Spruce trees, known botanically as Picea, are evergreens with scaled trunk bark, short matte needle foliage and seed cones in the fall and winter. Evergreens, like spruce, benefit from biennial or quadrennial applications of a complete fertilizer made in the late spring or early summer. Always apply fertilizer over deeply moist soil by watering your spruce well on at least a monthly basis when there has not been natural rainfall to irrigate the tree.
Fertilize your spruce tree in the spring after the ground has thawed and the soil can easily be worked. Fertilize up until early July but no later in order to prevent tender growth in the fall that may not stand up to winter temperatures.
Scatter a complete fertilizer with a guaranteed analysis of 10-8- 6 over the surface of the soil around the tree. Start at least a foot out from the trunk in a wide doughnut shape extending at least a foot beyond the drip line of the tree. Apply the dose recommended on the product label for the size and age of your spruce tree but do not exceed 2 lbs. of fertilizer for every 500 square feet of soil area.
Settle the fertilizer grains in to the top few inches of soil with a rake or cultivating fork, evenly distributing them in the soil around the tree.
Water the soil deeply after applying fertilizer, ensuring that the soil is wet to a depth of at least 12 inches over the entire root area in which you laid down the fertilizer.