Q.saucer magnolia
I have had my magnolia for 5 years now and although it flowers, it does not grow any taller. What do I need to help it grow?

Average growth per year on a Saucer Magnolia is 13 to 24 inches per year.
The mature height on this tree 20 to 30 feet high with a spread of 25 feet.
The soil should be moist and well draining.
Full sun is needed for a Saucer Magnolia to do well.
The age of your tree may certainly effect blooming. Some species take years to began blooming.
Check the ph level of your soil. Your tree prefers a range of 5 to 6.5
If a soil test shows a lack of nutrients, use a acid fertilizer such as Holly Tone.
https://www.gardeningknowhow.com/ornamental/trees/magnolia/saucer-magnolia-trees.htm