India, March 6 -- The Wednesday evening is leisurely settling down over Lodhi Garden. The day of Holi is drawing to a close. High in the air, a cloud of pink appears to hang suspended. It resembles the gulal of the festival. But the colour is not powder thrown in celebration. It comes from the flowers of a tree.

The flowers rise on long, leafless branches of a tree standing at the edge of the park's central lawn. For most of the year, this tree draws visitors for simpler reasons. Its leaves cast a broad, restful shade. Beneath it sit green benches from which one of the garden's most familiar views opens out: a panorama that includes the Sheesh Gumbad and Bara Gumbad. People pause here to sit, to WhatsApp, to read books, or to look at the...