Many Minnesota trees were already suffering from a very dry fall in 2011.  The unusually high temperatures and lack of snowfall this winter will add more drought stress for many trees.  Some additional watering this April will be needed for many trees to help them restore their health.  Soils should be kept consistently moist, but not saturated.  Plants in sandy soils will require much more watering than plants in heavy clay soils.  Over watering (specifically in clay soils) can be just as damaging as under watering.  Most trees will need 1 gallon of water per week for each inch of trunk diameter.  For example, a 5” tree needs at least 5 gallons per week either from rainfall or supplemental watering.