Seed production in grand fir is relatively low. A good cone crop is considered to be more than 40 cones per tree – the interval between good seed crops is about 2-3 years. Seed production begins at about 20 years of age. Germination is best on mineral soil but in open sites the seeds germinate nearly as well on duff as on any other surface. Primary causes of germination failure are insect infestation and the perishable nature of the seeds. Grand fir seedlings are relatively resistant to drought on areas exposed to full sun because deep initial root penetration protects them from drying of the surface soil. On heavily shaded, cool areas, surface dryness from drought is the most important physical cause of seedling mortality because initial root penetration is slow.
Initial survival and growth of grand fir are favored by moderate shade, where growth may be aggressive enough to form a dominant part of the forest. After 20-30 years, it makes most rapid growth in the open. Trees 250 years old are common and occasional trees may be more than 300 years old.
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