serotinous UK /sɪˈɹɒtɪnəs/US /səˈɹɑtɪnəs/ adjective2 •Of conifer cones: requiring the heat of a wildfire to open, in order to disperse its seed. •Synonym of serotine (“developing at a later time or later in a season, especially than is customary with allied species; specifically (botany), of a plant: flowering late in a season”).