This is my close to forty year old gardenia. My problem is the sweetgum tree that is growing out of the middle of it. I'm trying to figure out what I should do so that I don't lose this amazing bush.
The sweetgum can be removed, although you may need to have the tree removed professionally given the size. The remaining stump then can be immediately treated with a herbicide without hurting the gardenia. Paint the freshly cut surface of the stump with the herbicide triclopyr (Brush Killer, Brush B Gon, Cut Vine and Stump Killer and other brands). This will kill the stump and keep it from sprouting.
Consumer Horticulture Specialist
The LSU AgCenter and the LSU College of Agriculture