I purchased 12 dipladenia plants… they are beautiful! Do they lose their blooms & leaves in the fall? I live in Portland Oregon.
I realize that I must move them indoors over the winter. I will move them into my garage and provide lighting.
Certified GKH Gardening Expert
They are not hardy in your area. Dipladenia should not lose their leaves, as they are an evergreen. This will mean that they have gotten a little too cold. Sometimes they can recover, but they don't tolerate the cold well.
The best thing from here will be to slow WAY down on care, watering, and anything that you do to it at all until it recovers. Trying to help it once it is stressed to this point will usually kill it, but letting it recover without messing with it much will be the best way to let it recover.
This article will help you with the care of these indoors: https://www.gardeningknowhow.com/ornamental/vines/mandevilla/growing-a-dipladenia.htm