Renew Mulch Around Tomatoes and Peppers
High heat and insufficient water can cause tomatoes and peppers to drop their flowers, and uneven watering can cause the blossom end of tomato fruits to rot. Keep the soil mulched to conserve water.
Sow Late Crops
There's still time to plant fall crops of beans, beets, broccoli, carrots, Chinese cabbage, kale, lettuce, and peas. Plant lettuce in the shade of tomatoes or other tall crops to keep it cooler, or use shade cloth.
Raise your mower blade to cut at 3 inches to allow the grass to better withstand the heat. If you cut too low, the blades will rapidly turn brown. Keeping the grass longer will also help shade any weed seeds and reduce their germination.
If your annuals are looking peeked, they may bounce back with a good dose of fertilizer and some trimming. Pinch stems back by about a third, and remove any dried out stems right at the base. Also give container pansies and lobelia -- which tend to succumb in late-summer heat -- some shade in late afternoon.
Salicylic acid, or aspirin, has been found to boost plant growth, so give it a try. Dissolve 3 aspirins in 4 gallons of water and spray plants. Or take two of the same type of plant and spray one and not the other and then compare results.