Question
I just transplanted 6 blue spruces in my yard and they are about 8 to 9 inches in trunk size, and I'm wondering if I should fertilize these trees and if so what should I use and where to get the good stuff.  We are located in Wisconsin so should I do it when the weather warms up or when should it be done.  I don't want to lose these trees.

Answer
Most current research shows trees developing root systems faster without additional nutrients being made available. Hence, for rapid establishment of that plant part which is most needed when planted in its ultimate location, little, to no fertilizer is recommended. At the same time, water management is crucial at this point and nothing helps in this regard more than mulching. Keep away from trunk though!
I would wait a couple of growing seasons maybe even three,  before fertilizing new transplanted trees --this will give them time to establish a root system. Then use a slow release fertilizer for trees--check with your local nursery for this fertilizer.