I have a 4-year old 'Green Back' magnolia (underside of leaves are bronze and then turn green with age). I have never had a flower on the tree, though it is 12-feet tall. It gets full sun most of the day until the late afternoon. It grows approx. 2 foot every year, so growing isn't a problem. I do use grey water from my washing machine on the garden in summer to help with the watering. Can you give me some suggestions as to why it hasn't flowered?
Magnolia Not Flowering
It sounds like it could be any of four things.. Most of the large growing southern magnolias won't bloom until they have some age on them. It is common for young plants to be 8-10 years old before having a lot of blooms.
You might consider having the soil tested. Magnolias prefer an acidic soil, and you can easily alter the pH if needed.
It could be the type fertilizer you are using. Too much nitrogen can cause a plant to put out foliage instead of blooms.
AND, the greywater could be too alkaline. Greywater containing sodium, bleach or borax can damage plants.