These trees dominate the surviving native vegetation through most of Mallee, (except for swamps and areas along waterways).

The Mallee is, for all practical purposes, completely flat and very low-lying: in fact, for long geological periods the whole region was inundated by the ocean.

The soils are generally very infertile and sandy: the better ones on more stabilised sand dunes in the east are slightly loamy and pink to light brown and have been able to support wheat and barley growing as a result of the development of superphosphate and other fertilisers.

The Mallee has no surface drainage: the native vegetation has so high a rooting density that the rainfall of most years is easily absorbed and the porous sandy soils mean that any excess in an exceptionally wet year will recharge groundwater supplies which tend to be highly saline.

Temperatures in summer are generally very hot: during the Early 2009 southeastern Australia heat wave, Hopetoun reached 48.8 °C (119.8 °F)[3] and the average maxima in January and February are 32.7 °C (90.9 °F).

Hills stated that: "the chief factors involved in the distinction between the Mallee and the country south and east of it are precipitation, evaporation, rock type, porosity of the superficial deposits, drainage away from high areas and supply of water from streams that rise in regions of higher rainfall.

"[4] At the 2011 census, the Mallee had a population of 81,544, most of which live close to the Murray River in the district's two cities, Mildura and Swan Hill.

Ouyen and Murrayville are the main settlements of the central Mallee, while Kerang, Cohuna, Hopetoun and Birchip are the major towns in the south.

Fruit growing along the Murray River exceeds grain crops as the Mallee's major source of revenue.

[12] In the context of the Interim Biogeographic Regionalisation for Australia, the Mallee is spread over parts of both the Murray Darling Depression and Riverina bioregions.