They grow very fast, and they can be large, brittle trees with shallow roots. I understand they can be grown as a bush, but I haven’t seen that.

They prefer to be in the ground but you can keep them in a pot, a very large pot. In the ground it can get over 20 ft tall. It takes well to trimming so do worry to much if you are heavy handed cutting it back.

I got one in a small pot a few years ago, and planted it close to the house, thinking 'well, the winter will freeze it to the ground'. By mid-summer the thing was over 8 feet tall, and I was like OMG I need to move this sucker. I butchered the root system moving it, but the thing barely even noticed. I stuck it out in the yard, and it has kind stopped growing at about 15'. The leaves and flowers are very sparse - I don't know if it is a nematode thing or what, but I also seem to have no issues with winter dieback.

Not sure if that helps, but I would put it somewhere it can stretch out.