The Quest for Conifers
The popularity of conifers for ornamental landscape use has increased across the U.S. in recent years (see for example Davis, 1995, and Tormey, 1999), and now most nurseries and garden centers carry select species from each of the major genera (Abies, Larix, Picea, Pinus, Pseudotsuga, and Taxodium). In the Upper Midwest, however, problems with insects, pathogens, and climatic stresses damage the best-known and most-used taxa, in some cases to the point of making them obsolete. For example, professionals in the region no longer recommend planting Scotch pine (Pinus sylvestris) or Austrian pine (Pinus nigra), due to insect and disease pressures on these species (Gleason et al., 2000). Pathogen problems also plague the popular Colorado blue spruce (Picea pungens).