Blue Spruce, I assume you mean Colorado Spruce. They do best in Colorado where the air is drier than Minnesota. Colorado Spruce do not do well in our humidity unless they are single trees with a lot of space between each tree to provide a lot of air circulation. The lower branches are not the problem. It is succeptability to needle cast diseases. I personally think that pruning or cutting off the lower branches spoils the look of the tree. There are other conifers with a blue toned needle that survive better in MN. Concolor Fir is one.