Answer: Even a lawn from the finest sod can be overtaken by native grasses and weeds. This is especially true if the lawn is not regularly maintained to keep it lush and thick enough to crowd out any newly emerging weeds. The best course of action now is to dig out the weeds, roots and all, and reseed the bare areas. Then mow often enough to keep the grass about 2" in length. Make sure the lawnmower blade is sharp. A dull blade not only rips the grass instead of cutting it, it can actually pull little grass plants out of the soil.
Weed 'N Feed does work to some extent. It's a fertilizer, herbicide combination. Fertilizer is good for the grass, and the herbicide will kill some, but probably not all of the weeds. If you use it, read and follow the label directions. I prefer to dig the weeds out, reseed, then put the lawn on a regular maintenance schedule, which includes regular watering (one-inch per week, applied thoroughly to encourage the roots to penetrate deeply into the soil), regular fertilizing (in April, June, September and December, using a 3-1-2 ratio of complete fertilizer), and mowing often enough to keep the blades only 1 1/2" - 2" high. When your lawn receives constant care it will reward you by crowding out weeds and providing a lush carpet of green.
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