Fertilizer spikes are compressed rods of fertilizer that are driven into the ground around trees to provide nutrients to the soils. They break down slowly, releasing a steady supply of nutrients. They are more expensive than granular fertilizers but are also more convenient to use. Spike varieties are made for general tree use, or there are types specially formulated for the specific type of tree. Using fertilizer spikes correctly is key to getting the proper amount of nutrients to the trees roots in a usable form.
Push the plastic cap, included with the tree spikes, onto the blunt end of the spike. Plastic caps are reusable so there are more spikes than caps in each package.
Set the point of a spike into the ground at the distance from the trunk recommended on the fertilizer spike packaging. Drive the spike into the ground using a rubber mallet until the plastic cap is just above the soil level.
Pull the plastic cap off the spike. Finish driving the spike into the soil until it sits 2 to 4 inches beneath the soil surface.
Place the cap on a second spike and drive it into the soil. Use the amount of spikes recommended on the package for your tree type and size, spacing them equally apart around the tree.
Water the tree thoroughly after installing the spikes. The spikes will slowly dissolve in the soil and leach the nutrients to the tree roots. Replace them as recommended on the spike package.