Since a newly transplanted tree or shrub has not extended its roots into the existing soil, adequate moisture needs to reach the root ball. Soil type and the amount of rainfall govern the amount of watering necessary. On most well drained soil, one inch of water per week throughout summer and fall is required to establish and maintain good growth.
Turn your hose on at a slow trickle and leave running (moving hose around to wet all sides) long enough to saturate the planted space and surrounding soil. Water bags are also a good way to assure slow deep watering. Be cautious if you have heavy clay soil. You may need to water less often. Check moisture in the soil before you water!
Apply a three to four-inch layer extending from the base of the plant out past the drip line (end of the branches). Do not let the mulch rest against the trunk of the plant. All plants benefit from mulch, because as the mulch breaks down, it provides an excellent growing medium for roots, and acts as a slow release fertilizer. Mulch will also help conserve moisture, moderate soil temperature, eliminate weeds, and protect the trunk from mechanical injury - especially weed whips and lawn mowers.