Mine is the black poplar. This is because it is a very tall yet elegant looking beast with the most beautiful fragrance you could imagine - truly the smell of its sap is quite something. Furthermore it is one of the UK's rarest native trees and is set for extinction in its 'wild' form by way of its complex (for trees) reproductive tendencies. I find this quite sad and feel more love for it as a result.
What's yours and why?