Seed Source Lifting Windows Improve Plantation Establishment of Pacific Slope Douglas-Fir

Abstract

Located on California’s north coast, the Humboldt Nursery grows bareroot seedlings of Douglas-fir for spring planting in coastal and interior regions of Oregon and California. Both survival and growth of the plantings strongly depend on when the seedlings are lifted from the nursery beds and put in cold storage. Appropriate times to lift were determined from the field performances of 33,000 seedlings of 51 seed sources, lifted on different dates and stored for varying periods. Depending on seed source, the lifting window ranged from 7 to 18 weeks in early November to late March. The window tended to widen as source latitude and elevation increased, but not for all regions. Differences among sources from the same region were common. Repeated tests of diverse sources have shown the windows are stable. Seven of 10 sources have windows of 3 to 4 months, enabling the nursery to confine lifting to times when soil and weather conditions are optimum and to schedule lifting around sources with narrow windows. Performances for seedlings lifted outside their windows are mostly poor and often preclude successful plantation establishment.