Here are the most common weeds and recommendations to eliminate. Annual bluegrass (Poa annua) Frequently found in compacted, infertile soils, this light green, low-growing grassy annual prefers cool-season growth, but can be found all year.  A sudden brown-out of the lawn in the heat of summer, or prolific seed production in spring, signals its presence.  When seeds appear, rake the grass upright, then mow, and bag the clippings. Crabgrass (Digitaria…