Plants will go to a particular size and stop.

People often ask for plants to do things that are not realistic and the commonest one is for a plant that will grow to a particular size and stop. That is understandable but sadly some people in the horticultural industry will actually tell them a particular plant will do just that. Providing such action is wholly unprofessional and reprehensible.

All plants will grow at different rates throughout their life and ultimately there growth will slow down a lot, but this can be when they are centuries old. Clearly some plants will always outgrow others but their growth is strongly influenced by the conditions they are grown in. To take an extreme example take an oak tree in open parkland and grown as a bonsai.