Lawn treatment programs have a two-prong approach:  fertilization and weed control.  With Traditional service, both are chemical treatments.   With Organic, the fertilization is organic and the weed control is a chemical.  There is not anything naturally occurring that exclusively targets weeds.  You can pour vinegar on your lawn and it is going to kill both grass and weeds, without discriminating.  With the Organic method, you are using less chemicals on your lawn.