Howard F. Schwartz, Colorado State University, Bugwood.org
Dandelions are some of the most common weeds in the country, growing as bright yellow flowers throughout lawns across the U.S. They're also known because of the white puffball seed heads, which are easily dispersed in the wind, causing more of an infestation. These weeds thrive in most any soil condition and emit a milky sap if the stems are broken.
Keeping the turf thick and healthy is one way to combat a dandelion infestation. Proper mowing and fertilization is the key to keeping them out of the lawn. When the temperatures are still cool, apply a postemergent herbicide to kill any weeds that overwintered. Pre-emergent applications are also helpful to prevent any seed heads from appearing.