Ginkgo trees at Hokkaido University, Japan; image courtesy of 柴田拓, via Wikimedia Commons

At the right you see one reason Ginkgoes are so well known: They make pretty trees along streets, where they tolerate air pollution. Also, they're famously medicinal.

All that and more, from their propagation to their contribution to art, is well covered at The Ginkgo Pages website. Here, we're doing our backyard naturalist thing.

Pollen cones of Ginkgo biloba; image courtesy of Marcin Kolasiński of Poland, via Wikimedia Commons

Ginkgoes, Ginkgo biloba, are gymnosperms, but they're very unusual ones. Usually we speak of gymnosperms as producing cones, not flowers. Male Ginkgo trees -- the species is "dioecious," with each tree normally bearing flowers of only one sex -- produce pollen cones.

At the left, the yellowish, catkin-like items are pollen cones. The flat, fan-shaped leaves emerging in spring along with the pollen cones also are unusual, because the vast majority of gymnosperm species produce evergreen, needle- or scale-like leaves.

Ovules of Ginkgo biloba; image courtesy of Marcin Kolasiński of Poland, via Wikimedia Commons

At the right, on a female tree, you see pairs of ovules growing at the tips of stiff, straight stalks arising from twigs. To those of us accustomed to finding ovules inside ovaries in angiosperm flowers, and even in gymnosperm cones having ovules resting atop scales, seeing ovules simply being held out in the air is almost shocking. However, Ginkgoes arose before Nature came up with the idea of plant ovaries, and somehow they even missed out on cone scales. Gingkoes are primitive, true living fossils!

Normally, but not always, the weaker of the pair of ovules aborts, leaving only one ovule atop the stalk to mature into a plum-like seed, shown at the left. These seeds are so like plum fruits that at first it's hard to think of them as seeds, not fruits. However, morphologists assure us that the soft, fleshy part of what we see atop the stalks is modified seed coat. In a real fruit, such as a plum, the fleshy part is the mesocarp, derived from the wall of a flower's ripened ovary and gymnosperms, by definition, don't have ovaries surrounding their ovules. Those things are seeds with a fleshy outer part and a hard inner part, not fleshy fruits bearing hard seeds!

But, admittedly, holding a Ginkgo seed in your hand seems like holding a fruit, not a seed. You just have to believe the morphologists, and the definition of gymnosperm.

As seen at the right, Ginkgo leaves also display a primitive condition. Their veins create a pattern called open dichotomous branching. At first glance the veins look "parallel" to one another, but notice that along the veins' lengths they fork. Later-evolved flowering plants, the angiosperms, normally display the "closed vein system," while most gymnosperms, who arose before angiosperms, possess open vein systems.

A final primitive feature displayed by Ginkgoes deserves consideration: They tolerate air pollution. The first Ginkgo species arose during the Permian Period, before there were dinosaurs and flowering plants, and since then ginkgoes have survived three mass extinctions. Each of those mass extinctions involved drastic disruptions of the atmosphere, whatever their cause was. During the Permian Period, global atmospheric oxygen levels dropped to about 15%, lower than the current level of 21%. (University of Michigan web page).

With the current human-caused mass extinction underway, we can hope that more than the Ginkgo will survive, again. The Ginkgo is wind pollinated. A 2016 UN report warns that more than 40% of invertebrate pollinator species, particularly bees and butterflies, face extinction, and another 16% of vertebrate pollinators are also under threat. Wind pollination seems a good bet for the future. Also, it's thought that the first ginkgoes evolved with adaptions for surviving in frequently disturbed streamside environments. "Specializing in disturbed environments" also seems like a good bet for the future.

Many millions of years ago, the Ginkgo adapted certain simple, primitive strategies, which in the end may prove more sustainable than all other strategies arisen since then, even that of having organisms with human minds.