Survival of coastal and interior Douglas fir seedlings after storage at different temperatures, and effectiveness of cold storage in satisfying chilling requirements

Abstract

Survival and growth of coastal and interior provenances of 2-0 Douglas fir (Pseudotsugamenziesii (Mirb.) Franco), after storage for 16 weeks at different temperatures, were examined in two experiments. In the first experiment, plants of two coastal and two interior provenances were grown under three sets of environmental conditions. These provided non-hardy, partially hardy, and hardy stock of each provenance for storage at 2, −5, and −9 °C. Survival, after 8 weeks poststorage growth in the greenhouse, showed that no provenances survived storage well in a non-hardy condition, and that coastal provenances only stored well at 2 °C. Even interior provenances did not store well at −9 °C.In the second experiment plants of four coastal and four interior provenances were lifted on 10 November and again on 8 December for storage at 2 and −2 °C. Survival and stem relative growth rate measurements, made after plants had been allowed 8 weeks poststorage growth in the greenhouse, showed that 2 °C was less deleterious than −2 °C, and that coastal provenances were less tolerant of the lower temperature. Plants stored on 10 November showed better survival than those stored on 8 December, and there was no clear relationship between stem hardiness, measured by an electrical conductivity method, and survival after storage.In a third experiment, two coastal provenances of 2-0 Douglas fir were used to compare the effect of cold storage at 2 °C with exposure of heeled-in stock to open nursery conditions in satisfying the chilling requirement for bud flushing. Flushing of previously unchilled stock, which had been cold-stored for 12 weeks, occurred as rapidly as flushing of similar stock heeled-in in the open nursery for the same period.