The phases of the annual cycles of certain flora and fauna have been known throughout history to be influenced by climate. Many diaries and garden records from past centuries, including those of the Armagh Observatory, give dates of phenological events such as bud burst, first flowering and leaf fall as well as the return of migratory birds such as the cuckoo. This type of material can help to provide proxy climate data for periods when no instrumental records are available, and also give valuable knowledge on how our changing climate is affecting the natural world today.
In the mid-twentieth century, a number of phenological gardens were set up in Europe with the intention of employing observations of certain common species of plants as indicators of climate change. They used genetically identical material provided by a central coordinating laboratory in Germany. Four such gardens were established in Ireland, namely those at Valentia Observatory, Co. Kerry; The J.F. Kennedy Arboretum, Co. Wexford; Johnstown Castle, Co. Wexford; and the Botanic Gardens, Dublin. Only one or two such gardens were established in Great Britain at that time and none in Northern Ireland.