Mulberry trees (\(Morus\) genus) are widely cultivated for their fast growth and abundant fruit production. Their ultimate size is not fixed but is determined by genetics and environment. The species and cultivar establish the genetic potential, while local growing conditions dictate how much of that potential is realized. Understanding these factors is necessary to manage a mulberry tree effectively in a garden or landscape setting.
Size Variation by Species and Cultivar
The mature size of a mulberry tree is primarily dictated by its species and whether it is a standard or a specialized cultivar. The three most common species exhibit distinct size ranges that must be considered before planting.
The Red Mulberry (\(Morus rubra\)), native to North America, is the largest species, typically reaching a mature height of 30 to 50 feet with a canopy spread of 25 to 40 feet. Exceptional specimens can exceed 70 feet tall, showcasing its potential as a large shade tree. The White Mulberry (\(Morus alba\)) is known for its variability and aggressive growth, commonly maturing between 30 and 60 feet tall with a similar canopy spread.
The Black Mulberry (\(Morus nigra\)) is a smaller, more bush-like tree that generally grows to a height of 30 to 40 feet with a wide, spreading canopy of 35 to 50 feet. It has a significantly slower growth rate compared to the other two species. Specialized cultivars are often preferred for size control. For example, the Weeping White Mulberry (\(M. alba\) ‘Pendula’) is grafted onto a rootstock, restricting it to 6 to 15 feet tall with a spread of 8 to 15 feet. Dwarf varieties, like the ‘Dwarf Everbearing,’ typically grow only 4 to 15 feet tall, making them ideal for container planting or small garden spaces.
Growth Rate and Mature Dimensions
Mulberry trees are classified as fast-growing, making them popular choices for quick shade and fruit production. The White Mulberry (\(M. alba\)) is the most vigorous, often adding 3 to 5 feet of vertical growth annually in its youth. Red Mulberry (\(M. rubra\)) also grows rapidly, typically gaining 2 to 4 feet per year.
This rapid growth phase means that standard mulberry trees can reach half their maximum height, or about 20 to 30 feet, within five years under optimal conditions. They typically reach their near-maximum mature height within 10 to 15 years, which is significantly faster than many other fruit trees.
True maturity, where the tree’s dimensions stabilize, can take 20 to 50 years, especially for the slower-growing Black Mulberry. The fast early growth is primarily vertical, but as the tree ages, its energy shifts toward lateral growth, resulting in the expansive canopy spread that defines the tree’s practical space requirement. The final mature dimensions are a combination of this early vertical speed and the later, slower lateral expansion.
Influence of Environmental Conditions
A mulberry tree’s actual size in a specific landscape is often less than its genetic maximum due to environmental limitations. The quality of the soil plays a large role; rich, deep, and well-drained soil provides the necessary nutrients and anchorage for maximum growth. Poor or compacted soil will result in a smaller, less vigorous tree.
Water availability is another limiting factor. While mulberries tolerate drought once established, consistent moisture during the growing season promotes the highest annual growth rate. Trees planted in full sun will grow significantly larger than those in partial shade, where reduced light limits the energy available for biomass creation.
The physical planting location also imposes restrictions, especially on the root system. Mulberries have aggressive, shallow root systems that seek out water and nutrients, sometimes causing damage to nearby structures. Restricted root space, such as planting near a foundation or in a small urban cutout, limits the tree’s ability to absorb resources. This acts as a natural dwarfing mechanism, preventing the tree from reaching its full potential size.
Controlling the Tree’s Final Size
For homeowners who want the benefits of a mulberry tree without its massive size, choosing a specific cultivar is the easiest control method. Cultivars like ‘Dwarf Everbearing’ or the weeping forms are naturally predisposed to remain small, often topping out at under 15 feet. These varieties require minimal intervention to stay at a manageable size for fruit harvesting or small gardens.
Aggressive pruning techniques are the primary way to manage the size of standard, fast-growing mulberry trees. Pollarding involves making an initial severe heading cut to establish a permanent height. All new growth is then cut back to the same point annually during the dormant season. This creates a distinctive, knobbed structure and maintains the tree at a fixed, modest height, such as 6 to 10 feet.
Coppicing is a similar technique where the tree is cut back nearly to the ground, stimulating the tree to produce numerous new shoots from the stump. While this is primarily used for biomass production, regular coppicing prevents the tree from forming a large trunk and keeps it in a continuous state of juvenile, shrub-like growth. Selective heading cuts, where branches are cut back to an outward-facing bud, are used to direct and reduce the spread of the canopy, keeping fruit within easy reach. These intensive pruning methods must be started when the tree is young and maintained consistently to be effective in controlling the tree’s overall dimensions.