The Sky’s Wallpaper by kubse
TheGardenLady received this question from someone whose name cannot be found.
My magnolia bush is turning yellow and then the leaves turn brown and drop off. The other leaves have black spots on them. I do not see any insects on them. Could this be a blight? And what should I do to save the bush?
There are about 80 species of magnolia. Not knowing what type of magnolia you have or where you live, my first question is whether you own a deciduous or an evergreen magnolia. If it is a magnolia bush, it may be deciduous and the thing that deciduous bushes do, is drop their leaves in the cool part of the year and regrow new leaves in the spring.  See here. So if the magnolia looks otherwise healthy, there is nothing you need do.
But if you have an evergreen magnolia, if the leaves are turning yellow you may have a problem. Is every leaf turning yellow then brown and dropping off? Or are just a few dropping off? If it is just a few, remember that even evergreen trees lose some of their leaves each year and there is nothing to worry about.
Sometimes trees are affected by environmental conditions. What has the weather been like in your area? Have you had the heat and drought conditions that we have had on the East coast of the US? This heat has affected lots of trees, shrubs and plants. No one can tell you whether these trees, shrubs and plants will survive from this excessively hot summer. Many of us are are having problems with or losing trees, shrubs and plants. Trees don’t always die right away. Trees may struggle for a few years and then die. It takes a while for a tree to give up its ghost. Excessively cold winters can also have a similar affect on the life of plants. If the cause of your tree’s leaves turning yellow is from the environment, there is little that can be done other than to try to keep the soil at its optimum level. See here.
I hope you have not over watered or under watered your magnolia. Magnolias do not like to be over watered.
Have you had your soil checked just in the area where your magnolia is growing? This GardenLady ALWAYS recommends a soil test taken in the area where you are concerned. You can get the best soil testing done by your state extension office or your Master Gardener office (Master Gardeners are part of the state extension). You will then get all the information to see if the magnolia is getting the needed nutrients and if it is not, the office will recommend how to amend the soil for the needs of the plant or plants.
If the magnolia’s leaves are a yellow or dark brown with green veins, this may indicate a severe iron deficiency often caused by an alkaline soil pH (nutritional value in soil)–a pH level of 6.5 and above. Chlorosis, is the the term used when a plant lacks iron. The soil test will tell you what your soil pH is. See here.
Also rake up all yellowed and spotted leaves under the trees and dispose of them. Just in case the leaves have a fungal infection, the removal will prevent any fungus from spreading.
And if these answers are not satisfactory, take a small branch of your tree with the yellow and brown leaves on it to your Master Gardener or Extension office for them to look at the problem under a microscope.
Please let TheGardenLady readers know how your magnolia bush is.