Sugar, red and Japanese Maples: You can drive up and down America’s east coast to enjoy their fiery pyrotechnic shows each fall. Along the way, you may want to hop out of the car, take a deep breath and hope you catch a whiff of the katsura tree’s sweet scent.

“I can barely smell it, but as people walk through my garden, they shriek, Cotton candy!” said Ken Druse, a gardener and author of “The Scentual Garden,” a book about how humans smell and process scented plants.

Autumn seems to belong to pumpkin spice, and odors are often overlooked when it comes to fall foliage. We rave about how leaves die colorful deaths and rarely discuss how their scent changes with old age. But right about now in Mr. Druse’s garden and elsewhere around the country, the leaves of katsura — which can be found all over New York City and in many other parts of the United States — are just beginning to turn. The katsura is also called the caramel tree. In Germany, they call it “kuchenbaum,” or “cake tree.” And if you’re able to pick up its scent, you’ll see why.

Known scientifically as Cercidiphyllum japonicum, the katsura tree is native to Japan and China. Fossil records suggest it once grew widely in North America and Europe before going extinct in the cold Pleistocene epoch. It returned to the United States around 1865, when an American diplomat in Japan shipped seeds home to his brother in Manhattan, who operated a family nursery.