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  Comments about the monotony of the mallee are a cultural commonplace. There are, however, a surprising variety of mallee trees, with distinct patterns of distribution across the whole region known simply as "the Mallee". To begin at the beginning, there are two foundational events in our geological past that explain some of this unexpected diversity. The first is a marine incursion into the western part of the Murray-Darling Basin (ca. 6 MYA). Late Miocene and Early Pliocene retreats by the Southern Ocean left its seabed of sedimentary deposits called the Parilla Sand Formation.  The second is a freshwater submergence of much of the same area by the palaeo-Lake Bungunnia (ca. 3.5 MYA). Late Pliocene and Early Pleistocene faults and uplifts blocked the drainage of the Murray and Darling Rivers to the sea. The lake overlaid the Parilla Sand with siltier sediments of Blanchetown Clay and some Bungunnia Limestone, before finally breaching the tectonic barriers and emptying out....

  Australian eucalypts have traditionally been named according to their bark. Smooth-barked species are generally called Gum or Mallee. Rough-barked species are known as Box or Stringybark. There are four smooth-barked eucalypts, three Gum and one Mallee, that typify different parts of the borderlands of Western Victoria. They have become the predominant canopy-trees in areas with particular geographic characteristics. From north to south, these are: (i) Dumosa Mallee , Eucalyptus dumosa , sometimes called White Mallee, is the most widespread of the Mallees. It grows in a great arc across southeastern Australia, from south of Dubbo and Louth in NSW, through northwestern Victoria and the Murray Mallee of SA, to Eyre Peninsula and the Flinders Ranges. Early explorers were not impressed. John Oxley's Journals of Two Expeditions into the Interior of New South Wales  (1820), mentions "those dreadful scrubs of eucalyptus dumosa". Allan Cunningham, his accompanying botanist, is ...

  Midway along the Highway from Melbourne to Adelaide, between Nhill and Kaniva, the road crosses a series of parallel sandhills. Lawloit Ridge is the steepest of these phenomena, which are actually "stranded coastal dunes". They are remnants of a geological past when much of the Murray-Darling Basin lay under the Southern Ocean. It was a time when global sea levels fluctuated according to a climatic cycle. Over millions of years, they fell when polar ice sheets froze (glacials) and rose when polar ice sheets melted (interglacials). The last period when marine flooding of southeastern Australia reached its maximum was approximately 6 million years ago (MYA).   1. 2018, 'Mallee Dunefields of the Murray-Darling Basin', ecological associates pty ltd, Kerang Vic.  2. 2016, CV Murray-Wallace, Coastal Landscapes of South Australia , Adel Univ Press, p 149.  3. 2022, Wimmera Catchment Management Authority, <wcma.vic.gov.au> Since that peak, the ocean has periodically ...

There are three main types of Casuarinaceae  growing in western Victoria. Ranging from the southwest coast (Southern Ocean) northwards to the Milewa Mallee, each species tends to occupy its own geographic zone. Nearest to the sea is the Drooping Sheoak, Allocasuarina verticillata, (formerly Casuarina stricta ), also called the Coast Sheoak. In the middle zone of the Wimmera is the Buloke, Allocasuarina luehmannii , sometimes spelled Bull-Oak. Farthest inland is the Belah, Casuarina pauper , (so-named because it is a smaller version of Casuarina cristata that occurs in New South Wales and Queensland). Drooping Sheoak, Buloke, and Belah also abut and cross over the border into South Australia. Casuarinas resemble pine trees with their needle-like foliage and woody seed-cases. The foliage is actually made up of segmented branchlets, with tiny blades (residual leaf tips) radiating from each joint of the thin stem. Their distinctive appearance is described in the word 'casuarina', w...