The unmistakable fragrance of the linden tree (genus Tilia) is everywhere in Berlin. It's summer, and lindens are teeming with flowers (and sap). At night, I open all the windows and breath the rich aroma of the linden blossoms. For a few months a year, the Berlin air is scented with the sweet perfume of the linden. It's a welcome change from the auto exhaust and cigarette fumes.