It shall be unlawful, as a normal practice, for any person, firm or Town department to top any tree located on public property. "Topping" is defined as the cutting back of limbs to stubs larger than three (3) inches in diameter within the tree's crown to such a degree so as to remove the normal canopy and disfigure the tree. Trees severely damaged by storms or other causes, or certain trees under utility wires or other obstructions where other pruning practices are impractical may be exempted from this section at the recommendation by the Tree Board to the Town Council.