Stock-testing facilities need a fast, reliable method to estimate overwinter storability of seedlings (ability to survive and grow after cold storage). We compared two methods using container-grown seedlings of coastal and interior Douglas-fir, interior spruce, lodgepole pine, and western larch from British Columbia nurseries.
- Fall frost hardiness was estimated using visible injury of foliage or stems (VI) and chlorophyll fluorescence of shoots (CF) after freezing to -18°C. Seedlings were then put into overwinter cold storage (-2°C).
- In spring, seedlings were planted in nursery beds; survival and growth assessed after one growing season.
- There were close correlations (r >= 0.93) between VI and CF.
- Seedlings lifted after reaching >= 69% for CF and <= 25% for VI had over 90% survival at harvest and doubled shoot dry weight compared with seedlings lifted earlier.
- Measuring CF was the fastest and most easily replicated method to estimate successful storability, and reduced testing time by 6 days relative to VI tests.
After cold storage, conifer seedlings in British Columbia are tested for field growth potential before planting. We compared two tests of performance potential using container-grown conifer seedlings.
- Thawed seedlings were assessed for root growth potential (RGP) and CF.
- Seedlings were planted in nursery beds; survival and growth were assessed after one growing season.
- Performance tests were significantly correlated with each other (r >= 0.53).
- The best performance predictor was CF + RGP (R2 = 0.79 for 78 seedlot x lift-date combinations), which minimized the risk of planting poor seedlings and not planting good seedlings.
- A sum of 83 for CF + RGP provided a threshold above which survival and growth were good.
- We recommend a combination of CF + RGP to assess vigour of shoot and root systems before planting.
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Updated July 24, 2015