Watering a new tree is the most important thing that you can do for it. Even if it has rained, it is still important to give your tree and deep soaking.
Most people stand with a water hose and spray the top of the dirt and watch the water flow downhill away from the tree, and think that they watered their tree. You must give your tree a deep root watering in order to call it watered. Here is the best technique for maximizing the effectiveness and saving water.
Turn your hose on a very slow drip and let it stay on the trunk of the tree for at least 8 hours at a time. Do this no less than 3 times per week. More often in the heat of the summer.
If you want to invest in a Tree Gator, a 20 gallon slow release water bag, that will work too. I recommend filling it everyday.
Happy Watering