If you have planted apple trees this year then, now as summer reaches its peak, you should pay close heed to the following advice. Water well and water often. Making sure a young apple tree is not short of water and its first and second years is probably the most important thing you can do to ensure that trees long-term success.
In the first year and apple tree will be pushing out roots searching for water; if it encounters dry soil the tree will not prosper. You really cannot be too generous with your watering regime. Obviously if the roots are actually swimming in a permanent puddle then you have overdone it. But that aside you should water more often than you think. And when you water, water generously. A single small watering can full will simply soak the top inch of soil. Two big watering cans full are The minimum you need To get the liquid down to where the tree needs it.
About twice a week I pour on lots of water and let it soak it down. About 5 to 10 gallons goes in with the soil is dry. I am constantly looking out for leaves that lose their Sheen; early sign of drought. Leaf drop is another more serious sign of drought stress on an apple tree.
In the years three and four you must still be very vigilant but perhaps can ease back ever so slightly without worrying. In year five and beyond the tree should do okay if left to its own devices and will probably not die from lack of watering. However for good cropping you do need to keep watering your trees.
Of course there is a flip side to this. It is possible to kill a young tree through overwatering. If the roots are sitting in a permanent capital they cannot get the oxygen they made and the tree beginning to rot. To avoid this don’t water every day but water as I said twice or three times a week but make sure you give your tree a good drenching.
Use your fingers as well as your eyes. Touching the soil is a great way of understanding whether it needs watering. Trust your judgement and experience and listen to what the tree tells you it needs. If the tree looks like it needs watering it probably does.