Pennywort

A common cool season weed is Large Leaf Pennywort

A common cool season weed is Large Leaf Pennywort; also called dollarweed (Hydrocotyle umbellata). This is a perennial weed that re-emerges in fall. The plant sports flat round leaves that measure 2″ to 4″ in diameter, grows in mounds about 6″ tall and produces tiny white flowers. It can be an especially frustrating weed in St. Augustine lawns, but will also be found in Bermuda grass lawns.