Heat

The vascular system of a tree, which is responsible for transporting water and nutrients, and the cambium, which is responsible for diameter growth, lie just beneath the bark. Combined, the vascular system and cambium are usually less than 1⁄2 inch thick. Bark is a relatively good insulator, however, intense heat can easily damage this thin layer of vital tissues and cause severe injury or death. Trees with thin bark are more susceptible to heat injury on the stem, but even thick-barked species can be damaged.  Succulent tissues such as leaves and young shoots are particularly susceptible to intense heat. The living cells of these tissues can be killed by excessive temperatures, or rapid water loss through transpiration may exceed the trees capacity resulting in wilting or leaf scorch. This is frequently seen on low branches over parking lots. Avoid placing trees in close proximity to surfaces that absorb and radiate intense heat such as asphalt or dark rocks. Radiant heat from these surfaces can easily “cook” the living cells of the vascular system and cambium on a hot summer day.