Cotoneaster, which has the botanical name of Cotoneaster pannosa is an evergreen shrub but behaves more like a ground cover because it spreads outward in a zigzag pattern. At maturity, it reaches up to 10 feet tall, but grows slowly and is often much shorter than this. Since contoneaster has an extensive root system, it often regrows after cutting it down. You must kill the remaining stump and root system with a systematic herbicide.
Cut off the top of the cotoneaster stumps by at least 1/2 to 1 inch to expose the inner white wood. Use loppers for most shrubs, but if the cotoneaster is large and has many stumps, a hedge trimmer will speed process.
Fill a bucket with 1 cup of an herbicide containing the active ingredient triclopyr and 3 cups of any cooking oil. Stir the mixture up with a paint stirrer to combine the two well. The cooking oil acts as a surfactant and causes the herbicide to adhere to the cotoneaster stumps better.
Insert a foam paintbrush into the herbicide mixture and paint it onto the cut sections of the cotoneaster stumps until they are saturated and completely covered.
Apply the herbicide as soon as possible after cutting the cotoneaster stumps because delaying the application will reduce the effectiveness. If desired, you can use an herbicide containing glyphosate instead of triclopyr, but it is not always as effective. If the cotoneaster shrub produced berries before you cut it down, the seeds will likely sprout in the spring. Remove them by pulling them up with your hands before they establish large roots.
Do not apply the herbicide when rain is in the forecast because it will wash it away and reduce the effectiveness.