Magnolia trees and azaleas are very similar in the types and levels of nutrients they require, and both prefer highly acidic soils. For this reason, gardeners often can treat the plants the same with regard to feeding. A fertiliser labelled for use on azaleas can be used to fertilise magnolia trees. In addition to magnolia trees, azalea fertiliser works with holly bushes, dogwood trees and hydrangeas.
Fertilise in late spring, when the magnolia tree has finished blooming for the year. Wait until late May before applying the first fertiliser if the magnolia is a late-blooming variety.
Spread a slow-release, granular azalea fertiliser on the ground underneath the magnolia tree. Follow label instructions for application details. Extend the fertiliser outward until reaching the length of the longest tree branch.
Saturate the soil around the magnolia tree with water to help partially dissolve the fertiliser granules and soak the nutrients into the soil near the tree's roots.
Apply a second application of fertiliser in late June for all varieties of magnolia trees.
Choose an azalea fertiliser that has almost equal parts nitrogen, phosphorous and potassium for the best results.