Trees of subalpine fir may begin to produce cones when 20 years old, but under closed-forest conditions, seed production is not significant until trees are older. Corkbark fir does not begin to bear cones until about 50 years old. Maximum seed production occurs in dominant trees 150-200 years old.
Germination and early survival are generally best on exposed mineral soil and moist humus, but a wide variety of other seedbed types also provide adequate conditions. Spring planting is most successful. Subalpine fir invades and establishes on open, severe or disturbed sites near timberline because of its ability to establish a root system under conditions too severe for its less hardy associates and its ability to reproduce by layering.
Subalpine fir is relatively slow growing. Seedlings average less than 38 cm in height after 15 years in the open. Heart rot is a severe problem, and many trees die or are complete culls at an early age. Of those reaching maturity, trees 25-51 cm in diameter are often 150-200 years old, and trees older than 250 years are not uncommon. Some trees in Olympic National Park, Washington, have been determined to be over 400 years old (by ring count).
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