Place it just after the birch first appears on screen, then let the Anime Wow sound answer the reveal, keeping it as the central claim in the middle of the sequence.
このサウンドについて
My Birch is a 2.6-second sound effect centred on its title phrase, presented as a brief personal claim about a birch tree. It gives a playful, slightly possessive feeling, like someone proudly naming a tree as their own, and works best as a small, knowing nod between people who share the joke.