Our wet and cool spring was good for extending the bloom periods of many shrubs, trees and perennials. Years that we have warmer temperatures often result in flowers only lasting a couple of weeks. This year things bloomed for several weeks. On top of that, many plants bloomed much later than they normally do. Lilacs, for instance, showed their colors after Memorial day which is unusual. The wetness and moderate temperatures encouraged healthy vegetative growth and delayed the need to begin supplementing water to established plants. Personally I didn't feel a need to start my lawn sprinklers until near the end of June.
Now we're working our way through a major heat wave and facing the probability of a long dry summer. As previously alluded to, established plants normally don't need appreciable extra water. They obviously shouldn't be allowed to dry out completely but periodically giving them a deep soaking is, in most cases, sufficient.
New plantings, on the other hand, are highly susceptible to low moisture conditions and, if allowed to dry out, will die within a short time. Even if they do survive, their appearance can be substandard for an extended period.
For new plantings, ensure that the entire root mass gets soaked with each watering. Monitor soil moisture and water as called for. In a short time, you should be able to determine a watering schedule that will help plants grow their roots into the surrounding soil bringing them closer to being "established".