If pulling weeds by hand from your yard seems like the only organic method for a weed-free lawn, think again: Just mow differently. Set the blades on your lawnmower to a higher setting and mow more often. Leave the grass clippings on the lawn to return the nutrients back into the soil. The higher grass and grass clippings will make it harder for weeds to thrive, since the grass blades will be stronger and denser. Now that it's the end of summer, add organic corn gluten meal to the lawn since it's a natural weed killer that won't hurt your grass. Adding this natural additive to your lawn will help reduce weeds by as much as 80 percent over the course of several years.