Keepitlow:

After settling in newly planted trees with water, I never water my fruit trees. But I do mulch them heavily, especially early in their careers, and the addition of organic materials on the surface translates to increased moisture-holding capacity beneath.

I live in Northern Virgina, where summer rains and thunderstorms are usually adequate for even young trees, but once established for a year or so they are capable of finding adequate moisture on their own even in the dry periods of up to 4 weeks that we occasionally experience in July.

Of course, a lot depends on your soil and your sub-soil; mine is pretty good. But, in general, I favor underwatering of fruit trees rather than overwatering.

Don Yellman, Great Falls, VA

So much depends on your local weather and soil, not to mention the tree type. Where I live, I have sandy loam soils and a virtually rainless summer. However, the winter and spring rains reliably saturate the soil to field capacity. This soil drains well but there is a reliable source of moisture at 18 inches deep and below. Not lots of moisture, but enough for plants to draw on, and it gets replaced constantly by capillary/wicking action from deeper below. This is how our wild blackberries grow foliage and juicy berries with no rain. Not to mention the trees and other perennials.
I generally water my newly planted trees liberally for the first year, less for the second year, and maybe a bit on the third year. None thereafter. It's quite possible I'm overdoing it, but I figure better safe than sorry.

It depends on your climate, soil and rainfall.

With the rainfall we tend to get I water weekly through the summer the first year. Rarely the second year (maybe monthly). Only during drought after that.

But I've only had to water my new trees once and grapes a couple of times so far this year because it's always raining.

Rootstock can also be a big determining factor.