Infrared radiation is an ancient pollination signal.

Color and scent are well-known pollinator cues. Some plants also produce heat, but its role remains unclear. Here, we report that plant-generated thermal infrared radiation serves as a pollination signal and describe the underlying mechanisms of heat production and infrared detection. Mitochondrial adaptations heat plant reproductive structures in a circadian pattern, radiating infrared that is sufficient to attract beetle pollinators. Beetle antennae contain infrared-activated neurons with thermosensitive ion channels that are structurally tuned to match host plant thermogenesis. Comparative analyses revealed that infrared is among the earliest pollination signals, and indicate a deep-time transition from infrared-based to color-dominated signaling in flowering plants. Our findings uncover an ancient sensory modality shaping the early evolution of pollination, one of the world's most vital processes linking plants and animals.