3 ideas
The reader narrows the candidates by elimination, starting from the most reliable year-round feature, the leaf, and confirms with flowers or bark when present. Taxonomy comes last, as the answer, not as the entry point.
When New Delhi was laid out as the imperial capital, its planners assigned trees to avenues so that a whole road carried one species, such as jamun, neem, arjun or imli. The chosen trees favoured dense shade and a tidy, evergreen look suited to a monumental city. Because of this, the city's street trees today record colonial design decisions, and a road's identity can be read from its trees.
The Delhi Ridge, an outcrop of the Aravalli hills, originally held a native thorn-scrub forest of species such as dhau and khair. Prosopis juliflora (vilayati kikar), brought in under British rule to green the dry, rocky ground, spread aggressively and now dominates much of the Ridge, suppressing native regeneration. What looks like 'natural' forest in the city is largely a monoculture of an introduced plant, so restoring the Ridge means removing a tree, not planting more.