how to care for gardenias
I have a gardenia tree. How do I care for it (fertilizer, etc.)?
First question, what zone are you in. This article will help you figure it out: https://www.gardeningknowhow.com/planting-zones/usda-planting-zone-map.htm
Since you say your zone is "cold" I'm hoping your gardenia is potted. This article will get you started: https://www.gardeningknowhow.com/ornamental/flowers/gardenia/gardenia-plant.htm
You can keep your gardenia outside in the summer, and bring in in before the temperatures drop.