 When the plant dies down in summer, the cypselas remain encased between the hardened bracts, presumably safe from harvester ants.After the first rain, which usually occurs the next winter, the bracts and pappus on the aerial flowerheads unfold, and the cypselas are dispersed by the wind, while many are gathered by ants.The cypselas in the underground flowerheads however germinate through the dead parts of the flowerhead, and remain protected against the ants.