Common name: Caustic Bush


Cynanchum viminale subsp. australe beginning to flower. Photo: D. Blumer.View image slideshow

Origin of Scientific Name

Cynanchum – (Greek) kynos – dog, and anchein – to choke; referring to the supposed poisonous properties of some European species in this genus.

viminale – (Latin) long, slender branches.


Cynanchum viminale subsp. australe is a native shrub that grows to 1.3 metres high and 2.5 metres in diameter. The plant has variable forms from sprawling to erect but can form dense mounds in ideal environments. The stems are green to silvery-grey and produce copious amounts of caustic milky fluid when cut or broken, giving rise to its common name.  

The leaves of the Caustic Bush are only small rudimentary leaves that appear on new stems and then perish as the stems mature, so the plants appear leafless. The unusual form of this species can make it an interesting inclusion in a garden with the right growing conditions. 

The Caustic Bush is one of the few true succulents found in Western Australia. These plants have evolved to survive in dry, arid or harsh environments, store water in their stems and can hold their form during extended dry periods without any severe loss of condition.  

From January to November small starry, whitish to pale yellow flowers appear on stalks along the stem. These waxy flowers are lightly perfumed and can be in seen in clusters of up to ten flowers but are rarely prolific.  

The subspecies australe is widely distributed in Western Australia from the Central West Coast, Kimberley, Ningaloo, Pilbara and Shark Bay. It is mainly found associated with red lateritic soils where it commonly grows in rock crevices, or on sandy soils over sandstone or limestone.  

Horticultural tips

  • Propagation is most successful from cuttings.  
  • Adapts to cultivation in semi-arid, arid and temperate regions but can be slow to establish.
  • Requires warm to hot sites which receive plenty of sunshine and soils which are very well drained.  
  • Well suited to cultivation in containers and rockeries. 

For more horticultural tips view our Plant Notes section.

View in Kings Park

Visit Kings Park and Botanic Garden to see Cynanchum viminale subsp. australe in the Mulga beds at the entry to the Western Australian Botanic Garden and in the desert beds within the Roe Gardens (refer to map).

Want more information?

Refer to the profile for this plant on the Department of Biodiversity, Conservation and Attractions' FloraBase online herbarium.

Cynanchum viminale subsp. australe in Kings Park. Photo: D. Blumer. Cynanchum viminale subsp. australe is a shrub that can grow to 5 metres high. Photo: D. Blumer.

Administration car park closure

There will be limited access to the BGPA Administration building and the Kings Park Education and Learning building from Wednesday 15 June 2022 for approximately 8 weeks, due to ongoing Water Corporation works.

Water Corporation works

The Water Corporation is replacing approximately 700 metres of ageing water pipes between Mount Eliza Reservoir and Bellevue Terrace in Kings Park.

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Banksia Carpark in Bold Park is currently closed to the public due to stormwater damage.

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