Need some help on how to help my plant

[Sergiasiarez]

I planted my gardenia in a place that wasn’t draining well. Now her roots look half dead half alive

. I think it’s root rot

 

[Tetters]

Welcome to the forums @Sergiasiarez . Once a plant has root rot like that you may as well throw it away. Before planting any plant in the garden you need to check that the soil is right for it. If it is too wet and doesn't drain well try adding organic matter and grit to help.
Alternatively, if that area is very wet all the time, consider growing stuff that enjoys a boggy site and you will be on a winner