It’s a happy person that doesn’t have cancer. And it’s a Happy Tree that might provide one of the cures for cancers. Camtothecin was discovered by western medicine in the 1950s, when it was extracted from what we call the Happy Tree, from the Chinese name Xi Shu. Botanically it’s known as Camtotheca acuminata, one of two species in the genus Camtotheca – a name that translates as ‘curved sheath’, a possible reference to the miniature banana-like fruits.
The tree is native to southern China and Tibet, but nowadays at least uncommon in nature. Seed from one of the remaining 4000 trees was collected from Yunnan Province about 20 years ago by our Curator of Chinese Collections, Terry Smyth.
According to a 2011 report by the Rural Industries Research and Development Corporation (RIRDC), demand for this chemical worldwide is estimated to require at least 100 million trees. So we need to grow more than 99,996,000. We have nine growing in Melbourne Gardens, all sourced from the seed collected by Terry.
The tree is described in the report as ‘easy to grow in Australia‘ but does need a good source of moisture. One of our Senior Curators, and water guru, Peter Symes thinks the tree I’ve photographed here has done so well because of its roots are sourcing moisture from the lake. Colleague Steven Liu, who grew up in China, says it seems to grow better here than in its home country.
As you can see in the top photograph, this particular tree (the tall one) was planted next to the William Tell Rest House. This structure is a miniature version of a similarly named chapel in Lucerne, Switzerland. I don’t know of any particular resonance with the Melbourne Gardens but happily, according to the 15th century legend, William Tell’s arrow splits the apple on top of a nobleman’s son’s head and so lived to have his tale told.
These are the first pictures of the first flowering of our Happy Tree. The flowers are in a head, like a pom pom, with the male parts (stamens) prominent. If you look closely you can some tiny lime-green blobs on the spongy surface of the female centre of each flower; this is where the pollen from another flower needs to land. The flower without stamens in the top picture is older and, if fertilised, on its way to producing a cluster of scimitar-shaped fruits. As Terry says, ‘the globular flowers are interesting but not particularly beautiful‘ (they are certainly high in the tree and difficult to photograph).
But chemicals in its stem and bark are worth celebrating. While you hear plenty of reports of cancer-curing plants, camptothecin has been described as ‘the most promising anti-cancer drug … ever …found’. It is one a range of drugs that inhibits chemical reactions inside the body leading to reduced tumor growth.
Its complicated chemical structure makes it hard to synthesise in the laboratory, so the main source of the drug is still the Happy Tree (although there are side effects from this drug which artificial preparations may be able to minimise). The market for camptothecin in 2004 was worth a billion US dollars.
The 2011 study concludes that the tree is fast growing and suited to warm, humid regions of Australia such as coastal Queensland. So while there might not be potential for a Victorian industry, we can grow and marvel at this tree in our gardens if we plant wisely.
Planting wisely is how we intend to adapt to climate change at the Melbourne Gardens. Sometimes it means planting new kinds of plants, but it also means thinking about where and how we plant trees, taking best advantage of nooks and crannies such as this idyllic lakeside setting.
Like the Handkerchief Tree, this odd plant used to be in the family Nyssaceae but is now included in the dogwood family, Cornaceae. In leaf it’s not unlike Cornus I guess. In a 2007 piece written for Dave’s Garden Jeremy Lucas compares the leaves to those of an avocado, but with ‘heavier, pleated veining‘. That seems about right.
Jeremy Lucas tried to track down why it was called Xi Shu (Happy Tree) in China but didn’t get a definitive answer. Perhaps it is due to its tall, handsome stature and bright green leaves. Alternatively, as I thought when I started writing this and as a Chinese correspondent suggested to Lucas, the happiness may be related to curing disease, given it has long been a medicinal tree in China.
And if that doesn’t satisfy you, track down the apocryphal story on ChinaHorticulture.net. I don’t get it but the legend starts with a thing called Desperate Grass in the Garden of Eden, and ends with singing trees on a desert island. God plays a major role, and Adam and Eve bit parts, but the plants really star. In the end, the singing trees are given the name Happy Trees because wind blowing through them makes a similar (pleasing) sound to wind through the exiled Desperate Grass. Everyone, except perhaps Adam and Eve, are happy.