Usually, trees and shrubs are considered to be fully "established" after 3 years, when it can be assumed that they have healthy and widespread root systems, and can rely on the moisture naturally present in the ground for their needs. Before that, it is assumed that their root systems are still too small to meet their needs.

You need to give the equivalent of an inch of rain per week, whenever the soil is dry down about 2 inches, for the first 2 years. You can slack off a bit in the third year, but if there is no rain for about 3 weeks, then water again until it rains. Water slowly, so the water gets to the bottom of the root ball and doesn't just run off.

That is a lot of water. We have a whole new landscape. Thanks Dibbit.

a fairly good indicator.. is when they grow to the established annual growth rate for the plant ...

e.g. a plant that should be growing one foot per year .... might not achieve that growth rate.. after transplant ... for 2 or 3 years... growth rate is a function of the root bases ability to maintain that which is above ... and keep in mind... potted hyperfertilized stock MIGHT do such after transplant... and then regress in the second year.. depending on how well you care for it.. which involves proper deep watering as noted in the first reply ... there is no way around inserting your finger to the second knuckle and determining how water moves through the soil in your garden ... what works for me.. may or may not work for you ... i dont care how much or how long you water.. if it isnt getting down to the root zone.. it just isnt proper

ID your plant.. with the latin name.. take such to google.. and find out how well it should grow.. and maintain conditions that will allows such.. until such time as it achieves such ...

ken

Lainey, if you haven't mulched already, do so - it will help keep the soil cooler and keep whatever moisture is in the ground there instead of evaporating. Any good mulch will do - just DO NOT lay down plastic or landscape fabric under the mulch - it is ineffective and ugly after a few years. Mulch as widely as possible - at LEAST 3', and wider if you can - no deeper than 4" max., and put NO mulch in the inch or so next to the trunks.

Yes, it's a lot of water and more time, but think of the beauty you will have down the road. Don't rely on the lawn irrigation system to water shrubs or trees for the first few years, as they are set up for shallowly rooted grasses, and don't run for long enough to go deep enough. (Once the plants are established, their root systems go widely enough into the grass that they can cope.) Usually, if you try to set the irrigation system for longer, you just get wasteful run-off. If you can set up spot watering at individual plants from the system, OK, but don't have them on an automatic timer, as individual checking will still be needed. And you will need to check periodically to be sure each plant is really getting enough water.