Ann Magnolia seems to be the smallest currently, however it is still going to grow taller beyond 6x6, but from what I have read the emphasis is that these are slow growing. Pink purple flowers.

Size discrepancies: one source say 8-10Ft and the other says 10-12ft.

http://www.monrovia.com/plant-catalog/plants/2464/ann-magnolia/

http://www.missouribotanicalgarden.org/PlantFinder/PlantFinderDetails.aspx?kempercode=d422

Lily Magnolia's (Magnolia Liliflora) that grow as compact shrubs and can be pruned into tree form, so maybe they can be kept at 6 Ft ( not sure?) they are hardy for zone 5- Al's Dwarf, Mini Mouse, and O'Neill.

I do not have personal experience with them...just information that I have read.

Thank you once again, angieg1.

Great information!!!

Thank You