When I planted conifers close to my trees, I was given the advice to put in drip irrigation for them and use it for the first few years, at least once a week a good soaking. Once they were established, I haven't irrigated at all and they have done beautifully through several hot dry summers. From what I understand, it's the first few years that are critical for watering for conifers.

Unlike tozmo1, I listened to people who told me that I didn't need to water the second year. All the central leaders died on Thuja planted near maples and a birch. This year, I installed drip irrigation, and they did not totally recover but they are all bushier and greener again.

Thank you Tozmo1 and Addison! The guy at one of the nurseries I bought a tree from told me to let my hose drip slowly for 20 minutes next to the tree. Would that be comparable to drip irrigation ya think?

What I did is to run tubing with drip emitters to the thuja, and, as it happens, a bunch of Rosa rugosa--not the tree. If you haven't looked into it, the tubing is pretty cheap and so are the emitters. It's not like buying a long length of hose and sprinklers... Until the drought came, I was giving the roses 1/2 gallon of water every couple days if it didn't rain for a while, and most of them got big and bushy and green. Thuja, I was giving 1 gallon. And they were recovering nicely... Other people seem to think that roses need "deep" irrigation less frequently. That advice has nearly killed my roses in the drought.

I agree, look into the drip irrigation. The difference between the drip irrigation and a hose drip (which I do for my dogwood when it gets droopy) is that the tubing with emitters has lots of places the water escapes (you encircle the tree) so 20 minutes of drip irrigation is multiples of a single hose drip. But if the hose is all you can do, you want to place the hose at the highest ground level at the tree's drip line, not right next to the trunk of the tree. Oh, and set a timer in the house or on your phone so you don't forget to turn it off. :-)