Chisago County Master Gardener
The long dry spell has me spending lots of time watering. The most noticeable drought effect is with birch trees.
All of my river birch and white spire are well-established, at least 15 years old, but several are covered with yellow leaves.
Severe drought stress can cause branch dieback, starting at the tips. Luckily, I’m not noticing any dieback.
Dying birch leaves and branches can also be caused by iron chlorosis, when roots are unable to absorb iron from the soil, but the most likely cause is drought.
To properly water a tree, make sure the water reaches the feeder roots at the drip line, below the widest part of the canopy. This could be several feet from the trunk. Using a sprinkler, water until the soil is moist at least 6 to 8 inches below the surface.
For more information, visit http://www.na.fs.fed.us/SPFO/pubs/howtos/ht_birch/ht_birch.htm.