Clumping fescue can be a pain when it makes its home in your lawn. Those unsightly clumps are notoriously hard to get rid of, and hand weeding rarely does the trick. To kill clumping fescue for good, you must treat it with an herbicide from March to April or September to October, when fescue grows the most vigorously.
Mow, prune or burn the clumping fescue as close to the ground as possible. This gets rid of dead leaves that are not susceptible to the herbicide and allows new growth of susceptible leaves.
Allow the clumping fescue to reach roughly six inches in height before you treat it.
Determine how much herbicide you will need. A few clumps can be handled with a hand-held bottle sprayer. For more widespread infestations, you will need to purchase a concentrated herbicide and a 1- to 2-gallon pump sprayer.
Mix the herbicide according to the manufacturer's instructions. This may be as easy as shaking a bottle sprayer or mixing a certain amount of herbicide concentrate and water for use in your pump sprayer.
Spray the herbicide directly into the middle of the fescue clump. Try your best not to over-spray and affect desirable vegetation. If you accidentally kill a few blades of your lawn, don't worry. It will grow back in a few months.
Wait a few days for the fescue to brown and die.
If the clumping fescue pops up again, wait until it reaches six inches in height before applying a second application.