Though trees are much more resilient than flowers or grass, you still need to pay attention to how much water they're getting, especially as hot weather hits. One thing to keep in mind: Trees get much of their water from their massive network of fine roots, which quickly get saturated, so just dumping a ton of water at the tree's base doesn't cut it because most of will run off and not sink down deep into the roots. Instead, use a dribbler head on your hose to supply a slow, steady dosage. And remember to move the hose around some to make sure the whole root structure thrives.
