Question
We have a large globe willow in our front yard which we suspect is more than 20 years old.  We have read that these trees are native to the Colorado region; however we live in the high desert of Northern Nevada.  The globes are common around the neighborhood.  Our tree has been beautiful and healthy until the past two seasons.  It has lost so many branches that it no longer has its puffball appearance, and the leaves are yellowing rather than the bright green they should be.  Several branches are bare and appear to be dead.  We love this tree and hate to lose it, as it is the focal point of our front yard.  What can we do to restore its health and beauty?

Answer
I would try fertilizer. Use 10-10-10 fertilizer at the rate of 1 lb per inch of trunk diameter scattered around the tree and watered in good. Sometimes over watering will cause the tree to turn yellow but you did not mention watering so this is more than likely not the case.