Effects of Provenance, Years, and Planting Location on Bud Burst of Douglas-fir

For 3 years and in two planting locations, date of bud burst was monitored on Douglas-fir saplings from 16 Pacific Northwest provenances. Provenances planted in the Willamette Valley in western Oregon differed genetically in their date of bud burst. Saplings planted in western British Columbia burst bud an average of 16 days later than in Oregon. The significant provenance x year interaction in Oregon seemed due more to a scale effect rather than to a large shifting in provenance rankings in the different years. Correlations showed that provenances originating from areas with low summer rainfall tended to have early bud burst. These field results, coupled with those of recent growth-room studies, indicate that summer drought in some areas of the Pacific Northwest may have resulted in the natural selection of seedlings with early bud burst. Forest Sci. 25:161-167.