Fertilize Container Plantings
Plants confined to containers can't send out roots in search of nutrients, so we have to supply them regularly. Adding a slow-release fertilizer at planting time provides a steady supply of nutrients for several months. Or you can mix and apply a liquid fertilizer and use it weekly. Be sure to dilute the fertilizer properly -- more is not better. If plants dry out completely, rehydrate them first, then use the fertilizer solution the next time you water.
Replace Flagging Annuals
Pansies, lobelia, petunias, snapdragons, and other cool-season annuals can go into a slump in midsummer. Either replace them with heat-lovers, or cut them back in the hopes that they'll survive until fall, then bloom again as the weather cools.
Spend Half Hour a Day Pulling Weeds
Spend just a half hour ... surely you can find a half hour. Weeds really do sprout overnight and by next week they'll be towering over your zinnias. A visit to the garden before work or as soon as you get home can keep the weeds in check.
Keep Tomatoes Evenly Watered
Dark leathery spots on the blossom end of tomatoes is likely to be a condition called "blossom end rot" that's caused by uneven moisture. Mulch will help moderate the fluctuating moisture levels that nature provides, and it's not too late to spread some around your plants.
Avoid Using Sprinklers in Midday Sun
The best time to water the garden with a sprinkler is in the morning, second-best is late afternoon, worst is during the hottest part of the day. So much water is lost when using an overhead sprinkler on a sunny afternoon that you may as well pour it down the drain. Even better than a sprinkler are drip irrigation systems and soaker hoses, which slowly apply water directly to the soil and don't wet the foliage. If you do use a sprinkler, be sure to keep it on long enough to wet the soil to the root zones. This can take much longer than you think.