Portland’s scents are among the world’s finest and freshest. Because of the doughnut chain next door, my neighborhood smells like fresh rising dough, confectioners’ icing, and fruit fillings on its best days, shifting savory at night thanks to a score of breweries and coffee roasters. The neighborhood’s base notes shift seasonally, now emitting petrichor, dried leaves and windy evergreen. If I were blending a fragrance for downtown Portland, I’d layer notes of ivy, river water,...