Hydrangea taiwaniana
Taiwan sprawling hydrangea
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Introduction
Taiwan sprawling hydrangea is one of the least satisfactorily understood accepted species of Hydrangea. Described from Taiwan in 1977, it continues to be recognized as a distinct species by Taiwanese botanical resources and World Flora Online, which records it as native to Taiwan. Yet the modern descriptive record available online is strikingly incomplete: the Plants of Taiwan account confirms the name and original publication but currently leaves its morphology, specimen documentation, photographs, and distributional treatment under development. 台灣植物資訊整合查詢系統 Plants of TAIWAN (opens in a new tab)
Tree TSAR provisionally places H. taiwaniana in Section Cornidia, with closest attention directed toward the widespread Taiwanese and Philippine H. integrifolia. That placement should be understood as a working hypothesis rather than a demonstrated phylogenetic result. The densely sampled Cornidia study of Granados Mendoza et al. (2021) included H. integrifolia as the section’s Asian representative but did not sample H. taiwaniana. Likewise, the broader phylogenomic framework of Yang et al. (2024) substantially strengthened the modern infrageneric classification of Hydrangea but did not resolve the taiwaniana–integrifolia problem directly.
This evidentiary gap matters because Cornidia has a distinctive suite of traits—persistent woody root-climbing growth, involucral inflorescence buds, and, in most species, functional dioecy—but none of these should simply be assigned to H. taiwaniana by association. Even the hermaphroditic reproductive system documented in H. integrifolia cannot safely be transferred to it. Until the protologue, type material, reliably identified living plants, and new molecular samples are brought together, the architecture and reproductive biology of H. taiwaniana should remain explicitly documented as unresolved rather than reconstructed from its provisional sectional placement.
The central taxonomic question is consequently straightforward but important: does H. taiwaniana represent a genuinely distinct Taiwanese lineage closely allied to H. integrifolia, or does it fall within the morphological and genetic variation of H. integrifolia itself? Tree TSAR retains it at species rank while that question remains unanswered. A type-anchored comparison followed by sampling of Taiwanese H. integrifolia populations and authenticated H. taiwaniana would provide a decisive test.
Horticultural and Agricultural Uses
No species-specific horticultural history can presently be assigned to H. taiwaniana with confidence. This is particularly important because H. integrifolia is cultivated internationally, including from Taiwanese collections, and poorly documented plants could readily circulate under one name while belonging to the other. Cultivation reports should therefore be accepted as evidence for H. taiwaniana only when the material can be traced to a reliably identified wild provenance.
This uncertainty also makes authenticated living material unusually valuable. Carefully documented accessions could provide the architectural, phenological, floral, and reproductive observations that herbarium material alone may not settle, while simultaneously creating an ex situ resource for genomic comparison with H. integrifolia.
Conservation Concerns
No formal IUCN assessment was located for H. taiwaniana, and currently accessible authoritative records do not provide enough detailed occurrence or population information for a defensible independent conservation assessment. World Flora Online recognizes a native Taiwanese distribution, while the Taiwanese Plants of Taiwan account confirms the taxon but has not yet populated its distributional or specimen sections (World Flora Online Consortium 2026).
Taxonomic uncertainty is itself the immediate conservation issue. If H. taiwaniana is genuinely distinct and localized, its populations could be much more restricted than records filed under a broader H. integrifolia concept would suggest. Conversely, if the two prove conspecific, Taiwanese populations may still contain important geographic structure. Type study, field relocation, voucher-backed observations, and genomic sampling should therefore precede confident statements about rarity or threat.
Additional Information
- Plants of Taiwan — Hydrangea taiwaniana (opens in a new tab): authoritative Taiwanese nomenclatural record, including the 1977 publication citation; descriptive and distributional fields are presently incomplete.
- World Flora Online — Hydrangea taiwaniana (opens in a new tab): recognizes the species and records Taiwan as its native distribution.
References and Further Reading
Granados Mendoza C, Martínez Salas EM, Goetghebeur P, Wanke S, Samain M-S (2021) Molecular phylogeny, character evolution, and biogeography of Hydrangea section Cornidia, Hydrangeaceae. Frontiers in Plant Science 12: 661522. https://doi.org/10.3389/fpls.2021.661522 (opens in a new tab)
Lu FY (1977) 臺灣雙子葉植物新見（三）. Quarterly Journal of Chinese Forestry 10(3): 85–102. https://nametool.taicol.tw/zh-tw/references/10092/usages (opens in a new tab)
World Flora Online Consortium (2026) Hydrangea taiwaniana . World Flora Online. https://www.worldfloraonline.org/taxon/wfo-0000726263 (opens in a new tab)
Yang X, Xue T, Gao T, Liang Y, Smets EF, Gadagkar SR, Yu S (2024) An updated infrageneric classification based on phylogenomics and character evolution in Hydrangea (Hydrangeaceae). Taxon 73(2): 503–518. https://doi.org/10.1002/tax.13158 (opens in a new tab)