The last natural home of the ginkgo, perhaps

The last time I posted here about ginkgo it was after an unfulfilled quest to find one of its remaining natural homes in China, on Jinfo Mountain near Chongqing. This time, I'm further south, in the Tianmu Mountain a few hours from Shanghai. And this time, I found my tree.

But is this a Ginkgo biloba tree grown from seed dispersed and planted without the intervention of humans? That I can't be sure, and there is still much debate on this topic. Helpfully, I visited with one of scientists who sequenced ginkgo from across China searching for clues as to the location of remnant populations.

Chen Chuan is now Section Chief of Research and Popular Science at the Hangzhou Botanical Garden, said to be the first botanic garden constructed in 'New China' (since the revolution) and not far from Tianmu Mountain.

Chuan explains (here, and on radio a few weeks back) that while the population here has less diversity than for example the one at Jinfo Mountain, it has many attributes of a 'natural population'. There are definitely planted trees near a temple at the base of the mountains but up here we find ancient colonial clumps among a diverse range of other natural species. (To complicate things a little though, there are a number of definitely planted mature trees along some parts of the path to the ginkgo grove.) 

I also had with me, leading our tour, the Director of Hangzhou Botanical Garden, Jinliang Yu. He explained that the Tianmu Mountain biosphere reserve supports 2,351 plant species, including many not found elsewhere in the world and many that are rare and threatened. For example, a rare beech tree relative called Ostrya rehderiana, with only five individuals left in nature. 

Within this diverse flora are many old and large trees, including giant conifers called Cryptomeria japonica var. sinensis. The ginkgo is a little like a conifer, but not quite. In fact its on an entirely separate branch in the tree of life from conifers, cycads and flowering plants. It has motile sperm rather than pollen and a seed inside a hard coat within a fleshy fruit (which stinks like vomit).

The most famous ginkgo on the mountain is this one, called the ‘Family of Five Generations’. It is actually a collection of ginkgo trees, or suckers, that have resprouted over millennia from an ancestor (the ‘father tree’) over 12,000 years ago. There are suckering plants elsewhere in the world, including Australia, that are over 12,000 years old but the importance of this specimen is the support it gives to this population being one of the few places on Earth where the ginkgo grows naturally. 

I visited on a misty day and the ginkgo were just bursting into leaf. Beautiful but also opaque, like the story of the natural ginkgo. Still, there is more to life and the ginkgo than whether you are planted by man/woman or by a hungry civet.

I was reminded by Chuan of the various medicinal uses of the ginkko, and advised to eat a seed or two if I had the chance. But no more than seven. They contain a poison that starts to outway the health benefits when you hit the eighth seed. So it was with great care I navigated this plate of prawns and ginkgo seeds at a banquet that night. I decided to stick with three.

At the end of my chat with Chuan she asked did I know if the tree in front of us was male or female (ginkgo trees have either male or female flowers, not both)? I looked around and said all I could see was young leaves and no flowers or fruits, so no I couldn't. 

Look at the branches she said. They are drooping downwards, so this is a female tree. Over time the weight of the fruit bends the branches on the female plant while those of the male continue to head skyward. I didn't know that and although it doesn't help with that critical decision when young (most people want to plant male plants, without the vomit-smelling fruit) it is a fun fact.

Postscript: a few more fossils from Beijing Botanical Garden (South). This time a couple of close relatives of the ginkgo, in the fossil genus Ginkgoites. Note the leaves are not 2-lobed, as in extant Ginkgo biloba.