how take care of gardenia plant

Question

The leaves are turning yellow.

Answer 1

You don't mention whether your plant is in the ground, or a container, or kept outdoors or indoors. However, here are a couple of general articles that cover a lot of conditions and might be helpful to you: https://www.gardeningknowhow.com/ornamental/flowers/gardenia/helping-a-gardenia-bush-with-yellow-leaves.htm
https://www.gardeningknowhow.com/ornamental/flowers/gardenia/gardenia-plant.htm