Common names: Carpetweed, Indian chickweed, whorled chickweed, devils-grip, green carpetweed
Latin name: Mollugo verticillata L.
Family: Molluginaceae
General Description and Life Cycle
Carpetweed is a summer annual. Compared to other summer annual weeds, its germination is usually later in the summer. The plant grows rapidly and reproduces by seeds. Carpetweed is mostly found in dry and sandy soils but can be found on disturbed land throughout Indiana.
Identification
Seedlings develop as small basal rosettes (Figure 2). It has oblong cotyledons (seed leaves) that are smooth and 1.5 to 3.5 mm long. Young leaves are alternate, with a rounded shape at the tip and narrow at the base. Leaf surfaces are pale green, smooth, and pink or brown close to the base.
Figure 1. A carpetweed seedling (Photo by J. Cerritos).
Mature Plants
Carpet weed has smooth stems with abundant branching, forming a dense low mat above the soil surface (Figure 2). Whorled leaves radiate out from the center of the plant with each whorl containing 3 to 8 leaves; each leaf is 1 to 3 cm long and less than 1 cm wide.
Figure 2. A mature carpetweed plant growing in a watermelon field (Photo by J. Cerritos).
Flowers
Carpetweed flowers may sporadically emerge as early as June, but their bloom period typically spans July through September. Small clusters of 2 to 5 white to greenish-white flowers form within the leaf axils, each measuring approximately 4 to 5 mm in diameter. The flowers are connected to the plant by pedicels ranging from 1.5 to 4 mm in length (Figure 3).
Figure 3. Carpetweed with small white flowers (Photo by J. Cerritos).
Carpetweed and catchweed bedstraw
Carpetweed is sometimes mistaken for catchweed bedstraw (Gallium aparine) due to its similar whorled leaves. Catchweed bedstraw is easily recognized by its square stems and slightly hairy leaves. Unlike carpetweed, which grows close to the ground with a prostrate habit, catchweed bedstraw tends to grow more upright.
Management
Carpetweed is recognized as a weed that is easier to manage than other summer annual broadleaf weeds. Its growth habit and shallow roots (Figure 4) make it simple to pull out of the soil by hand or with cultivation. If using herbicides is necessary, effective herbicides for managing carpetweed include S-metolachlor, flumioxazin, and DCPA for pre-emergence control, as well as flumioxazin, glyphosate, and 2,4-D for post-emergence weed control. Using herbicides containing the active ingredient clomazone seems to increase carpetweed emergence. Always read the label and follow approved rates and guidelines for application. Visit mwveguide.org for more information about herbicides registered in the vegetable crops you grow.
Figure 4. Carpetweed has shallow roots (Photo by J. Cerritos).
Interesting facts
Carpetweeds are often overlooked as harmless weeds but can serve as hosts for root-knot nematodes. Interestingly, carpetweed foliage can be cooked and eaten.
References
Neal, J.C., Uva, R.H., DiTommaso, J. M., DiTommaso, A. 2023. Weeds of the Northeast. Second edition by Cornell University.
Singh, S. K., Khurma, U. R., & Lockhart, P. J. (2010). Weed hosts of root-knot nematodes and their distribution in Fiji. Weed Technology, 24(4), 607–612. https://doi.org/10.1614/wt-d-09-00071.1