Until recently, 'Eyres Green' was the only commercial cultivar of oldman saltbush available for forage planting and landscape rehabilitation. 'Eyres Green' is believed to be a clonal cultivar of the ecologically and economically important octoploid dioecious species Atriplex nummularia (Lindl.), but its actual identity is unknown. The genetic relationship of the 'Eyres Green' clonal cultivar to the two subspecies A. nummularia ssp. nummularia and A. nummularia ssp. spathulata (Aellen) was assessed using nuclear microsatellite markers, principal coordinate analysis and Bayesian clustering. 'Eyres Green' clustered with ssp. nummularia in all analyses, suggesting that the cultivar was derived from an individual of this subspecies, probably from the north-eastern part of the subspecies' distribution in eastern Australia. Atriplex species are dioecous and substantially wind-pollinated. Plants of the 'Eyres Green' cultivar are female, so risk of genetic contamination from initial plantings is low, but could occur if plantings within pollination distance of natural populations set seed and establish male plants that subsequently become a source of pollen contamination.