I have a magnolia but not the space for it
last year I planted a Magnolia Soulangena in the back of my garden, thinking it was a small bush. It turns out it's not -- I didn't know back then. I don't have the space for it to spread when mature, even though it will take many years, I'd rather not leave the problem for the future and try to save the plant now.
Question is, can it be grown in a container? Only other option is to give it away
This is what the RHS says about its size and spread - https://www.rhs.org.uk/plants/60020/magnolia-x-soulangeana/details-beta
Maybe you need to think about finding a decent home for it where it can grow as it wants or else you're going to have to accept the need to prune it in summer to restrict its size and spread. Have to say that the only shrub form I know is stellata and I've seen those get huge. I know of a shrubby form called figo but it's not hardy in the UK and will get as big as stellata if happy, so 7 or 8 metres across.
The only small magnolia trees I've seen are young ones, nowhere near maturity.
"We don't stop playing because we grow old; we grow old because we stop playing." - George Bernard Shaw