Cold Stratification of Pacific Madrone Seeds

Abstract

Cold moist stratification for 40 d resulted in excellent (≥ 87%) germination for 11 seed lots of Pacific madrone (Arbutus menziesii Pursh. [Ericaceae]) from California, Oregon, and Washington. Without stratification, germination was < 2%. Stratification periods longer than 40 d yielded little or no gain for most lots and resulted in premature germination and development of seed coat molds. Germination after 20 d of stratification varied markedly with seed lot (from 10% to 100% of the maximum); 20-d germination was negatively correlated with latitude but not with elevation or mean winter temperature. Growers would need to test individual seed lots to determine if stratification times < 40 d would be adequate; such testing is most likely to be warranted with lots from California or southern Oregon.