Weeds that invade your fescue lawn not only present an aesthetic problem, but they also place your fescue in a stressful fight for water, soil space and nutrients. There are dozens of herbicide and weed-killing products on the market, but whatever you choose, follow the label dosing and application directions carefully. More herbicide is never better and too little will be ineffective. Spry the weeds when they are tender and young, in the spring or fall when ambient temperatures hover between 70 and 85 degrees F, as these elements help the weeds to metabolize the poison more readily.
Dicamba is an herbicide that controls a wide variety of broadleaf weeds in fescue. It is more effective on weeds that have a creeping growth form, such as purslane, spurge, knotweed and carpetweed.
A longtime controller for turf weeds, 2,4-D, is a broad spectrum herbicide. It is safe for use in fescue and is particularly effective on weeds that have a central taproot like plantain, dandelion, shepherd's purse and the mustard family of weeds. It is known to be less efficacious on white clover, ivy, chickweed and purslane.
MCPP is an active herbicide ingredient designed to kill weeds in fescue that have a vining growth habit, or cool-weather turf weeds such as chickweed, lespediza and clover.
Triclopyr is an herbicide for a wide array of the most common broadleaf weeds, including oxalis. It is reputed to have less of an odor than other broadleaf herbicides. It is often mixed in with secondary or tertiary herbicides to increase its effectiveness on a wider array of weeds.