Fall is a good time to renovate the lawn by spreading topsoil on top of the weeds at least one inch deep and then reseeding on top of the topsoil. This will smother many of the weeds and the new lawn will choke out the rest - or at least that is the idea. You may need to add lime to your lawn if you live in the PNW and aerate as many weeds grow due to poor drainage and acid soil. Improve the soil with a fertilizer and the weeds will not cope as well because the grass will outgrow the weeds - so you will not be fertilizing the weeds. Keep growing, Marianne Binetti