It is not the length of time but the volume of water delivered. Plants need deep watering, to two feet, at the drip line and then when needed. Check this by driving a stick down to that depth after watering and removing it to see how far the water penetrated. With this method you will determine when and how much water to use. I think you will find that you need to water twice a week now and three times a week in the heat of the summer.

Mullenium,

Petzold gave you good advice on watering deeply. Another thing to check is how many emitters you have on each plant and how much water they deliver. One gallon-per-hour (gph) emitters are common and when landscapes are installed each plant usually only has one.

Keep in mind that one gallon of water will moisten about 1 cubic foot of soil. While that may be enough for small plants, larger shrubs and trees will need much more. If you have 1-gph emitters, I'd recommend you set your timer to run at least 2 hours which will not only moisten the rootball but surrounding soil as well. The longer you can keep moisture in the root zone the less often you will need to water.

This time of year watering once a week for 2 hours should be adequate. As temperatures rise above 90 degrees once every 5 days should be good. By June and through the summer apply water once every three days. When nights begin cooling off in September, you can extend the interval in between waterings again.

Deep and infrequent is the key. Soggy soils will deprive roots of needed oxygen and promote bacterial and fungal rots especially in summer.

Here is a link to watering guidelines in the metro Phoenix area.

Here is a link that might be useful: Landscape Watering Guidelines

They just installed the landscape in my backyard and set it on the same zone as the front yard plants which have been growing for a couple years. Them setting it to 41min each day makes me think this is for the new plants to get acclimated.

so what do you think is a good time / day schedule considering the new plants in the back are now on the same zone as the established plants in the front, maybe an hour every 2 days?

each shrub has a single 1gph emitter and each tree has 2x 2gph emitters.

since I dont want to over water, maybe an hour every 3 or 4 days?