Non-flowering: Newly planted trees can take several years to settle before starting into flower. Flowering is very dependent on site, and for M. grandiflora plants in warm, sunny conditions are likely to flower best. Excess pruning can also delay flowering.
Blackened flowers or buds: Flowers and flower buds of the early spring flowering magnolias are susceptible to frost damage.
Yellow leaves: Young leaves of many magnolia are naturally pale but yellowing of more mature foliage may be caused by excessive alkalinity.
Leaf loss: Leaves of evergreen magnolias are long lasting but are shed after several years leading to harmless, if alarming, leaf fall episodes in early summer.
Watch out also for signs of bracket fungi, brown leaves, honey fungus and Phytophthora root rot.