Ginkgo biloba has been popularly used as a dietary supplement to prevent memory loss, though only slight evidence exists for its effectiveness (for an awesome interactive visualization of the data supporting various dietary supplements, see Information is Beautiful). But there is more to ginkgo than dubious supplementary status. Ginkgo is a relict.
The division of plant species that Ginkgo biloba belongs to, Ginkgophyta, was once full of species; 150 million years ago, they flourished in the temperate zones of the world. But now there is only one. In the Ginkgophyta, there is only one class (Ginkgoopsida), in that class only one order (Ginkgoales), in that order only one family (Ginkgoaceae), in that family only one genus (Ginkgo), and in that genus, a single living species. All of its close relatives have long since died out. No other Ginkgoales are known from the fossil record after the Pliocene, 2.5 million years ago.
Now this living relict is a favored ornamental, common to the storied grounds of universities and large estates. But there’s something you should know about ginkgos, before you go planting them willy-nilly. Walk around a classy university campus in late summer or fall, such as the University of Chicago, and you will quickly notice the unmistakable stench of vomit. Over-indulgent undergrad, you might guess. But rather, the fruit-like ovule produced by a female ginkgo contains butanoic acid which reeks of rancid butter or vomit once dropped. Careful landscapers make an effort to plant male trees, though they are indistinguishable on sight from females until maturity.
When Frank Lloyd Wright bought his home in Chicago’s Oak Park neighborhood there was already a few small ginkgos growing in the garden. At least one tree stands there still and its influence is prominent, both to the landscape of the historic home and in the work of its previous tenant. Every summer, tourists and architecture enthusiasts flock to the beautiful home and museum. And in the summer, every morning, the museum staff sweeps the putrescent fruit out of the courtyard, so as not to disturb visitors.