Colorado fir is not very long lived but forms a strong broad crown. When small, it is a beautiful tree but only maintains its beauty in full light. In forest shade it soon deteriorates, as have all the early plantations established by the founder of the Arboretum, A. F. Tigerstedt. What is more, most of the Colorado firs at Mustila seem to be susceptible to some kind of disease, to which only a few individuals have resistance. The best specimens grow in Pähkinärinne (or Hazelnut slope) and are mostly self-germinated descendants of older trees.