Winter injury susceptibility and cold tolerance of current and year-old needles of red spruce trees from several provenances.

(...) Winter injury was found exclusively on current-year needles (i. e., buds and twigs were vitually uninjured), and 34% to 68% of trees were injured each year. Laboratory assessments of cold tolerance of curret and year-old needles of trees representing four red spruce and four balsam fir (Arabies balsamea [L.] Mill.) provenances indicated that current-year needles of red spruce, but not balsam fir, were 8° to 12°C less cold tolerant than year-old needles in late autumn and early winter. (...)