Rhododendron sect. Tsutsusi

Rhododendron section Tsutsusi (spelled Tsutsuji in some older texts) was a subgenus of the genus Rhododendron, commonly referred to as the evergreen azaleas.[3][4][5] In 2005 it was reduced to a section of subgenus Azaleastrum.[6] 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.

Rhododendron sect. Tsutsusi
Rhododendron indicum
Scientific classification
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Eudicots
Clade: Asterids
Order: Ericales
Family: Ericaceae
Genus: Rhododendron
Subgenus: Rhododendron subg. Azaleastrum
Section: Rhododendron sect. Tsutsusi
(Sweet) Pojarkova[1][2]
Type species
Rhododendron indicum
(L.) Sweet
Subsections

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.[5]

Taxonomy

The section has traditionally included two subsections,[5][7] classified on the basis of their leaves, young twigs and corolla. Phylogenetic analysis has confirmed both the monophyly of the section and its subsections.[4]

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.[5]

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.[5]

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.).[8] The term was first used by Engelbert Kaempfer (who unlike Linnaeus preferred native names),[9] in Japan and then incorporated into Michel Adanson's taxonomy (1763)[10] 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.[11] Subsequent authors such as Don (1834) and Candolle (1838)[12] 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.[5]

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.[5]

References
  1. Sweet R. The British Flower Garden. Fl. Gard., ser. 2, 2: t. 117. 1831
  2. Pojarkova AI, in Schischkin & Bobrov, Flora URSS. 18: 55. 1952.
  3. Chamberlain, DF; Hyam R; Argent G; Fairweather G; Walter KS (1996). The genus Rhododendron: its classification and synonymy. Royal Botanic gardens Edinburgh. ISBN 1-872291-66-X. Archived from the original on July 14, 2014. Retrieved July 3, 2014.
  4. Powell, Kron; Ann, E.; Kathleen, A. "Molecular systematics of Rhododendron subgenus Tsutsusi (Rhodoreae, Ericoideae, Ericaceae)". Botany. 2004: 147.
  5. Kron, K. A.; Powell, E. A. (2009). "Molecular Systematics of Rhododendron Subgenus Tsutsusi (Rhodoreae, Ericoideae, Ericaceae)". Edinburgh Journal of Botany. 66: 81. doi:10.1017/S0960428609005071.
  6. Goetsch, Loretta A.; Eckert, Andrew J.; Hall, Benjamin D. (July–September 2005). "The molecular systematics of Rhododendron (Ericaceae): a phylogeny based upon RPB2 gene sequences". Systematic Botany. 30 (3): 616–626. doi:10.1600/0363644054782170. S2CID 51949019.
  7. Loretta Goetsch, Andrew Eckert and Benjamin Hall. Classification of genus Rhododendron. 2005 Annual ARS Convention
  8. Don G. General History of Dichlamydious Plants. 1834 iii 843
  9. Amoenitatum exoticarum politico-physico-medicarum fasciculi v, quibus continentur variae relationes, observationes & descriptiones rerum Persicarum & ulterioris Asiae, multâ attentione, in peregrinationibus per universum Orientum, collecta, ab auctore Engelberto Kaempfero: Tsutsusi. Lemgoviae, Typis & impensis H.W. Meyeri, 1712. Page 845ff. Archived 2007-12-09 at the Wayback Machine
  10. Adanson, Michel (1763). Familles des plantes. v. 1-2. Paris: Vincent. p. 164. Retrieved 9 February 2014.
  11. Beatrice Bodart-Bailey, Derek Massarella. The Furthest Goal: Engelbert Kaempfer's Encounter with Tokugawa Japan. Routledge, 2012. Page 92. ISBN 1136637834
  12. A. P. de Candolle; et al. (1838). "Tsutsusi". Prodromus systemati naturalis regni vegetabilis sive enumeratio contracta ordinum, generum specierumque plantarum huc usque cognitarum, juxta methodi naturalis normas digesta. Part VII. Paris: Treuttel et Würtz. p. 726.

Bibliography
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