Rocky Mountain white fir is easily recognizable by its relatively broad crown of steely-blue leaves. Seed size is variable. In the mixed conifer forests of the California peninsular and transverse ranges, white fir was, in the past, a common member of the understory. White fir is more shade-tolerant than pine or oak, and has done well in these closed canopy forests. White fir is a timber species, therefore most studies of this species have silvicultural interests in mind.
White fir is susceptible to several pathogens.
The beetle inoculates fir with the fungus, which appears to help the beetle by making the tree weaker. Fir engravers rarely attack trees with stem dbh smaller than 10 cm. Infection by these pathogens typically occurs after the weakening of trees by dwarf mistletoe. This parasitic plant grows in clumps among fir boughs. Simeone et al.