Panicum decompositum var. decompositumis the only variety occurring in Victoria (see profile under that name). Panicum decompositum var. tenuis (F.M.Bailey) has smaller spikelets and occurs in NT, Qld and northern NSW and Queenslalnd. The distinction between the two varieties is not accepted by all authorities.
Source:
Walsh, N.G. (1994). Poaceae. In: Walsh, N.G.; Entwisle, T.J., Flora of Victoria Vol. 2, Ferns and Allied Plants, Conifers and Monocotyledons, pp. 356–627. Inkata Press, Melbourne.
