fertilizing a blue spruce
If you fertiize your lawn, and the spruce is located in the lawn area, then no fertilization should be necessary for the spruce. Healthy, mature trees do not usually benefit from fertilization. Trees in the landscape receive nutrients from turf fertilization, grass clippings, fallen leaves and natural soil fertility. Do not overfertilize as this can encourage sucking insects and weak succulent growth.
Best time to fertilize your lawn is in the fall. If you have not had your soil tested in the last 3 years you can do this now. http://extension.umd.edu/hgic/soils/soil-testing
Here is our link on fertilizing and the fertilizer schedule http://extension.umd.edu/hgic/plants/fertilizing-lawns