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Hydrangea hydrangeoides var. taquetii (H.Lév.) J.M.H.Shaw

Jeju hydrangea vine

Synonyms
  • Hydrangea taquetii H.Lév.
  • Schizophragma hydrangeoides var. taquetii (H.Lév.) J.M.H.Shaw
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Introduction

The Jeju hydrangea vine, Hydrangea hydrangeoides var. taquetii, is the distinctive Jeju Island representative of the Japanese hydrangea-vine complex. Kew currently accepts it as a variety endemic to Jeju, and Tree TSAR agrees that formal varietal rank is justified provisionally by the combination of island geography, recognizable morphology, and limited molecular evidence suggesting that the Korean island populations are not homogeneous.

The taxon's history extends considerably further back than the other named island varieties. Hector Léveillé described the Jeju plant as the species Hydrangea taquetii in 1910. Julian Shaw later reduced it to Schizophragma hydrangeoides var. taquetii in 2012 and subsequently transferred that combination back into Hydrangea in 2021. Kew accordingly recognizes H. taquetii and the Schizophragma varietal combination as homotypic synonyms of the accepted variety.

The Jeju plants are particularly notable for a distinct dwarf juvenile phase. Mature climbing shoots develop ovate leaves reported at approximately 12.5–16 × 9–11 cm, while leaves subtending the inflorescences are more ovate-lanceolate and possess few or no marginal teeth. Shaw regarded the combination of juvenile development and mature foliage as sufficient to distinguish the island population (Shaw 2012; Sutton 2025).

Variation within Jeju is nevertheless substantial. The variety should not be imagined as a perfectly uniform island clone, and Korean treatments have not adopted it as consistently as Western horticultural and taxonomic sources. Joung et al. (2010) used RAPD and rbcL markers while investigating wild Korean Hydrangeaceae and demonstrated the utility of molecular data in separating morphologically confusing climbing hydrangeas. Sutton's synthesis of that study further reports that Ulleungdo H. hydrangeoides grouped with Japanese material rather than with the Jeju population. This result is compatible with recognizing the Jeju population as differentiated, but the marker set was not designed as a modern population-genomic test of varietal boundaries.

Tree TSAR therefore retains var. taquetii because differentiation is supported along at least two meaningful axes: morphology and strong island geography, with suggestive molecular structure providing additional context. The evidence does not presently justify species or subspecies rank. Dense nuclear sampling across Jeju and the Japanese main-island populations could either strengthen the case for deeper independence or demonstrate that the current variety captures only one end of continuous regional variation.

Horticultural and Agricultural Uses

Jeju material is well represented in specialist cultivation through documented wild collections. Crûg Farm accessions BSWJ 1160 and BSWJ 8771 belong to this population. The cultivar ‘Cheju's Early’ was selected from BSWJ 1160 and is notable for exceptionally early flowering, sometimes beginning in April or May under North Welsh conditions (Shaw 2012; Sutton 2025).

This horticultural presence makes retention of the variety particularly useful. Plants collected from Jeju can be discussed within a biologically meaningful geographical framework rather than being collapsed into undifferentiated Japanese H. hydrangeoides. At the same time, named cultivars such as ‘Cheju's Early’ remain cultivars within the variety, not synonyms for it.

The dwarf juvenile growth phase may also have horticultural consequences, affecting how young plants establish and how quickly they begin vertical climbing. Comparisons among authenticated Jeju, Ulleungdo, Yakushima, and Japanese-mainland material could therefore provide useful developmental as well as taxonomic information.

Conservation Concerns

No formal global conservation assessment was located for var. taquetii. Its restriction to Jeju makes it inherently more geographically concentrated than H. hydrangeoides as a whole, but the evidence reviewed here does not establish that it is rare, declining, or immediately threatened.

The principal conservation issue is maintenance of population-level diversity across Jeju. Because significant morphological variation has already been reported within the island population, conserving a single horticultural accession would not adequately represent the variety. Multiple wild populations should be documented and, where appropriate, incorporated into well-provenanced ex situ collections.

Population genomics would be especially valuable because taxonomic recognition and conservation prioritization are intertwined. Strong island-wide genetic coherence would reinforce the present variety treatment, whereas extensive overlap with neighboring Japanese populations would weaken the case for formal rank while leaving the Jeju population biogeographically important.

Additional Information

References and Further Reading

Joung YH, Suh JK, Lee NS, Eum SM, Choi I-Y, Roh MS (2010) Identification of Hydrangeaceae accessions of wild origin from Jeju, Korea, using molecular markers. Plant Genetic Resources 8(3): 235–241. https://doi.org/10.1017/S1479262110000286

Royal Botanic Gardens, Kew (2026) Hydrangea hydrangeoides var. taquetii (H.Lév.) J.M.H.Shaw. Plants of the World Online. https://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:77296094-1

Shaw JMH (2012) Climbing hydrangeas and their relatives. The Plantsman, New Series 11(4): 226–231. https://www.rhs.org.uk/about-us/pdfs/publications/the-plant-review/general-pdfs/index-for-2012.pdf

Sutton J (2025) Hydrangea hydrangeoides. Trees and Shrubs Online. International Dendrology Society. https://www.treesandshrubsonline.org/articles/hydrangea/hydrangea-hydrangeoides/