White clover is a perennial broadleaf weed. It is commonly found in the northern half of the United States.
At one time clover was regularly included as an integral ingredient in lawn seed mixes. After the development of broadleaf weed controls that practice stopped. It is a low-growing plant with three-part leaves and white distinctive blossoms.
To some it may be considered attractive and it does help affix nitrogen to the soil. However, during periods of drought and in early fall the plant enters dormancy leaving unsightly brown patches in the lawn.
It emerges from dormancy in early spring and spreads by aggressive above and below ground stems. It also produces seeds that extends its range of growth.
In the fall, apply a postemergence herbicide that contains either triclopyr or mecoprop +2,4-D + dicamba. Spray while plants are actively growing on warm, but not hot, windless days.