Var. australe has flowers with sepals as long as petals, as opposed to petals longer than sepals found in the typical variety, it also has smaller fruits and caudate-acuminate leaf lobes (de Jong 2019).
RHS Hardiness Rating: H5
Var. australe in likely to be rather rarer in cultivation than previously supposed. It is known largely from relatively recent introductions made under the name, codes and numbers BBJMT 291 and BCJMM 291, both made in Gifu Prefecture, Honshu, in 2005 and 2007 respectively. Both expeditions comprised staff from the Royal Botanic Garden Edinburgh and the Howick Arboretum in the United Kingdom, and the Quarryhill and Polly HIll Botanic Gardens in the United States, and they have been distributed relatively widely through major collections in Europe and North America. Unfortunately, neither of these collections represent this taxon, and both are referable to Acer micranthum.