Hi
That's a tough call much depends on location. naturally.
If left on their own they will clump and offset if removed they will form trunks BUT requires a long time to do so.
Mine covered about a 6 foot circle which took around 10 years it topped out at around 15 feet. i now maintain it as one clump with offsets removed and it is starting to form a trunk. I'm going to keep it under 5 feet in diameter.
I have seen clumps well over 20 feet in diameter have no idea how long it took to get to that size
It is possible to maintain them at many different sizes though good luck gary

Thank you for that, I love the look of it and wanted to make sure I could let get going without cramping its' style too much in the early years. I will take your advice too, when it gets too big and remove the outer ones (thinking positively here!)

Have a look at this web site, very good info. www.sayers-strelitzia.co.au

sorry www.sayers-strelitzia.com.au they are in Australia but very good.