Got Nature? Blog

Question: I have 2,700 young white oak and hickory trees that were planted in 2017 that now have black locust creeping in. Should I try to remove them by cutting them down and treating the stumps? What is the best treatment to control the brush?

Cut stumps treated with herbicide including a dye to show application. Photo by Lenny Farlee.

Answer:  Whether eliminating black locust competing with oaks in a tree planting, or controlling invasive woody shrubs like autumn-olive or Asian bush honeysuckles, cutting the stems near ground-line and treating the stumps with an appropriate herbicide provides a one-two punch to the target plant. Severing the stems from the roots cuts off the flow of photosynthesis-produced food to the roots, and may prevent production and ripening of seed, if done early enough in the growing season. The stump left behind provides a small target area for herbicide application, limiting the damage to nearby native plants that can result from foliar herbicide overspray and drift. The herbicide application should kill the roots and limit re-sprouting. While it requires two sequential operations, cutting and spraying, it may be one of the most efficient methods to control many smaller-diameter woody plants due to the high rate of control achieved when done correctly and limited damage to surrounding desirable vegetation.

So how do you do the “cut-stump” treatment correctly? Several factors need to be considered, but some common elements to effective and efficient treatments include a cutting tool you can operate safely, effective herbicide type and application, and correct timing for the site and situation. Tools can be powered by fuel or electric motors or by your muscles. Be sure you know how to operate them safely and wear appropriate safety gear. I prefer brush saws for near-ground cutting as it limits bending over and is safer to operate than a chainsaw, but they will struggle with some larger diameter or denser stems a chainsaw could cut easily. Handsaws, loppers, pruners, or blade-tools like machetes and brush-hooks are hand-tool options, but larger stems will require more time and effort to cut or will be too large for some hand-tools to handle. Herbicides should be applied immediately after you have cut off the stems. A good choice for many applications is herbicide containing the active ingredient Glyphosate. Glyphosate concentrate herbicides containing 42% or more active ingredient are widely available at many garden and farm stores. Read the label before using the herbicide to confirm the active ingredients, concentration, and requirements for safe and effective applications, including the appropriate safety gear during dispensing and application. Apply the concentrate straight or mixed with up to 50% water to the cut surface immediately after the cut is made. For stems over 3 to 4 inches in diameter, you can apply a band of spray around the perimeter of the stump so the bark, cambium and some sapwood is treated. If you wait to apply the spray to cut surfaces a dozen minutes to hours after the cut is made, two things will happen that can impact the effectiveness of the spray. The surface of the stump will seal as it dries, preventing the entry of the water/herbicide mixture into the plant. You may also have difficulty tracking down the cut stumps if the area is weedy and brushy.

Hand-cutting tools suited for small diameter woody plants. Photo by Lenny Farlee.

Some cautions about timing and locations of this application method. Many plants are pumping lots of sap up from the roots in spring. That sap can flush herbicides out of the application area and result in herbicide failure and re-sprouting from the root system. If the stem is frozen, usually 25 degrees F or colder, herbicide may also not penetrate and evaporate off the frozen stump. Also avoid applications when rain could wash off the herbicide within two or three hours of application.

Several other herbicides are available for this treatment including Triclopyr and 2-4-D/Picloram herbicides. Be sure to read the labels and understand the safety requirements and application instructions before using.

For additional information see the Purdue Extension-FNR webinar Invasive Plants Threaten our Forests Part 2: Control and Management.

More resources:
District Forester, Indiana DNR Division of Forestry, for over 10 acres of woodlands
Directory of Professional Foresters, Indiana Forestry & Woodland Owners Association (IFWOA)
Indiana Woodland Steward E-newsletters, Eleven Member Organization
A Woodland Management Moment, Playlist, Purdue Extension – Forestry and Natural Resources (FNR) Youtube Channel
Conservation Tree Planting: Steps to Success, Purdue Extension – FNR Youtube Channel
Forest Improvement Handbook, The Education Store
Invasive Species, Playlist, Purdue Extension – FNR Youtube Channel
Woodland Stewardship for Landowners, Playlist, Purdue Extension – FNR Youtube Channel
Invasive Plant Species Identification, Video, Purdue Extension – FNR Youtube Channel
Report Invasive Species, Purdue Invasive Species
The GLEDN Phone App – Great Lakes Early Detection Network
EDDMaps – Early Detection and Distribution Mapping System
Indiana Department of Natural Resources: Invasive Species
Indiana Invasive Species Council
Cooperative Invasive Species Management Area (CISMA)
Invasive plants: impact on environment and people, The Education Store, Purdue Extension’s resource center
A Landowner’s Guide to Sustainable Forestry: Part 7: Managing for a Diversity of Value-Added Forest Products, The Education Store
Investing in Indiana Woodlands, The Education Store
Woodland Invaders, Got Nature? Blog, Purdue Extension – FNR
The Education Store, Purdue Extension’s resource center (place keywords in search bar, for ex: invasive, forest, timber)

Lenny Farlee, Extension Forester
Purdue University Department of Forestry and Natural Resources