My gardenia has yellow leaves. Buds come on the tree, then turn. No flowers in two years. Put mulch around the tree to keep it moist. I'm in southern TX.
Certified GKH Gardening Expert
The yellow leaves mean that the plant is under a kind of stress and, when it is stressed, it can't hold on to its flower buds. This article will help you pinpoint the problem: https://www.gardeningknowhow.com/ornamental/flowers/gardenia/helping-a-gardenia-bush-with-yellow-leaves.htm