entry although it has been recorded from several locations.  Argemone ochroleuca is a permitted species, and although its highly undesirable weed there is not control category assigned. 

Control options

Several control options are listed on the DPIRD website https://www.agric.wa.gov.au/herbicides/mexican-poppy-control

Found Mexican poppy?  Report it…