The best method of watering trees and shrubs is with a soaker type hose or to use the end of the hose to insure that the roots of the plants receive a thorough watering. It is best to keep water off of the foliage because it can cause plant diseases.
If you have a drip irrigation system you have to be sure that the soil has adequate moisture, as drip irrigation does not do a good job once the soil has been dried out. Check around the plants to insure that they are receiving the right amount.
Buy a moisture meter. This inexpensive device will allow you to check the moisture not only in your shrub beds, but also in your lawn, house plants, and vegetable garden. A moisture level of 50% or greater is recommended.
Watering After Planting. Water must be applied during the first growing season. Wet the soil thoroughly enough to soak the entire root system at least once every 5 days during drought conditions and possibly less often under milder temperatures. Rainfall will not substitute for direct application of water to the rootball, however, it may allow you to lengthen the watering interval a couple of days.