PPDL Picture of the Week for

May 18, 2015

Fields of Yellow

Travis Legleiter, Weed Science Professional Assistant, Botany & Plant Pathology Department

As the spring has progressed into early May you may have notice some fields that have turned from green weeds to bright yellow.   It is most likely you have saw this in no-till fields especially in southern Indiana.  The weed that is responsible for turning the landscape yellow is cressleaf groundsel, which is also known as ragwort and butterweed. 

This yellow flowering weed is often confused with the mustard family because of its deeply lobed leaves and yellow flowers.  Upon closer inspection it is much different than the mustards though and have several distinguishing characteristics.  Cressleaf groundsel is a winter annual that emerges in the fall as a rosette and has the distinct deeply lobed leaves, in the spring the plant bolts on a hollow stem, and produces the bright yellow ray flowers.  The characteristics that set cressleaf groundsel apart from the mustards include the hollow stem and the ray flowers.  The mustards will have a solid stem, will have four petal yellow flowers, and have the distinctive silique seedpods that cressleaf groundsel lacks.

While cressleaf groundsel typically does not compete directly with crops, as it is usually gone by late spring due to its winter annual growth cycle, it can delay crop planting.  As with many winter annuals the dense populations of plants in field keep the soil from drying and warming up causing a delay in planting.  The most effective method of control is to apply a burndown in the fall when plants are small.  A burndown can also be applied in the spring, although at this point the weeds have already produced seed that will contribute to future generations.

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​Click image to enlarge

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Fig. 1-A field of cressleaf groundsel in southeastern Indiana.
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Fig.2-The deeply lobed rosette leaves of cressleaf groundsel.
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Fig. 3. Yellow ray flowers produced by cressleaf groundsel​