Continue mowing your lawn as it grows. Encourage a lush, healthy lawn by keeping it about 2-1/2 inches tall. Longer grass blades often mean a deeper root system, so your lawn holds up better during drought. Plus, taller grass does a better job of shading out low-growing weeds such as creeping Charlie, plantains, and dandelions.
If you have a cool-season lawn and didn't fertilize at the end of May, you can feed it in early June. But don't fertilize after the first or second week; it's best to let your grass slow down a little and get ready for summer.
May and June are good times to aerate cool-season lawns because the grass is actively growing. Rent an aerator if your ground seems very hard and the grass has a hard time growing. The looser your ground is, the better job your grass will do at crowding out weeds.