Russian olive is a non-native species introduced to North America for ornamental and windbreak purposes, but it has since become an aggressive invader of riparian and rangeland ecosystems. Its prolific seed production and ability to rapidly re-sprout from its extensive root system make mechanical removal alone largely ineffective. For complete, long-term eradication, especially of mature trees, a chemical control strategy is the most reliable method for ensuring the root crown and entire root network are permanently killed.
Recommended Herbicidal Agents
The most effective chemical control for Russian olive involves systemic herbicides that reach the roots. Herbicides containing the active ingredient triclopyr are effective on woody plants, particularly when applied to the bark or stump. Triclopyr is often prepared as an ester formulation, which mixes readily with oil carriers, allowing it to penetrate the thick, waxy bark of woody species.
For basal bark treatments, a concentration of the triclopyr ester product typically ranges from 20% to 50%, mixed with a basal oil carrier. This high concentration ensures the chemical can move through the bark and into the cambium layer to reach the roots. Another highly effective agent is glyphosate, a non-selective herbicide that is commonly used for cut-stump applications.
When using glyphosate for cut-stump treatment, it is often applied in a high-concentration solution directly to the freshly cut surface. Some professionals also rely on imazapyr for stump treatments due to its high efficacy, though it carries a greater risk of non-target damage because of its residual activity in the soil. Regardless of the agent chosen, the specific method of delivery determines the required concentration and the necessary mixing agent, such as oil or water.
Targeted Application Techniques
Chemical eradication succeeds by applying the herbicide directly to the plant’s living tissues using precise methods. For trees with a diameter less than six inches, the basal bark application is a highly efficient technique that avoids cutting the tree. This method requires mixing the concentrated herbicide with a basal oil to penetrate the bark.
The mixture is sprayed around the entire trunk from the ground line up to a height of 12 to 18 inches. The application should thoroughly wet the bark but not to the point of excessive runoff. For larger, mature Russian olives, the cut-stump application is the preferred method.
Immediately after the tree is cut, the herbicide mixture must be applied to the freshly exposed stump surface. The treatment must be focused on the cambium layer, which is the thin, lighter-colored ring of tissue just inside the bark. Applying the chemical to the center heartwood is wasteful, as this area is no longer actively transporting nutrients and water to the roots. The entire application must be completed as quickly as possible, ideally within five to fifteen minutes of the final cut, before the tree’s natural defense mechanisms seal off the vascular tissues.
Seasonal Timing and Safety Protocols
The time of year significantly influences the effectiveness of systemic herbicide treatments on Russian olive. Applications made during the late summer, early fall, or during the tree’s dormant winter season often yield the best results. During these periods, the tree is actively translocating nutrients and resources down to the root system for storage.
The downward flow of these resources acts as a carrier, pulling the herbicide deep into the root mass for a complete kill. Conversely, application should be avoided during the early spring when the tree is experiencing a strong upward flow of sap, which can dilute the herbicide and prevent it from reaching the roots. Cut-stump treatments can be performed almost year-round, provided the temperatures are above freezing and the stump is dry.
Always wear the required personal protective equipment, including chemical-resistant gloves, long sleeves, and eye protection, as specified on the product label. To prevent contamination of non-target plants and water sources, avoid applying herbicides during windy conditions or when rain is expected shortly after application. Adding a commercial dye to the herbicide mixture is also a good practice, as it allows the applicator to easily see treated areas and avoid missed spots or over-application.