SIBBALDIA: 33 AN OCCASIONAL SERIES OF HORTICULTURAL NOTES FROM THE RBGE, No 2. PHENOLOGICAL MONITORING AT ROYAL BOTANIC GARDEN EDINBURGH G.H. HARPER, D.G. MANN & R. THOMPSON* Phenological monitoring at the Royal Botanic Garden Edinburgh (RBGE) began in the mid 19th century, and is now being developed as a number of projects. In view of the wide range of plant- climate interactions, it is recommended that projects are designed with clear and limited objectives, and are then conducted consistently and to a high standard over a long period. The projects at RBGE are outlined, and the suitability of botanic gardens in general for phenology is discussed. A distinction is drawn between 'organism phenology' and 'population phenology', and also between 'extensive' and 'intensive' approaches to project design. The variety of possible projects is illustrated by a number of completed and on-going projects in the UK, USA and northern Eurasia. It is suggested that botanic gardens can enhance their service to society by becoming phenological monitoring stations. INTRODUCTION Phenology is the study of seasonal phenomena. The ties between phenology and taxonomic botany have a venerable history. No-one doubts that Linnaeus is the 'father' of modern botanical nomenclature, but he has also been credited with introducing the word `phenology' (Gunn, 2003); of course, many others before him had made phenological observations, e.g. of the dates of wine harvests (Ladurie & Baulant 1981). In his Philosophia Botanica Linnaeus listed dates for first flowering, leafing, fruiting and leaf fall, and recommended that 'Floral calendars should be completed every year in every province, according to the leafing, flowering, fruiting and leaf-shedding, with simultaneous observations of the climate, so that it may be ascertained how regions differ among themselves' (Linnaeus 1751, p. 297). The history of an interest in climate—plant interactions at the Royal Botanic Garden Edinburgh (RBGE) dates from about a century later, when the first phenological project (or at least, the first of which we have a record) was set up in the Garden. It is the purpose of this article to discuss the role of phenological research at RBGE and in botanic gardens in general. After a brief review of the potential scope of phenology, past and current projects at RBGE will be described along with a discussion of botanic gardens as sites for phenological study. * Geoff Harper is a member of the Science staff at RBGE, working on the Pandora Rosaceae database, and is also a part-time volunteer phenologist. Address: Royal Botanic Garden Edinburgh, 20A Inverleith Row, Edinburgh EH3 5LR. E-mail g.harper@rbge.org.uk David Mann is a member of the Science staff at RBGE, leading research on diatoms. Address as above. E- mail d.mann@rbge.org.uk Roy Thomson is Professor of Geology in the Department of Geology and Geophysics at the University of Edinburgh. Address: Department of Geology and Geophysics, Edinburgh University, West Main Road, Edinburgh, EH9 3J W. E-mail roy@ed.ac.uk