Cornell researchers identify natural herbicide that controls weeds around some common lawn grasses.Chronicle on line. Oct.22, 2007.Certain varieties of common fescue lawn grass come equipped with their own natural broad-spectrum herbicide that inhibits the growth of weeds and other plants around them.Cornell researchers have identified the herbicide as an amino acid called meta-tyrosine, or m-tyrosine, that these lawn grasses exude from their roots in large amounts. This amino acid is a close relative of para-tyrosine (p-tyrosine), one of the 20 common amino acids that form proteins [ See ]. The image (Frank Schroeder) shows fescue grass roots, which exude a yellow material that contains an amino acid called m-tyrosine as a major component. The chemical structure for m-tyrosine is superimposed on the photo.