PHENOLOGY OF SEVERAL PLANT SPECIES AT OTTAWA, ONTARIO, AND AN EXAMINATION OF THE INFLUENCE OF AIR TEMPERATURES

Abstract

The apparent base temperature, below which plants do not develop towards flowering, was estimated for 10 of the early flowering woody species by means of a modified linear regression analysis. The relationship between average spring temperatures and developmental rates was examined for the same 10 species. The rate of development towards flowering in Acer saccharinum, A. saccharum, Populus tremuloides, P. grandidentata and Ulmus americana was more closely related to average maximum temperatures while in Acer rubrum and Betula papyrifera it was more closely related to minimum temperatures. Alnus rugosa, Acer negundo and Prunus pensylvanica were not markedly influenced by average spring temperatures. The first dates of flowering are also presented for 36 plant species that were observed during the period 1936–1960 at Ottawa, Ont. The marker plants include 18 trees, 6 shrubs, 6 grasses and 6 other herbaceous and weedy species.