Southern Magnolia Leaf Drop

Algal Leaf Spot

     Chicken Little is wrong again.  The sky is not falling; it is only magnolia leaves!  Every spring, people call expressing concern about leaf drop of their Southern magnolias.  Magnolias will begin dropping leaves in November and continue until early spring.  The degree of leaf drop depends upon genetic as well as physiological factors affecting the tree. Most of the leaves are old leaves and it is their turn to fall off.  The older leaves turn uniformly yellow suddenly throughout the entire plant before dropping.  New growth at the tips of the branches is often evident at this time. Once the yellow leaves drop off, no further yellowing or leaf drop occurs until next spring.

     Most Southern magnolia trees are grown from seed, and they exhibit a great deal of variability in leaf shedding since each tree is slightly different.  Some trees may become completely bare before new foliage comes out.  When trees are propagated by grafting or from cuttings, all trees will have about the same amount of leaf drop since they are clones.

Regardless of propagation method, the degree of leaf drop can also be associated with environmental conditions.  An extremely cold winter or a dry spring can result in accelerated or additional leaf drop.  Large trees with root systems restricted by to sidewalks or planting islands may drop more leaves since their restricted root system are not as able to supply the tree with water and nutrients during periods of stress.

This spring has been wetter and warmer than usual and this resulted in a increase in algal leaf spot.  This also causes increased defoliation.  Best control is to clean up and destroy diseased leaves.

You might want to apply 4 cups per 100 square feet of 13-13-13 or similar fertilizer to give them a little boost this year.