I have a young plant that's on its 3rd or 4th year. For reference, I'm in the southeastern US. Very hot and humid. It grew a few short stems in the last two year. This year, the main stem grew about 20" (and counting)!!!! I'm guessing it's because in the prior years, it was getting too much sunlight and not enough water.

So my question is, should I give it a vertical support through the winter or wait until next spring? When and where should I start pruning it?

In the below image, it's about 16" high. In the last few weeks it's grown another 4".