Edge oxidation is the mechanism
Withered leaf is shaken or tumbled repeatedly so cells rupture along the margins while the centre stays intact. Oxidation then begins at the rim and works inward under the maker’s control. A finished oolong leaf held to the light often shows this directly — a reddened border around a still-green middle. The aromatic compounds associated with orchid, lilac and stone fruit develop in this partial, controlled window and are largely absent at both extremes.
The maker stops it by smell
The number of shakes, their vigour and the length of the rests between them are the main levers, and they are judged by aroma rather than by clock or instrument. This is why oolong varies so much between producers working with the same cultivar in the same place, and why the category resists standardisation in a way black tea manufacture does not.
Cultivar contributes a signature
Some of the floral character is the plant rather than the process. Tie Guan Yin carries an orchid-and-lilac aroma that substitutes do not reproduce exactly; Jin Xuan carries a natural creaminess; Phoenix Dan Cong bushes are classified by which fragrance they resemble, and those aroma types are stable enough to be a grading system. Process generates the aromatic window; cultivar decides what appears in it.
Roast buries it, deliberately
Floral character is the lightly oxidised, unroasted end of the category. Roasting replaces it with toast, caramel and mineral depth — which is a choice rather than a loss, and traditional Tie Guan Yin was roasted before the modern green style displaced it. Anyone who finds oolong floral and likes it should stay at the light end; anyone who finds it too perfumed should try a rested Wuyi rock tea.