Stratification of Bitterbrush Seeds

Abstract

The influence of temperature and moisture availability during stratification on the subsequent germination of bitterbrush (Purshia tridentata) seeds was investigated. The threshold for adequate stratification temperatures was abrupt. Temperatures above 5 degrees C were too warm and below 0 degrees C, too cold for stratification; 2 degrees C was optimum for the longest duration. Prolonged stratification resulted in decreased viability, apparently from microbial activity and early germination. Stratification in osmotic solutions produced with polyethylene glycol was totally ineffective. Soil water stress reduced the effectiveness of stratification, especially with sand as a substrate. Any departure from optimum temperature and moisture regimes prolonged the time required for stratification or negated any effect of the stratification treatment.