Per MPLS park & rec:
[Established] Trees Need an Inch of Water Every Week — Trees are thirsty all the way through fall
“Minneapolis’ boulevard trees still need an inch of water every week throughout the summer and fall. Extremely dry conditions followed the spring and early summer rainfall that drenched the city and caused significant damage, and the heat and lack of precipitation are causing stress on the City’s urban forest. Lack of water can make trees vulnerable to insects and disease and cause permanent damage to young and old trees alike. Trees up to five years old are especially susceptible. In any week that it rains less than one inch, yard and boulevard trees need to be watered. The Park Board plants and mulches boulevard trees but relies on residents or businesses nearby to water them.”
“An effective way to water a tree is to turn on a slow stream of water (just so the hose is weeping) for a few hours. Watering in the evening after dinner time is most effective since it minimizes evaporation, and trees tend to take most of their water during the night.”
During and leading up to hot days (we’re supposed to get the heat on Sunday) if you have an established tree, employ a soaker hose turned on low for approximately an hour during early evening daily. This is sufficient to prevent the tree from becoming stressed. If the tree is already stressed, consider watering in the early morning and evening. In cooler weather you won’t need to water every day.
“Watering one tree weekly costs only about $3 for 23 weeks, or for the entire summer / fall season. For people who lose track of when they last watered a tree, a good way to remember is to water trees on the same day trash is picked up.”
*Be sure the mulch around your tree is pulled away from the trunk. Packed mulch against a trunk can cause decay, rot, and introduce other disease or pests.
Where to water:
Young trees (less than 2-inch caliper) — Treegator® Original Slow-release Watering Bag
Established trees — measure the trunk at 4.5-ft. from ground. Multiple by 1.5. Measure that far out from the trunk to get the “dripline” and place the soaker hose around the tree at that location.