I love the change of seasons and my favorite autumn sight in Beijing is the transformation of the Ginkgo biloba (yin xing) trees as they prepare for a chilly winter.

In the next few weeks a golden ochre color will work its way from the outer edge of the tree's fan-shaped leaves toward the stem. The tree will stay a glowing mass of gold for a few days and then dramatically and simultaneously, the leaves will fall.

This picturesque scene is often accompanied by a far less romantic odor as the ripened berries from the female trees also fall to the ground. They emit an indescribably putrid smell due to a particular acid in their fleshy outer layer that is also found in rancid butter, vomit and body odor. That would explain it.