Ants and flowering plants’ evolutionary histories have been crossing paths for at least 120 million years. The most spectacular examples of interactions between ants and plants are seen in the so-called ‘ant plants’, or myrmecophytes, which arose only in the last 15 million years. Ant-plant symbioses involve plants with modified structures (domatia) that house ants, in return for protection or extra nutrients, and sometimes also the physical or chemical removal of competing plant species. Oxford Botanic Garden has a long history of cultivation of ant plants. We are currently expanding our collection to support research carried out by Dr Guillaume Chomicki at the Department of Plant Sciences into the field ecology, physiology and genomics of these plants. This work is exploring the mechanisms involved in the specialisation and breakdown of ant-plant mutualisms as model systems to understand the evolutionary dynamics of co-operation among species.