Purple deadnettle is not a common weed for Wisconsin, but it might be one weed to be familiar with. These pictures were sent from Iowa County, where it was not controlled well with glyphosate in the past. Purple deadnettle also shows up in herbarium records from Dane, Sheboygan, and Walworth counties. Typically, I associate this winter annual weed with states to our south such as Illinois, Indiana, Ohio, and Tennessee. If you have driven through these states in the spring and noticed “purple” fields, you were probably looking at purple deadnettle.  

 

Identification:   Purple deadnettle (Lamium purpureum L.) is a winter annual and has the characteristic square stem and opposite leaves of the mint family. The plants are branched at the base with stems that can grow over 12 inches tall. As seen in the left photo, lower leaves have a longer petiole (leave stalk) while upper leaves still have a short petiole. The leaves are triangular to heart shaped with a toothed margin as shown in the right photo. Upper leaves are often tinged with purple and the plants also have purplish flowers. 

 

Purple deadnettle looks quite similar to henbit, another winter annual weed. Henbit is also in the mint family with a square stem and opposite leaves and has a similar type of growth. However, the key differences that you can use to separate these two weeds are that the upper leaves of henbit lack a petiole. The henbit leaves appear to clasp the stem while deadnettle leaves have a short petiole. Purple deadnettle leaves also have the red or purple coloring and more triangular shaped leaves while henbit leaves are generally green and round. 

 

Management:  Both purple deadnettle and henbit are winter annuals with relatively shallow root systems. As such, we shouldn’t expect them to be problems in tilled fields. However, they can be a problem in winter wheat fields and in particular no-till fields. In no-till fields, glyphosate or 2,4-D alone are not reported to be consistent in controlling purple deadnettle. There is some discrepancy about the consistency of the combination of glyphosate plus 2,4-D, but this should increase control over either herbicide alone. Treatments that include atrazine or atrazine premixtures are generally rated high in corn. In soybeans, AuthorityFirst/Sonic/Valor plus glyphosate plus 2,4-D are treatments that generally get good but not excellent control ratings.