The roots of a young tree are mostly located near the trunk and grow 12-18 inches below the surface.
A young tree needs 10-15 gallons of water per week. Slowly soak the area near the base of the tree 2-3 times per week with 5 gallons each time.
You can use:
• A hose on a slow trickle
• A soaker hose
• The bucket method belowThe Bucket Method:

1. Collect water in a bucket while your shower warms up.
2. Drill a small hole (1/8″) near the bottom of a second bucket and place it near the trunk of your young tree.
3. Fill second bucket with the shower water you saved. The water will slowly drip into the soil and keep your tree healthy.

Source: Sacramento Tree Foundation