Tuesday, 29 March 2016

Handkerchief tree in full blow


Appropriately, as Christians and others celebrate Easter, today my talking plant celebrates Père (Father) Armand David, a missionary who himself became converted - to become a naturalist - during his time in China. He was the first European to 'discover' the Giant Panda and has numerous animals and plants named after him. The plant most often associated with his name is the Dove Tree or Handkerchief Tree, Davidia involucrata.

Jane Kilpatrick tells his story, and that of other European missionaries who botanised in China, in her recent (2014) book Fathers of Botany. David was born in the south-west of France in 1826 and Kilpatrick says he credits his Basque upbringing for his stamina.

The Dove Tree was found by David in 1869, in the Baozing County of Sichuan Province in central China, where he also found the Giant Panda. Both live in mountain forests, the Dove Tree between 1100 and 2600 meters above sea level.


The flowers are small and clustered together, but like a few other plants I've mentioned, they are associated with large showy 'bracts'. There are two bracts in this case, each resembling a handkerchief or something more romantic. Irish botanist Augustine Henry saw a single tree in flower in 1888 and says it was 'one of the strangest sights… a solitary tree of davidia in full blow…waving its innumerable ghost handkerchiefs'.

A decade later, noted English plant collector, E.H. Wilson, described the bracts blowing the breeze as resembling 'huge butterflies or small doves hovering among the trees'. In fact it's said (Seamus O'Brien, In the Footsteps of Augustine Henry and his Chinese plant collectors) that to see this plant in nature was the sole reason Wilson made his first visit to China.

The first illustrations of the flowers were from pressed, dried specimens, and the bracts were shown sticking upwards. In fact, of course, they flutter downwards like someone waving a white handkerchief.

You'd think these bracts have something to do with attracting pollinators to the inconspicuous flowers, although perhaps not biped mammals. The Arnold Arboretum in the USA has helpfully done the research, concluding that the bracts are part umbrella (shielding the flowers to keep pollen dry) and partly sex appeal (attracting insect pollinators). They even help support the tree when young, producing sugars from sunlight (photosynthesis), before they turn from green to white.



This is an odd plant, often classified with the Tupelo, Nyssa sylvatica, and Happy Tree (more on the latter in two weeks time...), in the family Nyssaceae. (The Tupelo has beautiful autumn colour, always attracting attention in April in the Melbourne Gardens.) In the past the Dove Tree has been also placed in its own family, the Davidiaceae, but the latest molecular classifications include the family Nyssaceae within an expanded Cornaceae (some species of which have four large petal-like bracts around the flowers, not dissimilar and often as striking as the Dove Tree flowers).

Henry (and no I don't know why all the surnames can double as first names) had actually found a new variety of the Dove or Hankerchief Tree, later named vilmoriniana. It had smooth, hairless leaves (apart from a few hairs on the under surface of the veins) compared with the downy under surface of the leaves collected by David. This variety is now the most common in cultivation, particularly in cooler regions.


While we don't distinguish on our census what variety we have in Melbourne Gardens, the leaves of the one specimen I could find don't have a hairy under surface so I'm presuming they belong to variety vilmoriniana. And if I enlarge the pictures I took in the garden of Tieve Tara, at Mount Macedon, in October 2014 (adorning this post), again I don't see any overt hairiness.

That's settled then. We can now just enjoy the flowers in full blow.


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