India, June 25 -- This June afternoon, the two giant bougainvillea near the duck pond in Lodhi Garden are in rich bloom. Their pink canopies rise above the garden, visible through the summer haze. Blossoms are drifting down from the branches, carpeting the ground with papery petals.

Only a few weeks ago, these trees were completely flowerless. That was puzzling, because their summer blooms are usually enduring. Whatever, now the branches are once again in pink.

The trees being so picturesque, the benches beneath the trees attract visitors throughout the day. This afternoon is no different despite the sweltering heat. Two lovers are sitting quietly on one bench. Another is occupied by a family of five-a man, a woman, an elderly woman, an...