a sharp symbol is ++ stacked on top of ++ So C ++ ++ becomes C#

Phonetically, It is C sharp because it sounds cooler than C hash or C pound.

The tree would drown.
Trees require evaporation through the leaves to draw nutrient enriched water from the roots through the trunk to the leaves. Which then evaporates and causes the process to be continued. They also require Carbon for the photosynthesis process, which trees absorb via the leaves in the form of Carbon Dioxide.