Gauging how fast a magnolia tree will grow depends on the species of magnolia and the soil and weather conditions where it is planted. In general, magnolias are flowering, warm-climate trees that thrive best in slightly acidic soil.
M. grandiflora is known as the southern magnolia or bull bay tree. It may grow up to 24 m (80 feet) in height. This long-lived tree generally grows at a slow rate of about one to two feet per year. Its growth may be hastened by the use of water and fertiliser.
M. stellata is known as star magnolia. It generally grows no more than 6 m (20 feet) tall and is used as a shrub or landscaping feature in most settings. Star magnolias are known as slow growers, often growing just 90 cm to 1.8 m (3 to 6 feet) over five or six years.
M. x soulangiana
M. x soulangiana is commonly known as saucer magnolia. It reaches a height of no more than 9 m (30 feet) with a growth rate of about 30 cm (1 foot) per year.
M. virginiana, known as sweetbay magnolia, is among the faster growing magnolias. Depending on soil and weather conditions, sweetbay magnolias grow up to 45 cm (1.5 feet) per year. At full maturity a sweetbay magnolia may reach 15 m (50 feet) in height.
M. acuminata is a hybrid known as the cucumber tree. It has a fast growth rate of up to 75 cm (2.5 feet) per year and may reach 24 m (80 feet) in height.