Watering by hand is the most effective and efficient form of landscape watering.
Effective because the water is applied directly to the soil over the roots and efficient because, in the case of trees, the water is applied over the most important part of the root system — the canopy drip line.
The only downside to hand watering is if you apply so much water that the soil can’t absorb it. That said, there is a right way and a wrong way to hand water.
Standing in one corner and using a hose with or without a nozzle to spray water into the air is not proper technique. Like a sprinkler or in-ground spray head, most of the water is evaporating into the air, not hitting the ground in a consistent manner. On the other hand, pointing a hose downward and standing in one spot for 10-20 minutes is not correct either.
Proper technique involves the use of a hose-end water wand or similar device to water an area for about 10 to 12 seconds before slowly walking to the next area. Then — and this is important — repeating the process over the same section once more. How fast should you walk? Just use the Mississippi method to count seconds… one Mississippi, two Mississippi, and so on.
If it has not rained for three weeks, you may have to cover the area three times. This allows for slow infiltration and deep percolation of the water.