Exposure of seeds to aerosol smoke or crude smoke extracts stimulates the germination of a number of fire-dependent and fire-independent plant species. We now report the identity of a germination-promoting compound present in plant- and cellulose-derived smoke. The structure of this compound, deduced from spectroscopic analysis and confirmed by synthesis, was shown to be that of the butenolide 3-methyl-2H-furo[2,3-c]pyran-2-one (1). Here we show that 1 promotes germination of a number of plant species at a level similar to that observed with plant-derived smoke water.