The enormous and rugged spruce tree is popular for its size, beauty and ability to withstand a variety of environmental conditions. As the Montana State University Extension points out, it can withstand extreme cold and is moderately drought-tolerant. Although spruce trees require little special fertilization care, correctly providing fertilizer can help solve and prevent some problems.
While advice about fertilizing new spruce plantings is mixed, the consensus tends toward avoiding fertilizer until the planting has a chance to establish. The University of Missouri Extension indicates that fertilizer may damage the roots of young spruce trees. Ron Smith, a horticulturalist with the North Dakota State University Extension, also discourages fertilizing new spruces.
After your tree has been established for a year, you can assess the need for fertilizer. According to the University of Missouri Extension, most evergreen trees do not require fertilizer to remain healthy. However, if your tree shows detrimental effects from poor soil conditions, disease or insect pests, you may find fertilizer helps to restore its vigor. Keep in mind as well that fertilizers tend to promote rapid growth in spruce, a tree with the capacity to become very large without any help from fertilizers. The University of Wisconsin Extension recommends curbing fertilizer use as trees begin to grow large.
Spruce trees should be dark green in color and grow steadily. If your tree shows stunted growth, pale coloration or dead or undersized needles, you may need to apply fertilizer. A soil test, available from your local extension office, can identify any nutritional deficits and recommend a fertilization program for your spruce, if needed.
Well-rotted manure provides extra nutrients for established spruce trees, either dressed around the tree as mulch or worked into the top layer of soil. If you are providing a synthetic fertilizer, your choice should be informed by a soil test to address the precise nutritional needs of your tree.
Spruce trees develop root systems that extend well beyond their canopy, and you'll want to provide fertilizer over the entire root zone. Apply fertilizer around the tree in a diameter one and a half times the diameter of the canopy. To ensure that nutrients reach the roots, use a liquid fertilizer or water in solids after application.
Trees absorb nutrients from the soil with their water, so you'll want to provide fertilizer at a time when trees are actively absorbing water. The Montana State University Extension Service recommends fertilizing spruce trees during spring, after the ground thaws and water begins moving again in the soil.