Earlier this week, I walked past this Davidia involucrata tree in UBC Botanical Garden and was surprised to see it waving hundreds of white “handkerchiefs” at me. I had never seen a plant with this characteristic before, so of course I had to stop and photograph the unusual inflorescences.
Today’s photo offers only a glimmer of why Davidia involucrata is commonly called dove tree or handkerchief tree. At the slightest breeze, the white bracts begin to twist and flutter in a bizarre and beautiful dance of surrender. They are impossible to ignore–and with all of that motion, rather difficult to photograph! The flowers are dark purple, small and both petal-less and nectar-less, and collected into globose heads that are dwarfed by two large bracts that change from green to white at anthesis (full bloom). One of the bracts is about twice the size of the other; I suspect this asymmetry is what causes the bracts to flutter so attractively. These bracts attract bees and other pollinators, but it is their role as rain shelters that I find the most fascinating. In an article (PDF) published in Arnoldia, Sun and Huang point out that Davidia involucrata blooms during the rainy season (in its native range of western China), and that anthesis occurs over a relatively long period of time, likely because of low pollinator visitation rates. These factors result in the pollen being particularly vulnerable to being washed away. Handkerchief tree solves this problem by growing a pair of little white umbrellas over each of the inflorescences.
Handkerchief tree is a very rare species, and most botanists agree that it is the only member of its genus (see the previous BPotD post on Davidia involucrata). It is considered a relic of the (formerly used) Tertiary period. The species is endangered in China, where its range is being reduced by human activity. Efforts are being made to propagate Davidia involucrata, in hopes of establishing it in natural reserves, gardens, and farms in China and around the world.