January through March is the best time to apply Pre-Emergent and Post-Emergent Weed Control to prevent weed growth during the Spring and Summer months. A liquid post-emergent is needed for the control of existing winter grassy weeds and broadleaf weeds such as henbit and dandelions. Plus, a liquid pre–emergent is needed to prevent and control annual summer weeds like crabgrass, foxtail, clover and spurge. Lawn America is now applying this important weed control treatment.