Drain saucers and any other sources of standing water where mosquitoes can breed. Dump birdbaths and pet water dishes and replace with fresh water at least twice weekly. There are several commercial products available to kill mosquito larvae in ponds; follow the label directions carefully to maximize their effectiveness.
Stop Pinching Mums and Asters
If you've been pinching back fall bloomers such as mums and asters, stop now so the plants will have time to develop flower buds. If you haven't been pinching, consider doing so next year because it promotes better flowering on these plants.
Provide Mid-Afternoon Shade
Strong midday sun will cause many plants to wilt, even if the soil is plenty moist. If possible, move container plants to a location where they'll get light shade in midday and early afternoon. Check soil moisture before watering; wilting can be caused by several things, including root rot from overwatering and other root damage, as well as high temperatures and hot sun.
Fill in Perennial Beds
Observe your perennial beds and jot down when there's a lull in flowering. Then look for plants that will bloom during that time. With careful planning, perennial beds can be in flower all season long. As you drive around your neighborhood, take note of garden plants you like; if the plants look healthy and vigorous, they're probably well adapted to your region. Consider carrying a camera and taking snapshots, noting the dates the photos were taken. You can then identify them using a reference book or consult garden center staff. Use the dates to help you work the plants into your landscape plan to fill in any gaps.
Plan for Vacation
If you'll be away from home for more than a few days, take steps to keep container plants healthy. If possible, have a neighbor water plants daily or as needed. If that's not an option, move containers to a shady location and water plants thoroughly before you go. Group small containers together and set in a shallow basin filled with an inch or two of water. Self-watering containers are a good choice if you travel frequently during the summer.