Phenological response of plants to temperature varies at the same latitude: case study of dog violet and horse chestnut in England and Poland

We analysed phenological observations of first flowering of early dog violet Viola reichenbachiana and horse chestnut Aesculus hippocastanum at similar latitudes (and hence photoperiod) in the UK and Poland during the 26 years 1970-1995. Temperatures in Poland were significantly colder than in the UK for February and March and significantly warmer in May. Mean first flowering dates of both species were not significantly different between the 2 countries. However, records in the UK were significantly more variable. Both species in both locations showed significant temperature responsiveness although plants in the UK were more responsive than those in Poland. We conclude that locally adapted species may differ in their projected change under future climate warming.