Weed of the Week: Broadleaf Signalgrass

Written by: Blake Edwards, Jason Bond and Tom Eubank

Broadleaf Signalgrass

Family: Poaceae

Scientific name: Urochloa platyphylla (Nash) R.D. Webster

Synonyms: Signalgrass

Broadleaf signalgrass

Broadleaf signalgrass is a summer annual grass with wide, hairless leaves which tend to remain erect, and a fringed membranous ligule.  Hairs will be present on the margins of the leaf sheath and it can be easily confused with browntop millet (Urochloa ramosa) and large crabgrass (Digitaria sanguinalis).  Broadleaf signalgrass is distinguished from browntop millet by its ability to root at the nodes and a distinctive constriction near the end of the leaf blade.  This leaf constriction resembles an area of a leaf that was folded over to form a crease.  Whereas broadleaf signalgrass has a fringed membranous ligule and hairless leaves, large crabgrass exhibits a large, flat, membranous ligule and dense hairs on the upper surface of leaf blades.

Restriction near leaf tip on broadleaf signalgrass

Broadleaf signalgrass is widely dispersed throughout the southeastern region of the United States.  This weed can be found in crop production areas, pastures, roadsides, and lawns. In Mississippi, broadleaf signalgrass can pose a problem in most crops, but there are several effective pre- and postemergence herbicide options, depending on the crop. However, late in the season when control from residual herbicides has dissipated, broadleaf signalgrass can emerge and cause problems with harvesting.

Bryson, C.T. and M.S. DeFelice. 2009. Weeds of the South. Athens, GA: University of Georgia Press. pp. 421.

Broadleaf signalgrass rooting at the nodes.