red mandevilla vine
Got my red mandevilla vine about 1 1/2 years ago. It was fairly bushy when I brought it home, and flowering. It very quickly dropped leaves on the woody parts but put out lots of long leggy vines, which I trained onto the trellis I had put around it. In doing this I discovered a severe aphid infestation, and then whiteflies, which I treated by squishing regularly, clipping off infested growth, and finally two timed applications of neem and safer soap. The lower woody vines became so bare that I chopped off the vines to about 2/3, and in some cases 1/2. It seemed to do well for a time; it flowered and began to bush out. The blooms have dropped by now, and it experienced another severe leaf drop. I'm considering chopping it back again, but do do so will leave it nearly leafless as growth is concentrated in the branch ends, with leaf drop in the older growth. It is in a 12 inch pot in a sunny SW window of my heated sunroom.
Certified GKH Gardening Expert
I have found an article for you that will explain how to correctly prune this: https://www.gardeningknowhow.com/ornamental/vines/mandevilla/prune-mandevilla-vines.htm