Weed Identification Series, Barnyardgrass

Mark Renz UW Madison Associate Professor and Extension Specialist, Chelsea Zegler UW Madison Associate Research Specialist

Well the season is nearly over, but we wanted to point out a weed species that had a prolific year: Barnyardgrass. This species has long been present in Wisconsin, but until this year I rarely saw it in fields. This year it was common throughout the state in fields, on the side of roads, in ditches, wetlands, and even in urban areas. I chalk this up to the wet year, as this species prefers wet vs dry soils. Once established however it will survive in a range of conditions, so it should be no surprise that it ranks as one of the world’s worst weeds. It has been documented to be a serious weed in over 42 countries.

Barnyardgrass is a summer annual grass that begins to germinate in May with the foxtails. If present it can grow as large if not larger than foxtails, but one of the reasons I bring up this species at the end of the year is it can produce huge numbers of seeds. Research has shown that one plant can produce in excess of 750,000 seeds. Doing some quick math and looking at some of the populations I think it is safe to assume we will have large barnyardgrass seedbanks in our soil for years to come. The bad news is that seeds can remain viable for up to 4 years, even longer under specific conditions.

The good news is this plant is a fairly easy annual grass to identify. It lacks a ligule and auricle (see factsheet if you don’t know what those are) and has flattened stems. These three characteristics make it easy to identify when young before it flowers. We have a range of products in crops we grow that effectively manage this plant.

So in conclusion be on the lookout for this plant in 2018, especially if seen nearby in 2017. Check out the factsheet to learn about how to ID this species.

For more information on this species from the Weed Science Society of America click here