Like other wattles, "Acacia pycnantha" fixes nitrogen from the atmosphere. It hosts bacteria known as rhizobia that form root nodules, where they make nitrogen available in organic form and thus help the plant grow in poor soils. A field study across Australia and South Africa found that the microbes are genetically diverse, belonging to various strains of the species "Bradyrhizobium japonicum" and genus "Burkholderia" in both countries. It is unclear whether the golden wattle was accompanied by the bacteria to the African continent or encountered new populations there.