Mulberry trees (Morus genus) are known for their rapid growth rate, making them a popular choice for quick shade and fruit production. The speed of growth depends highly on the specific species planted and the environmental conditions provided. While some varieties grow extremely fast, others are considered moderate.
How Growth Speed Varies by Mulberry Species
The perception of the mulberry tree as a fast grower is largely driven by the White Mulberry (Morus alba). This species is the most aggressive grower and, under favorable conditions, can exhibit a growth rate of 3 to 5 feet per year in its early years. This rapid vertical extension allows a young Morus alba to quickly establish a substantial canopy.
The native Red Mulberry (Morus rubra) exhibits a slightly more moderate, though still quick, growth pattern. This North American species typically adds between 2 to 4 feet of height annually. Though it grows quickly and can reach heights of 40 to 60 feet, the Red Mulberry is generally less aggressive and less invasive than the White Mulberry.
In contrast, the Black Mulberry (Morus nigra) is the slowest grower of the three common species. This tree is favored for its large, high-quality fruit and typically grows at a pace of 1 to 3 feet per year. The controlled growth rate makes the Black Mulberry preferred for smaller residential landscapes.
Key Environmental Factors That Impact Growth Rate
A mulberry tree’s genetic potential for rapid growth is maximized when it receives the correct environmental inputs. Sunlight is a primary driver, as the trees require full sun exposure to achieve their maximum growth rate. While some species tolerate partial shade, a lack of direct sunlight significantly slows down new growth.
Water availability is important in the early years to support the tree’s rapid development. Young mulberry trees thrive best with regular watering, such as 2 to 3 gallons per week during their first year, to establish a robust root system. Although mature trees are drought-tolerant, consistent moisture is necessary to sustain high growth rates.
Soil conditions also promote fast growth, though mulberry trees are known for their adaptability. They prefer deep, fertile, well-draining soil, ideally a loamy texture with a slightly acidic to neutral pH between 5.0 and 7.0. Temperatures between 68°F and 86°F (20°C and 30°C) are optimal for vegetative growth. The plants tolerate a wide range of temperatures, making them suitable for USDA hardiness zones 4 through 9.
Managing the Implications of Rapid Growth
The fast growth of mulberry trees, particularly the Morus alba species, creates specific management challenges. The quick development of the crown necessitates regular pruning to establish a strong structural framework, especially when the trees are young. Pruning helps control the final size and shape, preventing wind damage to the fast-growing, sometimes brittle, branches.
The expansive and aggressive root system is a significant implication of the rapid growth, especially for trees planted in urban settings. White mulberry roots are known to be wide-spreading and actively seek out water sources. This aggressive behavior can lead to damage to underground infrastructure, potentially lifting sidewalks, compromising foundations, and invading sewer and drain lines.
Furthermore, the rapid growth and prolific seeding of the White Mulberry contributes to its invasive nature in many regions. Birds consume the fruit and disperse the seeds over wide areas, leading to the rapid colonization of disturbed sites and the prolific growth of volunteer seedlings. Management often involves promptly pulling young seedlings before their aggressive roots establish, as well as considering sterile or less-invasive cultivars where appropriate.