Organismal persistence attests to adaptive response to environmental variation.  Diversification bet hedging, in which risk is reduced at the cost of expected fitness, is increasingly recognized as an adaptive response, yet mechanisms by which a single genotype generates diversification remain obscure.  The clonal greater duckweed, Spirodela polyrhiza (L.), facultatively expresses a seed-like but vegetative form, the “turion”, that allows survival through otherwise lethal conditions.  Turion reactivation phenology is a key fitness component, yet little is known about turion reactivation phenology in the field, or sources of variation.  Here, using floating traps deployed in the field, we find a remarkable extent of variation in natural reactivation phenology that cannot be explained solely by spring cues, occurring over a period of at least 200 days.  Under controlled laboratory conditions, we find support for the hypothesis that turion phenology is influenced jointly by phenotypic plasticity to temperature and diversification within clones.  Turion “birth order” consistently accounted for a difference in reactivation time of 46 days at temperatures between 10° and 18°C, with early birth-order turions reactivating more rapidly than late birth-order turions.  These results should motivate future work to formally evaluate turion phenology variance as a bet-hedging trait.