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10-15% @ < 0°C
10 (8-12) weeks warm (c. 15°C) plus
12 (12-16) weeks cold (c. 4°C)
Only partially effective even with the longest pretreatment durations and/or several pretreatment cyclesApproximate date to initiate artificial pre-treatment (for 1 March sowing) 27 September
Orthodox – seeds that can be dried without harm, and once dried can be frozen, stored for years with little deterioration and relatively easily revived.
Figures in brackets indicate that different seedlots often require different pretreatment durations. There are three potential courses of action:
Raising Trees and Shrubs from Seed (PDF-648K)
Forestry Commission Practice Guide 18.
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