What fertilizer should I be using for a presently blooming, beautiful star magnolia? When should I be using it?
Star magnolia (Magnolia stellate) is a lovely large shrub or small tree. Michael Dirr, well-known shrub and tree expert, says he’s “never observed a bad one.”
It sounds as if your tree is doing beautifully, and getting all the nutrients it needs, so it is unlikely that it needs fertilizer. Magnolias prefer acidic to neutral soil that is moist but well-drained. It also needs a soil that is rich in organic matter. Probably the best thing you can do for it is to mix some compost into the soil around it and spread a three-inch layer of mulch around the trunk of the tree, leaving about six inches between the mulch and the trunk. Although many kinds of mulch would work, pine bark and needles are optimum because of their acidity, which the magnolias prefer. Spring — right now — is the time to do it.