Proper spring care will help grass recover quickly and reduce weed problems. Sharpen your lawn mower blades and check the cutting height before the mowing season begins. A sharp blade makes a clean cut that looks better and recovers faster. Set the mowing height at 3 to 4 inches. Mow often enough so you remove no more than a third of the total height, about an inch, of the grass at each cutting.
Taller grass is more drought resistant and better able to compete with weeds.
The pre-emergent will kill the lawn grass seeds as well as weed seeds. Reduce crabgrass problems by keeping the grass tall all season and watered during dry periods. If you decide to use pre-emergent weed killers, apply them in mid or late April when the soil temperatures reach 55 degrees and the forsythia bloom. Treat only problem areas and the surrounding few feet. This will allow you to control the problem and minimize your use of herbicides.