For a new planting of a 2 1/2 inch diameter Autum Blaze maple, how many gallons of water for each of three waterings per week ?

I set a hose on the root ball and set a very slow trickle for 15-20 min. If you are seeing runoff the soil is adequately watered. Remember that you will need to water until the ground freezes but you can lessen the frequency of watering as the temperature drops.

10 gallons for every 2.5 inch of trunk diameter water them 2 times per week

3 gallons