Scientific Name

Synonyms

Radermachera borii C.E.C Fisch.

Radermachera tonkinensis Dop

Stereospermum sinicum Hance

Family

Bignoniaceae

Common Names

china doll tree, serpent tree, emerald tree.

Dwarf varieties of Radermachera sinica are often referred to by the common name of "Asian bell tree".

Origin

Cultivation

Radermachera sinica is used as an indoor house plant and is valued for its decorative foliage as it rarely flowers inside a building. (The dwarf form, Asian bell tree, is most commonly used.)

As an ornamental garden plant, the species requires rich, well drained soil in either full sun or part shade.

Naturalised Distribution

The only report of a naturalised distribution of this species comes from Hawaii where it seems to have become naturalised in the Waimea Botanical Garden.

Habitat

Habit

Radermachera sinica is normally an evergreen tree with attractive, glossy, green, divided leaves. It can reach heights of 10-30 m and produces clusters of bell or trumpet shaped white flowers followed by very long (about 85 cm), slender seed pods which are produced in spectacular clusters.

Dwarf forms of this species consistently only reach about 3 m and are sold under the common name of Asian bell tree.

Distinguishing Features

• a long-lived evergreen tree 10-30 m in height; dwarf varieties up to 3 m tall.
• the leaves are bright green, glossy, bipinnate or sometimes tripinnate (have a central "stem" with leaflets on either side and which may subdivide twice for a tripinnate leaf), 20-70 cm long and 15-25 cm broad; the individual leaflets are 4-7 cm long.
• its flowers are white (sometimes yellow) with five rounded and crinkly petals, trumpet-shaped, fragrant, produced in clusters at the ends of the branches and individual flowers are 6-8 cm long.
• the fruit resembles a long, snake-like, angular, slender bean (up to 85 cm long and 1 cm in diameter) which is produced in clusters at the ends of the branches.
• the fruits split to release the elliptical, winged seeds which are about 2 cm long by 5 mm wide (inclusive of the wing).

Stems and Leaves

Young branches are smooth and green, older branches become more or less grey and are at first slanted upwards but then become almost vertical; the trunk is more or less grey and in mature trees that reach a maximum height of 20-30 m, the trunk diameter can reach up to 1 m.

The leaves are dark green, glossy and bipinnate or sometimes tripinnate (the leaves go through two successive internal stem divisions). The central leaf stem (rhachis) may be up to 30 cm long with some sources suggesting much longer lengths up to 70 cm are possible. The leaflets are arranged in opposite pairs on either side of the central stem (or on the sub-stem if tripinnate) and there is always a single terminal leaflet. The leaflets are smooth, have a long tapered tip, are prominently veined, have entire margins without any serrations and are more or less oval in outline, 4-7 cm long and 2-3.5 cm in diameter.

Flowers and Fruit

The flowers are white (yellow in some varieties), aromatic (somewhat like a carnation), trumpet-shaped, and display five rounded, crinkly petals about 2.5 cm in length. The flowers are about 6-8 cm long and are displayed in open clusters at the ends of the branches.

The fruit is a long, bean-like, angular capsule, up to 85 cm long and 1 cm in diameter. The capsules are produced in large clusters at the ends of the branches and split when ripe to release the winged seeds. The seeds are oval and including their attached wing, about 2 cm long and 5 mm in diameter.

Reproduction and Dispersal

Reproduction is by seeds.

The seeds are wind dispersed or possibly carried by birds which are said to feed on the seed pods.

Environmental Impact

There are no records of environmental impacts caused by this species.

Legislation

No species of Radermachera Zoll. & Mor is a declared weed in any state of Australia as at January, 2015. Radermachera sinica is classed as an "Undesirable Species" by the Noosa Shire Council under Local Law 10 - Vegetation Management 2003.

Management

Control of Radermachera sinica (China doll, Asian bell tree) is similar to other tree species. If the specimens are at seedling stage or early sapling stage, removal can be done by hand or with gardening tools. Larger saplings may require lopping and/or application of a herbicide.  Large trees need to be felled and removed.  Follow-up procedures may be necessary to control any seedlings if the parent trees had produced seeds.

Notes

There are 17 accepted species of Radermachera Zoll. & Mor. and a list is given below. Of these, R. sinica is by far the most common species found in Australia.  The plant (or its varieties) is regularly offered for sale in nurseries and there is at least one specimen plant in the Royal Botanic Gardens, Melbourne, Victoria.

Radermachera boniana Dop

Radermachera coriacea Merr.

Radermachera eberhardtii Dop

Radermachera frondosa Chun & F.C.How

Radermachera gigantea (Blume) Miq.

Radermachera glandulosa (Blume) Miq.

Radermachera hainanensis Merr.

Radermachera inflata Steenis

Radermachera ignea (Kurz) Steenis

Radermachera microcalyx C.Y.Wu

Radermachera peninsularis Steenis

Radermachera pentandra Hemsl.

Radermachera pinnata (Blanco) Seem.

Radermachera ramiflora Steenis

Radermachera sinica (Hance) Hemsl.

Radermachera stellata Steenis

Radermachera xylocarpa (Roxb.) Roxb. ex K.Schum.

Radermachera yunnanensis C.Y.Wu