|I would like to know the difference between Magnolia|
|You're right - there are dozens of different magnolias and they seem to have all kinds of shapes, leaf sizes and colors, and sizes|
Little Gem is a dwarf Southern Magnolia with smaller dark green foliage and is very compact and narrow in form. It is ideal for smaller gardens. The leaves of this evergreen shrub or small tree are rusty-brown on the undersides. A heavy bloomer, white flowers appear early and again late in summer. Evergreen. Full sun. Moderate-growing to 20 to 25 feet high, 10 to 15 feet wide.
St. Mary is a small evergreen tree with glistening green leaves above with showy bronze coloring beneath. Compact form with dense branches creates a pyramidal shape. Early, large, cup-shaped, fragrant white flowers. Full sun. Slow-growing to 20 to 25 feet high, equal width.
The major difference are the leaf color and overall size; Little Gem will have a more upright appearance; St. Mary will have a broad canopy. I suspect you'll want St. Mary for the traditional look of a single trunk and an spreading canopy.
Best wishes with your landscape!