When I look at these pictures, I can practically smell them! And my hope is that you will take my advice and go smell for yourself. Because no one can be said to truly know the ginkgo without experiencing the aroma/stench of the seeds right about now.
Ginkgo biloba is a dioecious species, with separate seed-bearing trees and pollen-producing trees. Sadly, all ginkgo trees sold in the horticultural trade are pollen-producing trees (created by cloning other pollen-producing trees). This means we typically miss out on the experience of meeting up with seed-bearing ginkgo trees. Not so at the Arnold Arboretum, where most of our ginkgo trees were grown from seed. Such trees turn out to be 50-50 male (pollen-producing) and female (seed-producing).
So, what makes a ginkgo seed so pungent? The answer is lots of butyric acid in the yellow fleshy seed coat. This is the same chemical that dominates the smell of rancid butter and vomit. And while we may find this unappealing (understatement), long ago, there were animals that viewed the fleshy coat of a ginkgo seed as haute cuisine. As with most fleshy seeds and fruits, the embryo (future seedling) is housed within a very hard shell that protects it as it passes through the gut of the animal that has eaten it. A good deal for all, as the seed gets safely dispersed from its mother while passing through the gut—and the animal gets food as it digests the fleshy outer coating.
For an intense ginkgo seed experience, head over to the Walter Street Gate to a nearby 1928 accession (16439*B; left image), dive into the wonderful yew trees and hang around at the base of 16439*B for a few minutes to take in the magnificent gold of fall leaves (upper right, with one seed), and the overpowering stench of fall seeds (lower right). You will be glad you did!