India, March 10 -- Across the megapolis, some trees are letting go of their leaves, while others are bursting into colour. In March, Delhi stages a drama of opposites. Consider a peepal in Punjabi Bagh. Every leaf has fallen. Sunlight is passing cleanly through its branches. On the other hand in Malcha Marg, a bougainvillea is ablaze with new pink. During this time of the year, Delhi's many avenue trees stage an annual retreat, shedding foliage ahead of the long, dry summer. The peepal is among them. By discarding leaves, such trees reduce water loss through transpiration. Bougainvillea, meanwhile, is doing the opposite. It flowers through most of the year, but peaks between March and May, as confirmed by a Lodhi Garden gardener. These two ...