Kathmandu, Sept. 12 -- Every spring Kathmandu turns into a city of flowers blooming with jacaranda and bougainvillea. People wait year-round to escape the otherwise dull and dusty concrete landscape with a vibrant streets of purple, red and green.

But very few people know that these beautiful roadside trees and their colourful seasonal flowers are ill-advised for our climate, and can increase road hazard.

Trees shelter us from sudden downpours, and during hot summer days, we seek their refreshing shade. In fact, they reduce the temperature of the asphalt surfaces beneath them by as much as 15deg Celsius.

Trees purify the air by sequestering carbon dioxide and giving off oxygen, they remove harmful gases and particulate matter. They imp...