How Often Should I Water My New Tree?

How often should you water your new tree/plant? The answer really depends on the plant, where you live, what time of year it is, and your weather. 
Some trees prefer water sometimes but mainly a little on the drier side, while some require a deep soaking quite often. Bald cypress is one tree that can actually grow and live in swamps, which means the tree roots are underwater! Some other plants such as a emerald green arborvitae prefers a deep watering every now and then and does not appreciate “wet feet” (constant wet roots) or root rot will happen and it will die. 
It is very important to understand the exact needs of the plant you are wondering about - typically a quick google search will help you know how much water your tree prefers. There are also many other things your tree may like or dislike such as sun, shade, cold temps, hot temps, highs acidic soil, etc. but for this question we will go over how much to water your tree. 
Now, assuming you have or will do your research in figuring out how much water your tree might need, I will give the basic rules that applies to almost all newly planted trees and plants. 
Week 1 - deep watering daily
Week 2 & 3 - water every other day
Week 4, 5 & 6 - water every 3 days
Week 7, 8, 9, & 10 - water every 4 to 5 days
Week 11, 12, 13, 14, & 15 - water once per week
Week 16+ Water once per week when conditions are dry. If a good amount of rain has come - typically watering will not be needed. It is good for your tree/plant to receive one deep soaking which is better than a few light watering sessions. 
After a year or two when a trees roots become more established, you may only need to give water during major heat in the summer or in times of drought. 
More plants/trees are killed due to overwatering than those that are under watered! Overwatering will cause root rot in most species and a tree cannot typically recover from that. Trees can however, typically recover from dry times with a little bit of extra love and water when needed. 
Don’t be afraid to stick your finger down in the dirt near the roots of your tree a couple of inches. Is the soil super dry? Is it super moist? Or is it cool and lightly moist? Your mostly want the soil at that cool lightly moist spot, you normally only want to water again once the soil gets close to being dry again.