|What is the cause of the edges of the leaves on the upper branches
of the Mystery Gardenia turn Rust colored. It has gone through the summer O.K but now it looks sad.
|What you describe is probably weather related. It's not too unusual for gardenia leaves to take on a reddish cast on the upper surfaces, and around the edges, especially on the most exposed leaves. This is generally weather-related, often because of cool nighttime temperatures or a result of hot summer sun. These leaves will eventually drop and be replaced with healthy new leaves.
Best wishes with your garden!