Sumac (Rhus) is a fast-growing shrub or small tree that often forms dense, aggressive colonies. While certain species are valued for their fall color, their tendency to spread vigorously through underground root systems, called rhizomes, makes them a significant management challenge. Complete removal requires a targeted approach that addresses both the above-ground growth and the extensive root network. Achieving long-term eradication demands persistence and a combination of mechanical and chemical strategies.
Identifying the Sumac Species
Before initiating any removal efforts, correctly identify the specific sumac species present, particularly to distinguish between common, non-toxic varieties and Poison Sumac (Toxicodendron vernix). The typical landscape sumacs, like Staghorn Sumac (Rhus typhina) and Smooth Sumac (Rhus glabra), aggressively form thickets but do not cause contact dermatitis. These common sumacs have compound leaves with between 11 and 31 serrated leaflets along the stem. Their fruit clusters are red, dense, and grow upright at the branch tips.
Poison Sumac, conversely, is highly toxic and contains urushiol, the irritant oil found in poison ivy and poison oak. This plant is usually found in wet, swampy areas and has compound leaves with fewer leaflets (typically 7 to 13) that have smooth edges. The key distinguishing feature is the fruit, which is small, waxy, and whitish-green, drooping downward from the branches. If identification is uncertain, always wear long sleeves, long pants, and gloves to protect the skin from potential allergic reactions.
Mechanical Removal Strategies
Mechanical removal is a non-chemical option for managing small, young sumac infestations or in areas where herbicide use is not desired. The primary focus must be the complete removal of the root crown and as much of the rhizome system as possible. For small seedlings or suckers, manual pulling can be effective, provided the entire root piece is extracted.
For established plants, simply cutting the main stem stimulates the root system to generate new suckers. The process requires digging around the base to expose the root crown, where the stem meets the root system. Tools like a shovel, mattock, or grub hoe are necessary to loosen the soil and excavate the thicker, lateral roots. Thorough root excavation is required, as every piece of root that remains in the soil has the potential to sprout a new shoot.
Chemical Control and Timing
For larger or established sumac colonies, a targeted chemical approach is often the most efficient way to achieve complete eradication by directly targeting the extensive root system. Systemic herbicides containing glyphosate or triclopyr are effective against woody plants like sumac. These chemicals are translocated down into the roots, which is the only way to kill the underground network of rhizomes responsible for spreading.
The most effective application method is the “cut-stump” treatment. This involves cutting the sumac stem close to the ground and immediately applying a concentrated, undiluted herbicide to the fresh cut surface. The application must be done quickly, within five to ten minutes of cutting, before the plant tissue seals off and prevents absorption. Applying the herbicide with a brush, sponge applicator, or squeeze bottle ensures the chemical is precisely targeted and avoids contact with surrounding vegetation.
The timing of the application is paramount to success because it maximizes the plant’s absorption and movement of the herbicide to the roots. The best time to treat sumac is in the late summer or early fall, typically August through September. During this period, the sumac is actively transporting nutrients and carbohydrates down to the roots in preparation for winter dormancy, pulling the systemic herbicide with these resources. Basal bark treatment, which involves spraying an oil-soluble triclopyr mixture around the lower 12 to 18 inches of the intact trunk, is an alternative for smaller stems.
Managing Suckers and Preventing Recurrence
The most challenging aspect of sumac removal is managing the inevitable emergence of new root suckers, which are stimulated when the main top growth is removed. Sumac’s extensive rhizome system stores significant energy reserves and will rapidly attempt to regenerate by sending up numerous shoots from dormant buds on the roots. This biological response means that initial removal is only the first step in a multi-year eradication process.
Long-term management requires continuous and consistent monitoring of the treated area, as suckers can appear within weeks or even the following growing season. Any new shoots must be promptly addressed before they can develop enough leaf area to begin replenishing the root system’s energy reserves. Small suckers can be pulled by hand, while a foliar spray of a diluted systemic herbicide can be applied to new, leafy growth.
Repeated cutting or mowing of new shoots without herbicide is a slow process that simply starves the root system over time by removing the source of photosynthesis. For complete eradication, it is often necessary to return to the site multiple times during the second and even third year to treat all new growth until the root system is finally exhausted.