Magnolias are a family of flowering trees that are among the most majestic in the plant kingdom. They produce large white, cream, pale yellow or pink blooms in spring and early summer. Magnolias are fairly heavy feeders and benefit most from a balanced, slow-release fertilizer applied at least twice and possibly three times per year.
Feed your magnolia tree beginning in the early spring, just as the tree foliage is starting to unfurl. Scatter a 10-10-10 or 8-8-8 granular slow-release formula from 12 inches out from the trunk to 12 inches past the drip line. The goal is to feed the largest roots and the widest soil footprint.
Repeat the application of slow-release fertilizer in the early summer. Make a third late summer application in warmer climates where frost and freezing temperatures are not an issue.
Water the fertilizer in deeply after every application to begin the percolation of nutrients into the soil. Mulch over the fertilizer application in spring with several inches of shredded bark, leaf mold or cocoa bean hulls to hold moisture in the soil and insulate the roots.
Refrain from fertilizing fall-planted magnolias until the following spring to prevent new growth that will be unable to harden off before or survive the winter cold.