THE GROWTH OF WHITE SPRUCE SEEDLINGS IN RELATION TO TEMPERATURE SUMMATION INDICES

The growth (dry weight basis) of white spruce seedlings during their first and second growing seasons was measured. The relationships between seedling growth and time expressed chronologically and in terms of degree days were determined. When degree days were used the relationships were exponential and a zero reference temperature of 36° F. seemed preferable, although temperatures of 34, 38 and 42° F. might be used. The possible advantages of using such a relationship rather than the more conventional one of growth per calendar day are discussed with reference to nursery practices.