Dormancy of yellow cedar (Chamaecyparis nootkatensis [D. Don] Spach) seeds is effectively terminated by treatment with 1-propanol or nitrate in combination with a warm water soak, gibberellin and moist chilling.

Following dispersal from the parent tree, seeds of yellow cedar (Chamaecyparis nootkatensis [D. Don] Spach) exhibit a low capacity for germination as a result of coat-imposed dormancy. Germination of the mature (intact) seed requires several months of moist chilling; however, even after prolonged moist chilling, germination is typically sporadic and nonsynchronous. Here we investigate the effectiveness of chemical treatments in reducing the requirement for moist chilling. The most effective agent in this regard was the anaesthetic 1-propanol, which promoted 75-85% germination of yellow cedar seeds, when combined with a two day GA 3 treatment and 30 days of moist chilling. The promotive effect of 1-propanol was specific; 2-propanol and 1-pentanol were ineffective. In the absence of propanol, nitrate in the form of KNO 3 , along with GA 3 , was effective for dormancy alleviation when appropriate conditions were used. Soaking of seeds in warm running water (30 or 40°C instead of 21°C) before chemically treating them resulted in a further improvement in germination percentage. Moist chilling of seeds after chemical treatment was essential for improving overall germination performance and post-germination performance (i.e. seedling emergence). The duration of the traditional dormancy-breaking treatment for yellow cedar seed (87 days), could be reduced to 36 days without a compromise in percentage or rate of germination, by combining a three day soak in running water at 30°C, a one day 1-propanol treatment, two days of GA 3 and 30 days of moist chilling.