The Ohio State University

Home SportsNotes Following on from a SportsNotes posting at the end of September 2007 called Knotweed Going Dormant, the environment right now is obviously favorable for this weed to germinate and re-establish on those athletic fields that had bare soil in the high wear areas.

Germinating prostrate knotweed (Polygonum aviculare) is sometimes confused with crabgrass, but knotweed typically emerges about 1-2 weeks before crabgrass. This picture was taken 4/17/08 in central Ohio.

It is important to address the issue of why prostrate knotweed is on the field in the first place. It tolerates extremely compacted soils at the expense of desirable grasses, so compaction relief is critical. Good cultural practices that favor healthy turfgrass growth should prevent knotweed from coming in.

There are selective herbicides to chemically remove knotweed from grass but they will also prevent the desirable grass from germinating if seed is used to fill in the bare areas. It can be physically removed by hoeing or raking, leaving a seedbed area for new seed to establish. Once the new seed is several weeks old, a herbicide like Drive (quinclorac) can be used without negatively affecting the new grass.

Posted by Pam Sherratt & John Street