The Mimosa tree, Albizia julibrissin, is easily recognized by its delicate fern-like foliage and abundant pink, silk-like flowers that bloom throughout the summer. This ornamental species, native to Asia, is a fast-growing, deciduous tree that was introduced to the United States for its striking aesthetic qualities. However, the tree’s rapid growth and aggressive nature are closely tied to an often problematic root system that can cause significant landscape and structural issues.
Anatomy of the Mimosa Root System
The Mimosa root structure is predominantly lateral and shallow, developing a widespread network that aggressively colonizes the top layers of soil. Rather than relying on a single, deep central taproot, the tree utilizes a mat-like system of numerous fibrous roots that extend far beyond the canopy’s drip line. This configuration allows the tree to quickly absorb surface water and nutrients, which contributes to its reputation as a fast-growing pioneer species.
The most damaging elements of the root system are often only two or three large-diameter roots that originate near the trunk and grow outward just beneath the soil surface. As these few main lateral roots expand in girth over time, they exert considerable force on any surrounding hardscape.
Potential for Structural Damage
The expansive and shallow growth pattern of the Mimosa root system leads to direct interference with nearby built structures. The expanding lateral roots can easily lift and crack concrete surfaces, damaging sidewalks, driveways, and patios. This physical pressure occurs as the roots increase in diameter over many growing seasons.
The tree’s relentless search for moisture directs its roots toward underground water sources. They often exploit minute cracks or loose joints in drain fields, septic systems, and water or sewer pipes, where they can grow rapidly and cause blockages. Homeowners should plant the Mimosa 15 to 20 feet from any permanent structure or underground utility line to mitigate these risks.
The roots can also indirectly affect shallow foundations, low retaining walls, and basement slabs by altering the soil’s moisture content. In clay-heavy soils, the roots draw significant amounts of water away from the structure during dry periods, causing the soil to shrink and leading to subsidence. This soil movement can remove support from the foundation, resulting in uneven pressure and subsequent cracking or shifting of the wall.
Managing Root Sprouts and Suckers
Mimosa root invasiveness is characterized by its strong tendency to produce numerous root suckers, or sprouts, often many feet away from the main trunk. This vegetative regeneration is a survival mechanism where dormant buds along the lateral roots are activated, especially when the main tree is stressed, injured, or cut down. The extensive, shallow root system contains a vast reservoir of stored energy, which the activated buds quickly use to produce new, rapidly growing saplings.
These sprouts are a maintenance issue because simply mowing or cutting them back only stimulates the root system to produce more growth. The disturbance triggers vegetative buds on the remaining root fragments, leading to a denser thicket of new growth. This tenacity makes the tree difficult to eradicate once established.
For effective control, the most comprehensive method involves a targeted chemical application to the cut stump or the sprouts themselves. Cutting the sprout or a small tree low to the ground and immediately applying a concentrated herbicide to the fresh cut surface ensures the chemical is transported directly into the root system. This method targets the entire root network, minimizing the activation of new dormant buds and eventually exhausting the tree’s capacity to send up new sprouts.