Growth and cold hardiness of container-grown Douglas-fir, noble fir, and Sitka spruce seedlings in simulated greenhouse regimes

Abstract

Seedlings of Pseudotsugamenziesii (Mirb.) Franco, Abiesprocera Rehd., and Piceasitchensis (Bong.) Carr. were grown for 5 months in growth rooms which simulated hot, warm, or cool growing regimes in greenhouses in western Oregon. Temperature, humidity, light intensity, and photoperiod were changed diurnally and seasonally. In all three species, maximum heights of seedlings were attained in the hot regime, whereas stem diameters were similar under the hot and warm regimes. Dry weight increment was greatest in the warm regime. The cool regime was suboptimal for all aspects of growth. Seedlings grown in the hot regime were least resistant to cold in early fall. Differences in resistance to cold of seedlings grown in the warm and cool regimes varied by species and type of damage.