Cressleaf Groundsel Identification and When to Control

Cressleaf groundsel (Packera glabella formerly Senecio glabellus) is a winter annual that is a member of the Aster/Composite family (Figure 1). It goes by many other names, including butterweed, yellow top, golden ragwort, and yellow ragwort. Other members of the Aster family include wild sunflower, purple coneflower, and cocklebur.

It most often becomes an issue in no-till/strip till fields as well as pastures where tillage isn’t used as a control measure. The weed prefers moist or wet growing conditions and has been known to become an issue in wetter years.

Identification

As a winter annual, cressleaf groundsel emerges in the fall and forms a rosette of leaves (Figure 2). The leaves are quite variable and deeply lobed in the rosette stage. In spring, it bolts, develops flowers, and produces seed. The bolting stems are hollow and can reach up to three feet in height (Figure 1). The flowers contain between six to twelve yellow ray flowers that are often compared to the flowers of common dandelion (Figure 3). Mature plants produce hundreds of thousands of small seeds that can be readily moved by the wind.

The leaves, flowers, and seeds of cressleaf groundsel contain alkaloids that cause liver damage or seneciosis in livestock. Symptoms of seneciosis are loss of appetite, sluggish behavior, and in extreme cases, walking without regard to fences or structures. Livestock producers encountering cressleaf groundsel in pasture ground should take steps to avoid prolonged ingestion by their animals.

Management and Control

Like most other successful weed control programs, cressleaf groundsel is best controlled by combining multiple methods of weed control including cultural, mechanical, and chemical. As a winter annual, fall or spring tillage in row crops would be a very effective way of controlling or reducing populations of cressleaf groundsel. Herbicide applications are most effective when applied in the fall on plants in the rosette stage (Figure 2). When plants are larger or in the bolt stage, they become extremely difficult to control. In row crops, a fall application of a pint of 2,4-D herbicide applied to actively growing rosettes is a common control.

Spring herbicide burndowns have proven to be difficult for cressleaf groundsel control, especially if the plants have an increased size or the weather is cooler. Adding atrazine in a burndown prior to planting corn or chlorimuron prior to planting soybean can aid in burndown control. Labeled in-crop applications to herbicide tolerant crops of a Roundup^® brand of agricultural herbicide, Liberty^® herbicide, or dicamba herbicide can be very helpful for managing cressleaf groundsel. In pastures, cressleaf groundsel can be controlled in the fall or early spring with a labeled application of 2,4-D or dicamba while in the rosette stage.

Channel Agronomist
Andrew Sikora

Sources:

Zimmer, M. and Johnson, B.2021. Cressleaf groundsel (Packera glabella). Pest&Crop newsletter. Extension Entomology. Purdue University. https://extension.entm.purdue.edu/newsletters/pestandcrop/article/cressleaf-groundsel-packera-glabella-4/.

Bradley, K. 2010. Weed of the month. Cressleaf groundsel or butterweed. Integrated Pest Management. University of Missouri. https://ipm.missouri.edu/cropPest/2010/4/Weed-of-the-Month-Cressleaf-Groundsel-or-Butterweed/.

Websites verified 11/14/22. 1123_436451