Although there are different ways to fertilize spruce trees, This Old House recommends using a slow-release fertilizer. You will also need a small auger or an iron bar to make holes around the tree.
- Find the tree's drip line
Before you fertilize a tree, you need to find its drip line. This is where rain water drips from the outermost canopy of the tree. You will fertilize from this line and out.
- Dig holes
Using a small auger, or even an iron bar, dig small holes 12 to 18 inches deep around the drip line of the tree. Make these holes 8 to 12 inches apart.
- Mix fertilizer
Use a slow-release fertilizer and mix it with sand, compost, dirt or a combination of these. Talk to your local cooperative extension to find out what fertilizer mix is best for your area.
- Fill holes
Take the fertilizer mix and fill the holes around the drip line of the tree. Do this once a year, preferably in the fall, to keep your trees healthy.