Sumac (Rhus) is widely recognized for its vibrant fall foliage and attractive, conical fruit clusters. While these shrubs or small trees offer ornamental value, their aggressive growth habit often leads to management challenges. The plant’s extensive, interconnected root system dictates its spread. Understanding the structure and depth of these roots is the first step in successful cultivation or control.
Primary Root Depth and Structure
The sumac root system is predominantly shallow and fibrous, designed for rapid resource absorption near the surface. The main lateral roots responsible for gathering water and nutrients are typically confined to the top 10 to 12 inches of the soil profile. This shallow placement makes the root system susceptible to disturbance but highly effective at stabilizing soil on slopes.
Primary structural roots, which anchor the main trunk, may extend deeper, often reaching 1 to 3 feet for stability. In poor, dry, or rocky soils, specialized vertical roots may explore depths up to 5 to 8 feet in search of water. However, the majority of the active root mass remains close to the surface, supporting the plant’s ability to thrive.
Lateral Spread Through Rhizomes and Suckering
Sumac’s aggressive nature is due to its reliance on rhizomes, which are modified underground stems that grow horizontally. These rhizomes possess nodes capable of sprouting new, genetically identical above-ground shoots, a process called suckering. This mechanism allows the sumac to form dense, unified thickets or clonal colonies.
These lateral rhizomes operate within the shallow zone, generally within the top 6 to 12 inches of the soil. The spread rate is significant, with runners extending outward three or more feet annually under favorable conditions. Over several years, a single sumac plant can establish a colony spanning 10 to 40 feet or more, making lateral spread the most important factor in management.
Influence of Species and Environmental Conditions
The growth pattern of the root system varies depending on the species and the local growing environment. Both Smooth Sumac (Rhus glabra) and Staghorn Sumac (Rhus typhina) are known for vigorous suckering and shallow root networks. Cultivars like ‘Tiger Eyes’ sumac are often selected for landscape use because they exhibit a reduced tendency to produce root suckers.
Environmental factors like soil quality and moisture availability also influence root dynamics. In rich, moist soil, the plant focuses on rapid, shallow lateral growth and increased suckering. Conversely, in dry, compacted, or nutrient-poor soil, the plant invests more energy into deeper, vertical anchoring roots for long-term survival, which slightly reduces the rate of lateral spread.
Strategies for Root System Control and Removal
Controlling or removing sumac requires methods that specifically target the extensive, interconnected root system. Simply cutting down the main trunk is counterproductive, as the resulting injury triggers a defensive survival response. This redirects the plant’s energy reserves to produce numerous new shoots, dramatically increasing rhizome activation and suckering.
To manage suckering, continuous mowing or cutting of new shoots can gradually deplete the root system’s stored energy reserves over multiple seasons. For permanent removal, a targeted application of a systemic herbicide to the entire root mass is necessary. This is achieved by cutting the main trunk and suckers near the ground and immediately applying a concentrated herbicide solution directly to the freshly cut stump surfaces. Placing a physical root barrier, such as a heavy-duty plastic or metal sheet, buried 18 to 24 inches deep, can also prevent the shallow rhizomes from crossing into unwanted areas.