My Almost 2 Year Old Passion Flower Is Starting To Lose Leaves

Question

I live in San Diego, CA. and planted a passion flower vine in the ground with a trellis, with good morning sun exposure to the south. It has now grown up the trellis, over the fence, and onto and over my gateway arch. It flowered well last year, and last month (Sept – Oct) it bloomed, and now has a few fruits. The problem is the leaves on the south side of the plant are turning yellow then brown and falling off, and some of the branches are dying. It has not (yet) affected the north facing side.

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Answer 1

There could be more than one problem here. Look first for spider mites, which become active during hot weather and may explain the prevalence of the problem on the south side. There are other concerns, as well, such as a fungus or developing root rot, but the rest of the plant looks great.
Here are two articles that will help you narrow down the possibilities:
https://www.gardeningknowhow.com/ornamental/vines/passion-flower/passion-vine-dropping-leaves.htm
https://www.gardeningknowhow.com/ornamental/vines/passion-flower/fix-yellowing-passion-vines.htm