The biggest favor you can do for your plants during hot summer weather is to give them the moisture they need. While you don't want to leave plants thirsty, you also don't want your water bill to rival your mortgage payment. Here are a few answers to the questions people often ask about watering.
How can I tell if my plants need water?
Newly planted ones generally need more than those that are established. Do they look stressed? Are they drooping or losing leaves? Feel the soil around them. Don't water unless the top 2 inches has dried out. How often you'll need to irrigate depends on many factors, including weather, soil, and plant requirements. When it's time to water, do so thoroughly. It's important to remember that infrequent, deep watering is better than frequent, shallow watering because it promotes deeper root growth.
When is the best time to water?
Start the day off right. If plants need water, early morning is the perfect time to do it. This will carry them through the heat of the day. Late afternoon is not as good because of increased water loss through evaporation. Also, if leaves do not have time to dry, the cooler evening air can encourage fungal growth.