Rhododendron subgenus Tsutsusi

''Rhododendron'' section ''Tsutsusi'' (spelled ''Tsutsuji'' in some older texts) was a subgenus of the genus '' Rhododendron'', commonly referred to as the evergreen azaleas. In 2005 it was reduced to a section of subgenus ''Azaleastrum''. Containing 80 - 117 species, it includes both deciduous and evergreen types and is distributed in Japan, China and northeastern Asia. They are of high cultural importance to the Japanese. Among the species in this genus lie the largest flowering azaleas.

Description

Tsutsusi are characterised by the presence of terminal buds that contain both floral and vegetative shoots. Many also have flattened multicellular ferrugineous (rust coloured) hairs, which can cover the leaves and stems providing a coppery appearance, or pseudoverticillate leaves that are rhombic in shape. However some have hairs confined to the axils, or base of floral buds.

Taxonomy

The section has traditionally included two subsections, classified on the basis of their leaves, young twigs and corolla. Phylogenetic analysis has confirmed both the monophyly of the section and its subsections.

Subsections

*''Rhododendron'' subsect. '' Brachycalyx'' Sweet, type '' Rhododendron farrerae''. 15 species. - leaves deciduous, pseudoverticillate, rhombic, crowded at the shoot apex and monomorphic, hairs usually confined to axils, found mainly outside China.
*''Rhododendron'' subsect. ''Tsutsusi'' Sweet, type ''Rhododendron indicum''. 66 species. - leaves dimorphic, generally deciduous but some apical leaves over winter, young twigs with flattened multicellular hairs that are more widely distributed.

The results of molecular analyses reveal that morphological features such as flower colour, corolla size, or whether leaves are mono- or dimorphic, appear to not be very useful in sorting out the
phylogenetic relationships within section ''Tsutsusi''.

Etymology

''Tsutsusi'' comes from the Japanese word for Azalea, ''Tsutsuji'' ( つつじ or ツツジ). When Don (1834) described the subdivisions of ''Rhododendron'' he named one of his eight sections, ''Tsutsutsi'' (sic), which he explained was the Chinese name of the first species described (''R. indicum'', originally ''Azalea indica'' L.). The term was first used by Engelbert Kaempfer (who unlike Linnaeus preferred native names), in Japan and then incorporated into Michel Adanson's taxonomy (1763) as ''Tsutsusi'' Kaempf., a genus separate from ''Rhododendron'', in the family Vaccinia or ''Aireles'' (Family 22/58, later Ericaceae). Adanson gives genus ''Tsutsusi'' as synonymous with the earlier ''Azalea'' L. Subsequent authors such as Don (1834) and Candolle (1838) continued the use of the vernacular word ''Tsutsusi'' to describe a subdivision of the genus.

Distribution

Temperate and subtropical regions of China and Japan, but also found occasionally in Korea, Thailand, Burma, Laos and India.

Cultivation

The Tsutsusi are amongst the most popular of the cultivated azaleas, and were cultivated in China and Japan prior to their introduction to Europe, and have an important role in the horticultural industry. They are grown as landscape plants in appropriate climates, and also as potted plants and Bonsai.

References

Bibliography

Wilson EH, Rehder A. A MONOGRAPH OF AZALEAS RHODODENDRON SUBGENUS ANTHODENDRON. THE UNIVERSITY PRESS, CAMBRIDGE April 15 1921. PUBLICATIONS OF THE ARNOLD ARBORETUM, No. 9
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External links

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Flora of China

Tropicos
see als
Section Tsutsusi
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{{Taxonbar, from=Q21378817

Tsutsusi
Plant sections