Magnolia trees, with their large, fragrant blooms and ancient lineage, are a captivating addition to any landscape. The genus Magnolia is one of the oldest flowering tree groups, predating bees and relying on beetles for pollination. People considering planting a magnolia often wonder about the speed at which this tree will mature. Understanding the rate of height gain is important for planning a garden and setting realistic expectations.
Defining the Typical Growth Rate
The growth rate of a tree is measured by the average vertical height it gains each year once established. Arborists categorize growth into three ranges:
- Slow growth: 12 inches or less annually.
- Moderate growth: 13 to 24 inches per year.
- Fast growth: 25 inches or more annually.
The Magnolia genus falls primarily into the slow-to-moderate category. Most varieties exhibit a moderate growth rate, adding 12 to 24 inches annually after their initial establishment phase. Young magnolias focus heavily on root development in their first few years, which makes initial above-ground growth appear slower. This investment contributes to the tree’s stability and long lifespan.
Species Variation in Growth
The specific growth speed depends heavily on the tree’s genetics. The popular evergreen Southern Magnolia (Magnolia grandiflora), known for its massive size and glossy leaves, is a slower grower. This species typically adds about 12 inches per year once established. Its growth is characterized by a slow, steady, and long-term trajectory.
In contrast, the deciduous Saucer Magnolia (Magnolia × soulangeana) shows more vigor. This hybrid, famous for its early-spring blooms, usually exhibits a moderate growth rate, often adding up to 24 inches annually under ideal conditions. This makes it a slightly better choice for a gardener seeking to see noticeable size gain sooner.
The Star Magnolia (Magnolia stellata), a smaller, shrub-like variety, is generally slower than the Saucer Magnolia. Its growth rate is closer to the slow classification, typically gaining 12 inches or less each year. Its compact nature and slower pace make it better suited for smaller garden spaces.
Environmental Factors That Influence Speed
While genetics set the potential speed, external conditions and care practices modulate the actual growth rate of any magnolia. The tree requires well-drained, slightly acidic soil, ideally with a pH range between 5.5 and 6.5. Poor drainage or alkaline soil impedes the tree’s ability to absorb necessary nutrients, which significantly slows growth.
Sunlight is important, as magnolias grow faster in full sun than in partial shade. More sunlight provides the energy needed for robust photosynthesis, directly supporting increased vertical and lateral growth. Protection from intense afternoon sun can be beneficial for certain species, especially in hotter climates.
Consistent soil moisture is important, particularly for newly planted magnolias establishing their root systems. Watering deeply and less frequently encourages the development of strong, deep roots. Applying an organic mulch around the base of the tree helps to conserve this moisture and regulate soil temperature.
The local climate and hardiness zone also play a role, with magnolias thriving best in temperate environments. Extreme cold or excessive heat stresses the tree, causing it to expend energy on survival rather than growth. Finally, an appropriate, balanced, slow-release fertilizer applied in the spring can optimize growth.