After a long, cold winter, the grass has faced many damaging conditions. The lawn has been dormant for a few months. Without growth, the grass blades are fragile and tend to lie flat after being covered in leaves. The best way to help your lawn recover is to rake or de-thatch the soil which will clear away any debris and help stand the grass up properly. After doing this, it is best to apply a pre-emergent herbicide in order to help prevent weeds. Do this after the last frost or cold spell. Grassy weeds begin to germinate when temperatures are consistently above 50 degrees Fahrenheit and spraying for weeds only works best when the plant is actively growing.