Asiatic Dayflower Pretty but Hard to Control

Glenn Nice, Weed Diagnostician, Department of Botany & Plant Pathology, Purdue University

Asiatic dayflower (Commelina communis) can be a problematic weed in lawns and gardens, but it appears over the past several years to be spreading into no-till corn and soybean. It is one of the 16 weeds mentioned in the “Weed to Watch” handout (if you would like a copy of this handout please contact me – gnice@purdue.edu). Bill, Tom, and I get the odd call regarding Asiatic dayflower. As the common name would suggest, Asiatic dayflower was introduced to the US from Asia.

Asiatic dayflower is a member of the Commelinaceae or spiderwort family. This annual plant is a monocot with alternative lanceolate leaves that are 2 to 4 inches long (Figure 1). The base of each leaf clasps the stem. Rarely Asiatic dayflower has been misidentified as a grass with fleshy wide leaves. Although this might happen before it flowers, once it flowers, it can’t be mistaken for a grass any longer. Asiatic dayflower has distinctive blue flowers approximately 0.5-1 inch wide with three petals. Flowers appear from June to October¹. The flowers consist of three petals and three sepals, two larger petals above and one smaller below. The above two petals are blue and the one petal below appears faded blue or white².

There are few herbicides that are effective on Asiatic dayflower. This is one of the problematic weeds that glyphosate does not have much efficacy on suppression only. Calls regarding this plant often are a result of poor control with glyphosate. Iowa State University research reported that three applications of glyphosate (0.75 lb ae/A); at planting, 44 days after planting, and 63 days after planting provided over 80% control. Cloransulam-methyl (FirstRate®) plus sulfentrazone (Spartan®) also provided over 80% control³. The combination of these two products can also be found in Authority First®. In this study, clomazone (Command®), bentazon (Basagran®), acifluorfen (Blazer®), lactofen (Cobra®), fomesafen (Flexstar®), and imazamox (Raptor®) did not have much activity.

Sources:

1. Connecticut Botanical Society. Asiatic dayflower Commelina communis. Accessed June 29, 2007 [http://www.ct-botanical-society.org/galleries/commelinacomm.html]

2. L. Newcomb. 1977. Newcomb’s Wildflower Guide. Little, Brown and Company New York – Boston. p 40.

3. B. Hartzler. 2003. Dayflower: A weed to watch? Accessed June 29, 2007 [http://www.weeds.iastate.edu/mgmt/2003/dayflower.shtml]

Click image to enlarge

Figure 1

Figure 2