– Jordan Penrose, Ohio State University Extension Agriculture and Natural Resources Educator, Gallia County
Small carpetgrass is a new annual invasive grass weed.
Earlier this fall as dad and I were going along checking and fixing fence along a field that we have been stockpiling for cattle, we found a grass that we had never noticed in the field or on the farm before. The first thought that came to mind was that it was Japanese stiltgrass, but after looking up some pictures of Japanese stiltgrass on our phones, we determined it was not. Then we went and used a plant ID app on a phone to see what it would come with, and it identified it as small carpetgrass. To verify, we searched for small carpetgrass on the internet looking at an Extension website to confirm.
Small carpetgrass also known as joint-head grass, was introduced into the U.S. from Japan and eastern Asia. The earliest reports of the plant are from the early 1970s. Small carpetgrass is an annual invasive grass weed that thrives in sunny, moist areas and prefers wet habitats like stream banks, pond and lake margins, wetlands, and disturbed areas. We found it an area where the soil gets disturbed from where we feed round bales on pasture in the winter. This fall we did notice the grass died off with the first frost and that our cattle avoided eating it. What stuck out the most about this grass was the patches of this burgundy color in the field, which turned out to be the seed head, this was on the first of October that we noticed the grass. This grass really showed up in the middle of August when we started to stockpile this field after mowing it. Some of the other identifying features include a smooth hairless stem and oval to lance-shaped leaves that are one to three inches in length with heart-shaped bases. The leaf margins have conspicuous hairs and flowers are contained in one to several three-inch-long spikes and bloom in early fall. This grass can grow up to one and a half to two feet tall, with carpet-thick stands in pastures and hayfields, which can choke out desirable plants.
Small carpetgrass like moist areas.
Small carpetgrass can easily be mistaken with a few other grasses like Japanese stiltgrass. Which is like small carpetgrass in some ways, liking moist areas, growing up to two feet tall, being an invasive annual grass that can form a mat over an area, and will take over in areas that are disturbed. The differences are that Japanese stiltgrass comes in mid to late spring and small carpetgrass comes in mid-summer. Also, the leaves of Japanese stiltgrass are lance-shaped and asymmetrical with a reflective midrib and likes shady, forested areas. Small carpetgrass also looks similar to deertongue grass. Deertongue grass is slightly larger, covered with stiff hairs and the leaves are typically longer and more lanceolate in shape.
If Small carpetgrass invades large areas, chemical control may be required.
Small carpetgrass should be controlled before any seed forms. If you have small areas of it, manual techniques like hand-pulling and mowing may be the best option for control. However, if you have large areas or an entire field taken over by small carpetgrass, chemical control may be the best option. Unfortunately, since this is a grass, any herbicide used to control small carpetgrass will likely also kill desirable grasses. Glyphosate-based products are the most effective, but they are non-selective. Care should be taken when selecting herbicide products due to the propensity of the plant to grow in and around wetlands, where pesticide use is restricted to certain aquatic-safe formulations. When using pesticides, make sure to read and understand the label before you use the product.