Family : Bignoniaceae
Text © Pietro Puccio
English translation by Mario Beltramini
The species is native to Assam, Bhutan, China (Guangdong, Guangxi, Guizhou and Yunnan), Japan (Ryukyu Islands), Myanmar, Peninsular Malaysia, Taiwan, Vietnam and Western Bengal where it grows in the forests up to about 800 m of altitude.
The genus is dedicated to the Dutch botanist Jacob Cornelis Matthieu Radermacher (1741-1783); the name of the species is the Latin adjective “sinicus, a, um” = of China, with reference to one of its origin places.
Common names: China doll, emerald tree, serpent tree (English); cai dou shu (Chinese); sendan kisasage (Japanese).
The Radermachera sinica (Hance) Hemsl. (1905) is an erect evergreen tree, 10-30 m tall and trunk, of up to about 80 cm of diameter, with greyish to pale brown wrinkled bark.
The leaves are opposite, bi-tri-imparipinnate, 20-70 cm long and 18-25 cm broad, with ovate-elliptic leaflets with usually entire margin, or irregularly and slightly crenate, and caudate-acuminate apex, 4-8 cm long and 2-3 cm broad, coriaceous, of intense green colour and glossy above.
Terminal panicle inflorescences or axillar at the apices of the branches, erect, 25-35 cm long, bearing bisexual white or pale yellow flowers, fragrant by night, of 6-8 cm of diameter. Campanulate calyx, 2-3,5 cm long with 5 triangular lobes having pointed apex, 0,4-0,6 cm long, of pale yellowish green colour. Corolla with imbutiform tube, 7-11 cm long, and 5 irregular curved and wavy lobes, 2-4 cm long and about 2 cm broad, and 4 didynamous stamens (two longer and two shorter).
The fruit is a cylindrical streaked, curved capsule, 30-70 cm long and about 1 cm broad, containing several ellipsoid winged seeds, 2-3 cm long and 0,5-1 cm broad, wing included. It reproduces by seed, placed superficially in draining loam rich of organic substance, maintained humid but without stagnations, at the temperature of 26-28 °C, with germination times of 2-4 weeks; it propagates also by cutting in summer.
Species of easy cultivation and fast growth with particularly ornamental foliage and the big flowers, cultivable in the tropical, subtropical and warm temperate climate regions, in full sun or partial shade, in a location protected from the strong winds; it can be utilized as isolated specimen, in group, for border screens and as road tree.
It requires fertile draining soils, maintained moderately humid, from slightly acidic to neutral. Due to the luxuriant foliage it is vastly utilized in pot for the decoration of particularly luminous inner spaces, but not in direct sun, with lowest night temperatures not under the 14 °C. The loam must be draining, aerated, rich of organic substance and the waterings regular, but moderate, during the growth period, then spaced in winter, but without ever allowing the substratum to dry up completely. Both the excess and the lack of water may cause the leaves fall, as well as the air currents, the displacements and the sharp temperature changes, furthermore, does not like the environments with polluted air. Though enduring the dry air of the dwellings, it takes advantage from regular nebulizations to be done with non calcareous water, to avoid unaesthetic spots on the leaves, at ambient temperature.
The fertilizations are to be done in spring-summer with hydrosoluble products, with microelements, suitable for green plants. Of fast growth also when in pot, it is to be periodically pruned, in spring-summer, to maintain compact its posture. In closed environments it is easily subject to attacks of parasites, such as mites, aphids and mealybugs, it is therefore to be kept under control in order to take prompt action with specific products.
Synonyms: Stereospermum sinicum Hance (1882); Radermachera tonkinensis Dop (1926); Radermachera borii C.E.C Fisch. (1940).
The photographic file of Giuseppe Mazza