Aerate and overseed your lawn. Mow your lawn a little lower than normal. Use a core aerator (which pulls the little plug out of the ground). Make passes perpendicular to each other. Broadcast the seed right over the lawn area. If you can, rent an overseeder. Either way will work. Core aeration increases the air and water exchange in the top of the soil profile, loosens compacted soils, thus helping to build a denser root system.
Apply lawn fertilizer.
Apply lime to your lawn if necessary.
Continue mowing weekly. It is best for the lawn to not cut grass below 3 inches tall. It is also better not to bag grass clippings. Leaving the clippings on the lawn saves work, adds organic matter and nitrogen to your soil, and does not contribute to thatch build-up.
Do some light pruning on shrubs to get some of the summer growth off of them. Tidy up a bit, but be careful pruning shrubs that bloom in the spring.
Planting, dividing up, and transplanting are great ideas as the weather cools off.
Harvest the last of your summer vegetables and clean up your vegetable garden.
Plant cool weather vegetables this month for the best crop.
Look out for spotted lanternfly adults.
Check yourself and others for ticks. Here is a great resource in our area for information on ticks and tick-borne illnesses.
Look out for many spiderwebs as you walk through your yard over the next month. The spiders are busy feeding on pests!
Spruce up your property for the fall with some colorful mums. If you want to save the mums for years to come, plant them in the ground by the end of September (the sooner the better) and mulch them well to give them the most time and protection to get established.