Eight different vegetation associations consisting of at least 176 different plant species have been identified, 30 of those are orchids. One species, Cradle of Incense (Prostanthera eurybioides) is considered nationally endangered.
The eight different vegetation associations are:
Broombrush, Honey Myrtle and Dryland Tea Tree
Widespread throughout the park, but the mix of these three species varies considerably through the park, depending on soil type.
Hedge Wattle, Broombrush, Honey Myrtle, Dryland Tea-Tree
Only on the rocky outcrops, also dominated by Spoon-leaved spydridium and Drooping sheoak.
Pink Gum, Desert Banksia and Silver Banksia
This occurs only along the edge of the road on the northern boundary. It has the most divers understorey of all the associations in Mont Monster.
Yellow Mallee, Honey Myrtle and Dryland Tea-Tree
Occurs away from the porphoritic outcrops over shallow soils.
Pink Gums, Golden Wattle, Honey Myrtle and Dryland Tea-Tree
Occurring on the deep alluvial soils, this has a dense and diverse understorey.
Peppermint Box and White Mallee
With emergent Pink Gum and Golden Wattle it is the most wide-spread associated in the park and has a large mix of species with a sparse understorey.
Peppermint Box and South Australian Coastal Mallee
Only found along the south-eastern boundary of the park with limited and sparse understorey.
Blue Gum and Peppermint Box
Occurs in the deep alluvial soils between the porphoritic outcrops. The trees are amature, well spaced and have no understorey.