Sumac (genus Rhus) is a woody plant known for its colorful fall foliage but also for its aggressive, thicket-forming growth habit. Once established, species like Smooth Sumac (Rhus glabra) and Staghorn Sumac (Rhus typhina) can rapidly colonize large areas, making management difficult. The plant’s capacity to spread quickly and resprout vigorously means that simply cutting the stems is ineffective for permanent removal. Successful eradication depends on understanding the plant’s unique biology and timing the treatment to coincide with a specific physiological process.
Identifying Sumac Varieties and Understanding Root Systems
The first step in any control effort is correctly identifying the species of sumac being targeted. Most eradication efforts focus on non-poisonous varieties like Staghorn and Smooth Sumac, which are common thicket-forming nuisances. These species are part of the Rhus genus and produce dense clusters of red berries when ripe. It is important to distinguish these from Poison Sumac (Toxicodendron vernix), which produces white berries and contains the irritating oil urushiol.
The challenge in eliminating common sumac lies in its extensive root system. Sumac plants form large, interconnected colonies through shallow, horizontal underground stems known as rhizomes. These rhizomes produce numerous new sprouts, or suckers, often many feet away from the parent plant. Cutting the above-ground stem often stimulates these dormant buds to produce even more suckers. This mechanism makes simple top-kill treatments ineffective and necessitates a systemic approach that travels deep into the root network.
The Biological Window: Optimal Timing for Translocation
The best time to achieve complete sumac eradication is during the late summer through early fall, typically from August through the end of October. This period is often referred to as the plant’s biological window because it aligns with a fundamental physiological shift. During the spring and early summer, the plant uses energy to produce new leaves and stems, moving nutrients upward from the roots to the growing tips.
As the days shorten and temperatures cool, the sumac prepares for winter dormancy by reversing this flow, beginning the process of translocation. The plant actively moves stored starches, sugars, and other nutrients from the leaves and stems down into the roots and rhizomes. Applying a systemic herbicide during this downward movement maximizes the amount of chemical transported to the underground root structures. This ensures the herbicide reaches and kills the entire interconnected rhizome network, rather than just the visible stems above ground.
This strategic timing differentiates a successful, long-term kill from a temporary top-kill that only causes the plant to resprout more vigorously the following year. When the herbicide is translocated with the plant’s nutrients, it can effectively eliminate the persistent root buds and drain the energy reserves that fuel the colony. Treating outside of this window is significantly less effective because the plant is not actively moving materials.
Targeted Eradication Strategies Based on Seasonal Timing
The optimal timing window demands specific methods to ensure the applied chemical is effectively delivered into the plant’s vascular system. The two most effective techniques used in late summer and fall are the cut-stump method and the basal bark treatment.
The cut-stump method involves cutting the sumac stem close to the ground, then immediately applying a concentrated, systemic herbicide to the fresh cut surface. This application must focus specifically on the cambium layer, which is the thin ring of actively growing tissue located just inside the bark. Since the plant begins to seal the wound quickly, the herbicide must be applied within minutes—ideally within five to ten minutes—of making the cut to ensure maximum absorption into the downward-moving sap stream. Herbicides containing triclopyr or glyphosate are commonly used for this method, often at higher concentrations than typical foliar sprays.
For smaller sumac stems, typically those less than six inches in diameter, the basal bark treatment offers an alternative that avoids cutting. This method involves applying an oil-soluble herbicide, such as triclopyr formulated with an oil penetrant, directly to the bark. The chemical solution is sprayed entirely around the lower 12 to 15 inches of the stem, ensuring it soaks down to the root collar. This technique is highly selective, minimizing damage to surrounding non-target vegetation, and can be performed any time the ground is not covered in snow or water.
Methods employed outside of the late-season window are often less successful. Foliar spraying, which involves coating the leaves with a chemical, is usually performed during the active growing season. This technique often results in a quick top-kill of the leaves and stems, but it rarely eradicates the entire root system. Because the plant is moving resources upward during this time, the chemical does not travel sufficiently down to the rhizomes, leading to aggressive resprouting from the root suckers.
Long-Term Monitoring and Follow-Up Treatments
Achieving complete eradication of a sumac colony is rarely accomplished with a single treatment due to the size and persistence of the underground rhizome network. The process requires a commitment to long-term monitoring and follow-up treatments, often extending over two or three subsequent growing seasons.
Even after a successful late-season application, the stored energy reserves in the roots will likely cause new suckers to sprout the following spring and summer. These new sprouts must be located and treated promptly to prevent the root system from regaining strength through photosynthesis. New suckers can be spot-treated using a low-concentration foliar spray of a systemic herbicide, or by repeated cutting and mowing to exhaust the root system’s energy reserves.
Regular inspection of the treated area is necessary, as suckers may appear at different times throughout the season. By consistently interrupting the plant’s ability to photosynthesize and replenish its root reserves, the entire colony will eventually be starved and eliminated.