Large trees with complex crowns support more biodiversity than small and simple trees, and forest management in the USA is increasingly promoting large trees and variable tree densities. To inform how large trees develop in variable forest densities, we climbed and three-dimensionally mapped 36 Picea sitchensis trees 55 to 91 m tall and 70 to 250 cm diameter from the complete range of tree densities to quantify tree allometry and habitat-related appendages. Sampled trees were aged with increment cores to construct a chronosequence of crown development (100-400 years), and all trees within 30 m of each were stem-mapped to quantify forest density. Trunk and appendage diameters as well as crown volume decrease by roughly 20% for each 25% increase in forest density given tree age. Reduced growth and higher mortality of lower-crown appendages in dense forests delays development of large (>15 cm diameter) appendages for over 100 years. Presence and abundance of secondary trunks are unrelated to neighborhood density but increase with crown damage. These findings are compared to Pseudotsuga menziesii—another well-studied tall conifer. Picea develops habitat-related crown structure much faster than Pseudotsuga, yet has roughly half the longevity, indicating that these species have complementary ecological functions.