We have a Monrovia Black Tulip Magnolia, now about 5 years old. The first couple of years it bloomed as promised. More recently it has started to bloom in the late summer/ fall as well as the spring. Most of the blossoms tend to be deformed in some way. The tree is also suffering from die back of die back of new growth on some branches. Can I do anything to bring it around or should I just cut it down?
Magnolia × soulangeana ‘Black Tulip’, is best grown in moist, well-drained, preferably acidic to neutral soil in sun or partial shade. It is not uncommon for magnolias to bloom more than once, although usually the second flush puts on less of a show. You described your blossoms as being deformed in some way which made me question whether or not something was eating the bud? Have you noticed any insects or critters on your tree? If you have not already, I would suggest having a close look at the buds, branches and emerging leaves to see if there is any sign of pest activity.
With regards to the new branch dieback, this could be caused by a number of things. When the branch dies back, are the leaves blackened? If so, this could be a scale infestation and contacting a certified arborist or tree care company would be recommended. Is the branch dieback occurring primarily on one side? This could be caused by a soil borne pathogen called Verticillium wilt. It usually occurs when the tree has been stressed in some way, due to stressed roots, wounds or prolonged drought. The fungus can survive in the soil for a number of years so if you do choose to replace your tree with another specimen it would be wise to choose one that is not affected by this condition. For a list of these, please see the following link: https://depts.washington.edu/hortlib/resources/ucdavis_verticillium.pdf
For further information on how to care for your magnolia, please see a previous post from our website with a list of tips to help your tree recover from trauma and stress: https://www.torontomastergardeners.ca/askagardener/magnolia-bud-drop/