Any plant can be trimmed. Yes. But....home owners seem to somehow forget to trim them. All you have to do is drive down any street where the dwellings are 10+ years old to see what I'm talkin about. Also, plants are like kids. You cut their hair, but the kids keep growing! Same goes for plants, you can shear them all you want....but the branches and limbs continue to grow You have to use FORESIGHT when planting! I'd say that 3 times a week I have clients ask us to do things that sound good, but based on experience - I know it's not a good idea, or that it's out of sequence of the principles of architecture. This is when it becomes our duty as competent professionals to educate the client.