Mid-June 2020

CCE Field Crops Specialist Mike Stanyard ran across this weed in winter triticale. It appeared to have been seeded with the triticale, as it was only growing in the row, as tall as the heading out triticale. Scott Morris of the Cornell Weed Ecology and Management lab identified it as common corncockle (Agrostemma githago), a common weed seed contaminant in grain crops. Identifying traits include narrow, opposite leaves with long hairs, and single, purple five-petaled flowers which bloom at the top of a long stalk over the summer. Common corncockle is mildly toxic to humans and livestock when ingested.

This was historically a significant weed of European grain crops, but largely disappeared from its native range due to the advent of herbicides, improvements to seed cleaning technology, and the shift to winter wheat. Herbicide resistance to 2,4-D and MCPA is mentioned in an article from the 1980s on corn cockle competition from eastern Oregon, but the species is not listed in the International Database of Herbicide Resistant Weeds maintained by the Weed Science Society of America. It is listed as a noxious weed in Arkansas and as a plant pest in South Carolina. Common corncockle is also used as a garden plant. 

References:

Bugwood.org’s listing for corn cockle: https://www.invasive.org/browse/subinfo.cfm?sub=5049

Wikipedia entry for corn cockle (also corn-cockle, corncockle): https://en.wikipedia.org/wiki/Agrostemma_githago

WSSA International Herbicide-Resistant Weed Database: http://www.weedscience.org/Pages/Species.aspx

Rycrych, DJ 1981. Corn Cockle (Agrostemma githago) competition in winter wheat (Triticum aestivum). Weed Science 29(3) pp. 360-363.

North Carolina Extension Gardener Plant Toolbox: Agrostemma githago: https://plants.ces.ncsu.edu/plants/agrostemma-githago/

USDA PLANTS Database file for common corncockle: https://plants.usda.gov/core/profile?symbol=AGGI

Having a hard time telling these small plants apart? Us too! But this is often the stage when ID is most helpful. In the spring, a lot of plants are in rosette form, a clump of vegetation with no stalk. How to tell what’s in your field now, when you are planning weed management?

We’ve added a page just for this problem: Rosette Forming Weeds of Early Spring. We hope it will help you sort out your spring weeds. For assistance with management of the various species, please see Cornell’s crop and pest management guides and the references listed in the page.

PS – the photos above, starting from the left, are: horseweed, shepherd’s purse, Canada goldenrod, Virginia pepperweed, and common mullein. All photos by the Ohio State Weed Lab of Ohio Sate University except for shepherd’s purse (Steve Dewey of the Utah State University), Canada goldenrod (Michigan State University), and Virginia pepperweed (Joseph DiTomaso of the University of California at Davis). All photos available on bugwood.org.