Cotton bush (Ptilotus obovatus) in the Western Australian rangelands

Page last updated: Monday, 5 February 2024 - 1:03pm

Cotton bush (Ptilotus obovatus) is one of many plant species found in the Western Australian rangelands. This page provides a summary of the plant's value for pastoralism. Pastoral lessees and station managers can use this information to assess pasture condition and trend.

Indicator value

Cotton bush is best regarded as an intermediate species on its own. Populations of cotton bush fluctuate considerably and responsively to seasonal change. 

Cotton bush is a fairly reliable indicator of good pasture condition in inland mulga communities; closer to the coast, high densities of cotton bush usually indicate fair and poor pasture condition because the more-palatable species in bluebush and mixed shrub communities have been grazed out. The more-palatable and longer-lived plants, such as felty leaf bluebush and flat leaf bluebush, tall saltbush, ruby saltbush, warty leaf eremophila and mulga broom bush (Teucrium teucriiflorum) are more reliable indicators of good pasture condition than cotton bush in inland mulga communities.

Forage value

Cotton bush is palatable to livestock but is relatively short-lived and drops its leaves when suffering water stress. 


Various soils.

General description

Cotton bush is a variable, dense, silver grey-green shrub that rarely grows taller than 70 cm in the Gascoyne and Murchison regions. The coastal form of cotton bush has considerable scrambling potential and may grow taller than 1.5 m when growing under other shrubs or trees. Shrubs commonly have multiple stems originating at ground level. Individual leaves are oval and about 2 cm long by 1cm wide with short stems. A dense felty covering of fine hairs gives the leaves and branchlets their silver appearance. It generally flowers in September and October. The flowers are up to 2 cm in diameter. The flower stalks are retained long after the flower clusters detach and this feature can help to distinguish cotton bush from other plants with a similar leaf-shape and structure.

Contact information

Joshua Foster
Chris Hetherington