Killing Tall Fescue
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At this time, there are no herbicides available for selectively killing tall fescue in turf lawns. That means that you can learn to live with the tall fescue, or kill all the grass and start over with good seed free of contaminants.
You can read about tall fescue in a publication on lawn weeds, “Lawn Care Pro Series: Perennial grassy weed control” from the University of Nebraska. You will find the publication at http://turf.unl.edu/pdfcaextpub/Properennialgrassyweedcontrol2012b.pdf Tall fescue is listed under bunch-type grasses on page 1.