Why are my magnolia’s leaves and flowers wilting so quickly?

The problem is likely due to a root or soil related problem- possibly a girdling root, excess soil over the root flare, or root disease. Contact a certified arborist to insepect the tree and the site to determine potential causes of the problem. Magnolia trees in Texas are relatively free of serious pest problems that would cause these symptoms so the problem is like due to a site or condition.