Recently I reported to you about a homeowner who wanted to plant a tree during the summer months.  I’m happy to report that he did, and following my advice, his tree is doing quite well.  He called the other day and asked if it is OK to lightly wet the foliage when he waters it on hot days.  I said yes, but not during the hottest part of the day.  Let me explain.  Syringing the leaves will help lower the air temperature around the tree, (as the water evaporates from the foliage), and reduce the chance of leaf scald.  My suggestion to him was to wet the foliage in the morning to avoid water drops acting like mini-magnifying glasses and burning the leaves.  Also, do not water at night as this may encourage disease, as the water droplets act as magnets and draw bacteria and fungal spores from the air.  As these droplets evaporate, the disease is on the leaf surface and can penetrate the plant thru the leaf pores (stomata).