A dry river bed accommodating a broad organic staircase is the central landscaping feature in the Acacia Garden - and it doubles as a history book.
At each landing between the cascading granite steps are marble inlays depicting the leaves and flowers of different acacias (or wattles) by artist Stuart Green, who also etched seed pods into individual steps.
From the bottom you ascend through time as the evolutionary development of the Acacia genus is illustrated in the mosaics, beginning with one of the most primitive species still in existence, Brown's wattle (Acacia browniana).
Walking up the stairs you will see mosaic representations of sandpaper wattle (A. denticulosa), wireweed wattle (A. coriacea), Dandaragan wattle (A.splendens) and blunt-tipped wattle (A. truncata) and at the top is the most highly evolved, flat wattle (A.glaucoptera).
Acacias are the largest group of woody plants in Australia, with over 1200 species occurring in habitats ranging from desert to riverine and displaying habits from groundcovers to trees.
They comprise the largest native genus in Western Australia, with most favouring arid or semi-arid zones, hence the design choice of a dry watercourse for the hard elements of the Acacia Garden landscape.
As Australia's floral emblem, wattle is portrayed as having yellow puffball blossoms but in fact acacias are diverse in flower and leaf shape. Some acacias have 'true' leaves; others have lost their leaves and have flattened stems or phyllodes - a water-conserving adaptation to cope with heat and drought.
For the 3,600 square metre Acacia Garden, the showiest species or those traditionally used for food and medicine or to make spears and implements by Aboriginal people were chosen. Today certain species are commercially valuable as timber and stockfeed, and acacias are also a staple in most revegetation projects.
Worldwide, the highest concentration is in Western Australia's wheatbelt. The Shire of Dalwallinu is dominated by acacias, boasting 185 species within a 100 kilometres radius - roughly equal to the number recorded in either the whole of Africa or the total in North and South America combined.