I have two gardenia plants, one is a tree and the other a bush. They both are doing well as far as growing. However, the tree has a white powdery residue on the leaves. Both have multiple buds but they do not bloom. I live in Michigan. The plants were outside during the summer, but they have been brought into the house now because of possible frost. Any help you can give me would be appreciated.
White Residue on Leaves of Gardenia
Certified GKH Gardening Expert
The white residue is powdery mildew. Here is more information: https://www.gardeningknowhow.com/plant-problems/disease/get-the-cure-for-powdery-mildew.htm
As for the blooming, the following articles should be of some help to you: