Davidia involucrata is the only member of its genus, but there are two varieties differing slightly in their leaves, D. involucrata var. involucrata, which has the leaves thinly pubescent on the underside, and D. involucrata var. vilmoriniana, with glabrous leaves. Some botanists treat them as distinct species, with good reason, as the two taxa have differing chromosome numbers so are unable to produce fertile hybrid offspring.
Description
It is a moderately fast-growing tree, growing to in height, with alternate cordate leaves resembling those of a linden in appearance, except that they are symmetrical, and lacking the lop-sided base typical of linden leaves; the leaves are mostly 10–20 cm long and 7–15 cm wide and are ovate to heart-shaped. Davidia involucrata is best known for its inflorescence that features white bracts surrounding a purplish-red flower head. The Latin specific epithetinvolucrata means "with a ring of bracts surrounding several flowers". These form a tight cluster about 1–2 cm across, each flower head with a pair of large, pure white bracts at the base performing the function of petals. The inflorescences hang in long rows beneath the level branches and are at their best in late May. On a breezy day, the bracts flutter in the wind like white doves or pinched handkerchiefs, hence the English names for this tree. The fruit is a very hard nut about 3 cm long surrounded by a green husk about 4 cm long by 3 cm wide, hanging on a 10 cm stalk. The nut contains 3–6 seeds.
History
The genus Davidia is named for Father Armand David, a French Vincentian missionary and keen naturalist who lived in China. David first described the tree in 1869 as a single tree found at over altitude, and sent dried specimens to Paris; in 1871, Henri Baillon described it as a new genus and species. British plant hunterAugustine Henry again found a single tree, this time in the Yangtse Ichang gorges and sent the first specimen to Kew Gardens. Plant collectorErnest Henry Wilson was employed by Sir Harry Veitch to find Henry's tree but arrived to find that it had been felled for building purposes; however, he later found a grove of the trees overhanging a sheer drop. Returning to Britain, Wilson’s boat was wrecked, but he managed to save his Davidia specimens.
The species was introduced from China to Europe and North America in 1904, and is a popular ornamental tree in parks and larger gardens. Most trees in cultivation are var. vilmoriniana, which has proved much better able to adapt to the climatic conditions in the west. This tree and the cultivated varietyD. involucrata var. vilmoriniana have gained the Royal Horticultural Society's Award of Garden Merit.
