My spreading evergreens used as a ground cover have grass and weeds. It is impossible to pull most of them. How can I get rid of the grass and weeds? Have you ever used Treflan over the top spray? If so where can it be purchased?
The Gardener’s Answer
Eliminating weeds in the garden is a job that never ends, but getting them under control is the first step. Weeds not only look unsightly but compete for nutrients, moisture, and sunlight that intentional plantings need to thrive. Removing them when they are literally growing up through landscape plants is tricky, but doing so before they flower and produce seed is an important step in controlling them.
The safest option is to hand pull the weeds; it may require a lot of elbow grease, but working in small sections will make it feel less overwhelming. You will have to get in there and under the evergreens to remove the roots so a long sleeve shirt and gloves will be your friends.
The other option is having the weeds properly identified and using a selective herbicide that is labeled for the weeds you are dealing with. You are welcome to send pictures for identification, or the horticulture/agriculture agent(s) at your county Cooperative Extension are a reliable source as well as nurseries/garden centers with a knowledgeable staff.
Treflan is the trade name for a selective herbicide for the pre-emergence control of many annual grasses and broadleaf weeds. It is applied before planting to prevent germination and used in commercial agriculture fields, although it is readily available to homeowners. Trifluralin is the active ingredient, and Preen is maybe the most common product found on garden center shelves. It will not do anything to help the existing weeds.
Spraying with a non-selective herbicide such as Round Up (glyphosate) will injure your evergreens. You can use a paintbrush or purchase the gel option to avoid the herbicide coming into contact with your ground cover. As with any chemical product, always read instructions and apply according to directions. Be prepared to make more than one application.
Once the weeds are under control, the next step is to prevent them from coming back. This is when pre-emergents are helpful. Corn gluten meal is an organic option. These products don’t differentiate between weed seeds and seeds that were intentionally planted, but if you don’t plan on growing anything from seed in this space, it is a great option. A 2-3 inch layer of mulch will also help keep the weeds down.