It is always important to keep new plantings properly watered. It is even more important during a drought. New plantings should be watered deeply two or three times a week as opposed to adding a little water every day.
Deep watering encourages deep root growth. A good way to accomplish deep watering is to leave a small berm of soil around the plant. The berm should be at least as wide as the plant so that, when filled, the water infiltrating the soil is wider than the root ball.
This will encourage roots to grow outward from the plant. It is a good practice to water plants in this way for two growing seasons when drought conditions exist.