Why can fallen ginkgo seeds be a hazard on paved surfaces?

Fallen seeds from female ginkgo trees can create a slipping hazard on paved surfaces because of their fleshy outer covering. When these seeds ripen and fall, the decomposition of this outer layer produces a highly disagreeable odor, often compared to rancid butter, and the resulting mess can make walking surfaces slippery. Due to these characteristics, female ginkgo trees are generally less favored for ornamental garden planting.1