Germination of Aesculus hippocastanum seeds following cold-induced dormancy loss can be described in relation to a temperature-dependent reduction in base temperature (T ) and thermal time.

•  The effect of moist stratification at cool temperatures on Aesculus hippocastanum (horse chestnut) seed dormancy release and subsequent thermal time requirement for germination has been investigated. •  Germination performance following over 50 different treatments, each varying in time and temperature of stratification and germination to a total test time of over 3 yr, was used to develop a predictive model for dormancy release and germination. •  Stratification at 2-16°C caused a reduction in base (minimum) temperature for germination (T ), being fastest at the colder temperatures. Using the sigmoid relationship between rate of reduction in T and stratification temperature, seed germination can be predicted in relation to thermal time accumulation above a gradually reducing T . Newly shed unstratified seeds, seeds with reduced viability, and seeds on the brink of germination because of T being close to stratification temperature, did not conform to the model. •  T is not constant during dormancy release in horse chestnut seeds. A reduction in T in response to cold stratification may be characteristic of summer annuals, suggesting future applications for this approach in seed ecology studies.