You can also spray the invasive day lilies with a nonselective herbicide such as glyphosate to kill them. Dig out the roots once the tops of the plant have turned brown. ... The day lilies growing in your new lawn should fade over time with regular mowing.

Does Roundup kill lilies?

It often takes two or three attempts to completely destroy lily-of-the-valley by digging. The herbicide glyphosate (Roundup) is another control option. Glyphosate is a non-selective, systematic herbicide that destroys virtually all plants onto which it is applied. However, lily-of-the-valley is a very tough plant.

How do you kill weeds in daylilies?

Protect day lilies with cardboard or a similar barrier, then spray all weed parts with a ready-to-use 2 percent glyphosate solution on a still, dry day, or use according to the manufacturer's instructions. Don't remove the cardboard until the weedkiller has dried. Systemic herbicides kill weeds in two to three weeks.