Winter annual weeds (like chickweed, henbit, and annual bluegrass) germinate in cool, moist soils. While these small seedlings don't look aggressive, they can take over your fall-planted pansy beds.  Protect the beds from weeds by using mulches or preemergence herbicide(s). It is also important to control these weeds before they flower and shed seeds. Remember, most of the seedlings you see this year are from plants that were not controlled last year.  For information about keeping color beds weed free:  check out Weed Management in Annual Color Beds