Southern magnolia trees in the wild bloom much more abundantly than domesticated samples. Many horticulturalists believe this is due to the constant supply of magnolia leaf and flower litter that provides wild magnolias with the nutrients they need to produce bloom after bloom. To encourage your domestic southern magnolia to bloom with the vigor of its wild counterparts, give it a little help with a consistently applied fertilizer.
Wait until a newly planted southern magnolia is established and producing new growth before fertilizing out.
Measure an area that is roughly three times the area of your southern magnolia tree's canopy spread. Mark the area off with twigs or rocks.
Water the demarcated area deeply so the soil is moist to roughly the depth of the root ball.
Measure the appropriate amount of fertilizer. To ascertain the square footage, measure the length from the trunk of the tree to the edge of the circle you marked off in feet. Then square this number and multiply it by pi (approximately 3.14). This will give you the square footage of your fertilizing area. You will need two cups of fertilizer per 100 square feet of fertilizing area.
Spread the fertilizer evenly over the area you have marked off.
Water the area again until all of the fertilizer has soaked into the soil.