Seed Stratification of Engelmann Spruce and Lodgepole Pine: The Effect of Stratification Duration and Timing of Surface-drying

Based on the speed and completeness of laboratory germination and nursery bed emergence, the present study showed that for both Engelmann spruce (Picea engelmannii [Parry] Engelmann) and lodgepole pine (Pinus contorta Dougl.): (1) longer stratification generally improved the rate, and in some cases completeness, of germination more so under a cool temperature (15 °C/5 °C) regime than under a warm, standard temperature (30 °C/20 °C) regime emphasizing its importance for early spring outdoor sowing under suboptimal germination temperatures, (2) for a given stratification period, surface-drying at the end of stratification was at least as effective as surface-drying prior to or during stratification, and (3) stratification periods of 6 weeks or longer were generally the most effective. A 6- to 8-week stratification with seeds surface-dried at the end of stratification is recommended for nursery sowing of both species. Key Words: stratification, pinus contorta, Picea engelmanni, laboratory germination, nursery bed emergence.