Gardenias that seem to have disease
I have two lovely gardenia plants that are potted. They were healthy and bloomed all summer with many fragrant blooms. I brought them in for the winter and kept them moist and placed them in indirect light. Now they have developed brown spots on the wood that resemble the back of a ladybug but not quite as large. They have also developed on the new growth and leaves a sticky substance. First I sprayed them with detergent water, but that hasn't helped. They have grown to about 4' and I desperately want to save them. Can you help with any suggestions as to how I might do this? Thank you
This sounds very much like a stem canker.
Though not as common as other disease, it can occur and the only real treatment is to remove the diseased plant material.
Depending on the severity of the disease, the plant may or may not survive.
Here are some links with more information.