
Frost-blackened flowers and buds are an annual cosmetic event, not decline; the tree leafs out normally afterward. Real decline is thin undersized leaves, early yellowing, dieback progressing from branch tips inward, and on the undersides of twigs the shiny wax-covered bumps of magnolia scale — the largest scale insect in North America at up to half an inch — with black sooty mold on the foliage below. Sunscald cracking on the southwest face of the thin smooth grey trunk is the other quiet killer here, and unlike scale it is not treatable.
In central Indiana this means the deciduous spring-flowering magnolias, not the evergreen southern magnolia — and the defining fact is that it blooms before it leafs out, so a normal Indiana late freeze turns the entire display to brown mush overnight in many springs. The other thing that puts one on a quote is magnolia scale, which drips honeydew onto cars, decks, and driveways all summer long.