Proper watering in the first year is the single most important maintenance factor in the care of newly planted trees & shrubs. Too much or too little water can result in injury. More trees & shrubs are killed by too much water than by too little.
Check new plantings often, they are perennials and are still establishing their root systems. Trees & shrubs drew most of their moisture from the root ball, make sure the soil remains moist (not soggy). The root ball can dry out in only a day or two. Water both the root ball (right around the trunk) and the surrounding area. Water deeply and then let the water soak in, encouraging new roots to grow deeper into the soil.