Don't neglect the watering of any young fruit trees especially if wall-trained, the most common reason young Apple, Pear and other Fruit Trees fail to thrive is due them being parched in their first summer!
You wouldn't expect your patio plants to survive the summer without water - so treat all your young plants to the same care and attention!
Unless it is really baking hot a really good soak to the roots of new trees a couple of times a week is all that is necessary and will pay dividends for the future. If there is a real hot spell they may need watering every day depending on their position.
Avoid the 'little and often' approach to watering, all this does is encourage weak roots near the surface, one really good soak every few days will allow water to penetrate deep into the soil and the roots will then go downwards to seek it out resulting in a much stronger and healthier root system.