Sumac species, such as the aggressive Staghorn Sumac (Rhus typhina) and Smooth Sumac (Rhus glabra), are often admired for their vibrant fall color and unique pyramidal fruit clusters. However, this woody shrub is widely known for its tenacious, spreading nature, which can quickly turn a desired specimen into an unwanted thicket. Managing this aggressive spread requires a targeted approach aimed specifically at controlling and eliminating the extensive underground structure. The primary challenge for property owners is the plant’s ability to colonize large areas far beyond the original planting location.
How Sumac Roots Spread
The aggressive colonization observed in sumac plants is directly attributable to specialized underground structures called rhizomes. These horizontal stems grow laterally beneath the soil surface, acting as the plant’s primary mechanism for vegetative reproduction and expansion. As rhizomes extend outward, they possess nodes capable of generating new vertical shoots, commonly referred to as suckers, which emerge as new, genetically identical plants.
This spread is regulated by the plant’s hormonal control system, known as apical dominance. While the main stem is intact, it produces hormones that suppress the growth of latent buds on the rhizomes. When the main trunk is cut or severely damaged, this suppressive signal is removed, causing a prolific burst of suckering around the original site. Simple pruning or cutting is therefore ineffective for long-term control, as it stimulates the root system to generate dozens of new stems instead of eradicating the plant.
Non-Chemical Control Methods
For property owners seeking to manage sumac spread without chemical applications, several non-chemical methods are available.
Physical Root Barriers
Physical barriers offer a structural solution for containment. Installing a dedicated root barrier involves placing a thick, impermeable material, such as heavy-duty plastic sheeting or galvanized metal, into the soil around the desired plant or property boundary. The barrier must be buried to a depth of at least 18 to 24 inches to effectively intercept the laterally spreading rhizomes.
Proper installation requires positioning the barrier between the established sumac and the area to be protected. The material should slightly protrude above the soil line to prevent rhizomes from growing up and over the barrier. While installation requires significant labor, barriers provide a long-term physical block that forces the plant to remain contained. This method is effective for preventing colonization but does not eliminate the existing root mass.
Depletion of Energy Reserves
Another strategy involves the persistent depletion of the root system’s stored energy reserves. Although simply cutting a stem stimulates new growth, repeated, frequent cutting or mowing can eventually exhaust the entire underground structure. This approach requires weekly or bi-weekly removal of any emerging suckers during the entire growing season, year after year.
The goal is to prevent new shoots from photosynthesizing and replenishing the carbohydrate stores in the rhizomes. It often takes two to five full growing seasons of relentless cutting to significantly weaken and potentially kill the extensive root system. This technique functions as a management tool rather than a rapid eradication method.
Manual Excavation
Manual excavation provides the most immediate eradication for small, isolated patches of sumac, though it is physically demanding. Success hinges on the complete removal of the extensive rhizome network, as even small fragments left behind in the soil possess the capability to regenerate an entire new plant. The soil must be carefully sifted or turned over to ensure all pieces of the woody rhizomes are extracted from the ground. This method is generally impractical for large, well-established groves due to the sheer volume of soil and root material that must be disturbed and removed.
Using Herbicides for Root System Management
Chemical control offers the most reliable path to complete eradication of a deeply established sumac root system. Systemic herbicides are formulated to be absorbed by the plant and translocated throughout its vascular system, ultimately reaching the farthest extent of the underground rhizomes. The most commonly recommended active ingredients for woody plant control are glyphosate and triclopyr, which disrupt specific metabolic processes within the plant.
Cut-Stump Treatment
The technique known as the cut-stump treatment is significantly more effective than general spraying for woody plants like sumac. This process requires cutting the main trunk or sucker stem close to the ground, leaving a fresh, level surface. The concentrated herbicide must then be applied immediately to the exposed cambium layer, the thin, living tissue just beneath the bark.
Applying the chemical within minutes of cutting ensures maximum absorption and downward movement into the root system before the wound seals itself. This localized application minimizes the risk of chemical drifting or affecting surrounding, desirable vegetation. The concentration used for cut-stump treatment is typically much higher than for foliar applications, often around a 25 to 50 percent solution.
Timing of Application
The timing of the herbicide application is crucial to achieving full root kill. Treatment should occur in late summer or early autumn, generally from August through October, just before the plant enters dormancy. During this specific period, the sumac actively moves photosynthetic sugars and other resources downward to the roots for winter storage. This natural physiological process carries the systemic herbicide directly into the entire rhizome network, maximizing the lethal dose delivered. Applying the herbicide in the spring or early summer, when resources are moving upward to fuel new leaf growth, is far less effective for root elimination.
Foliar Spraying
Foliar spraying, which involves applying a diluted herbicide solution directly to the leaves, is an alternative method but carries notable drawbacks. While it can kill the above-ground portions of the plant, it is often less effective at delivering a killing dose to the deep and extensive root system. Furthermore, foliar applications pose a higher risk of non-target damage to nearby plants through spray drift, necessitating careful consideration of wind conditions and proximity to other garden plants. All chemical products must be applied strictly according to the manufacturer’s instructions and safety guidelines, including the use of appropriate personal protective equipment.