Phenological Observations on Early Flowers and Winter Temperatures

Abstract

THE relation of temperature to the earliness of the season is too obvious to be overlooked, but methods of representing it numerically are of considerable interest. Since 1878 this has been done for about thirty stations in the United Kingdom by observations on the first appearance of a selected series of thirty flowers. The results have been published in tabular form in the Natural History Journal. Thus the means for all the 900 observations (thirty plants at thirty stations) give an accurate comparison of the relative flowerings in different seasons. The values for the four years (1878-81), reckoning in days from January 1, are 93, 115, 103, and 111, respectively, giving a mean date of 105.3. It will be seen that, when such observations have been conducted over a sufficient period, important values can be deduced as to the relation between the mean temperature and the mean date of flowering; that is, between temperature and vegetable growth. The comparison ought, probably, to be made with the mean temperature of the six months from December to May, the flowers having been chosen so as to be all out by or near the close of the latter month.