Hydrangea chungii Rehder — Fujian hydrangea

Introduction

Fujian hydrangea (Hydrangea chungii) is a small woody shrub of southeastern China and a distinctive member of Hydrangea subg. Dichroa sect. Chinenses. Typical plants are only about 0.3–0.7 m tall but bear proportionally large, elliptic to oblong-elliptic leaves commonly 12–20 cm long. Young branches, leaves, and inflorescences are conspicuously rough-villous, while the broad terminal inflorescences combine fertile flowers with enlarged marginal flowers bearing three or four rounded white sepals. The fertile flowers have blue-purple petals, ten subequal stamens, three or four styles, and an ovary less than half superior. The small seeds are wingless or only shortly winged and have the reticulate seed coat characteristic of this part of subg. Dichroa (Wei & Bartholomew 2001).

The species is centered on northwestern Fujian and adjacent eastern Jiangxi, where it grows in dense forest, thickets, and along mountain trails at approximately 200–800 m elevation. Rehder described H. chungii in 1931, and McClintock later reduced it to H. macrophylla ssp. chungii. Modern treatments again recognize it at species rank, and expanded plastome sampling by Yang et al. (2024) placed authentic Fujian material securely within the restricted sect. Chinenses.

Its history nevertheless illustrates the difficulty of defining species within the old H. chinensis complex. Flora of China recorded Bruce Bartholomew's opinion that the Jiangxi taxon H. caudatifolia W.T.Wang & M.X.Nie should be included within H. chungii, and present-day Plants of the World Online follows that synonymy. Tree TSAR provisionally agrees, but the decision remains based primarily on morphology rather than direct molecular comparison of the two type concepts.

Comparison with the H. caudatifolia morphotype

Character	Typical Hydrangea chungii	**Hydrangea caudatifolia**
Habit	Small shrub, ca. 0.3–0.7 m	Shrub, ca. 1 m
Young shoots	Densely, roughly villous	Densely yellowish pubescent
Leaves	Ca. 12–20 × 4.5–8.5 cm	Ca. 7–19.5 × 2.5–8.5 cm
Leaf apex	Acuminate	Strongly caudate-acuminate
Secondary veins	8–10 pairs	7–9 pairs
Enlarged marginal sepals	3–4	Usually 4, sometimes 3 or 5
Fertile petals	Blue-purple, ca. 2 mm in bud	Purple, reportedly larger
Capsule	Subglobose, ca. 2.5–3 mm diameter	Smaller, ca. 1.5–2 mm diameter
Classical center	Northwestern Fujian	Eastern Jiangxi
Current Tree TSAR status	Accepted species	Heterotypic synonym requiring future review

The differences are real enough that caudatifolia should not disappear from the biological discussion simply because it is synonymized. Its more strongly caudate leaves, geographical concentration in Jiangxi, and several quantitative floral and fruit differences indicate a recognizable historical morphotype. At present, however, those differences have not been paired with evidence of independent evolutionary structure. The most appropriate treatment is therefore to retain H. caudatifolia within H. chungii while identifying it explicitly as a target for future population-level sampling.

The molecular evidence presently available supports the broader placement of H. chungii more strongly than it resolves its internal limits. Yang et al. (2024) included Fujian material and recovered it within sect. Chinenses, helping establish that the species is not simply a derivative of the superficially similar H. macrophylla lineage. Nuclear sampling across Fujian and eastern Jiangxi would be needed to determine whether the caudatifolia populations represent geographic variation, an incipient lineage, or an overlooked species.

Horticultural and Agricultural Uses

Fujian hydrangea appears to be very uncommon in cultivation. Its compact stature, unusually large leaves relative to plant height, conspicuous rough indumentum, and broad lacecap inflorescences suggest considerable interest for specialist collections, particularly those attempting to represent the evolutionary diversity of wild Hydrangea. Unlike many familiar ornamental hydrangeas, it is not known to have generated an important cultivar tradition or breeding history.

Its natural occurrence in moist forest and thicket habitats at relatively low to middle elevations suggests that living collections should emphasize protection from excessive drying and exposure rather than treating it simply as a diminutive form of bigleaf hydrangea. There is presently too little documented horticultural experience with authenticated material to justify more specific cultivation claims.

No agricultural, medicinal, or other major utilitarian use is documented in the sources reviewed.

Conservation Concerns

No formal global IUCN Red List assessment was located for Hydrangea chungii. Its documented native range is comparatively restricted, concentrated in northwestern Fujian and adjacent eastern Jiangxi.

The species has at least some regional conservation recognition: H. chungii appears on a 2024 Fujian provincial list of protected wild plants. This does not by itself establish the magnitude of population decline or extinction risk, but it reinforces the value of documenting wild populations and maintaining accurately identified ex situ material.

Taxonomic resolution also matters to conservation. If the Jiangxi caudatifolia element ultimately proves evolutionarily distinct, its range would be narrower than a broad H. chungii map implies. Voucher-linked population sampling across both Fujian and Jiangxi should therefore accompany any future conservation assessment.

Additional Information

Plants of the World Online — Hydrangea chungii (opens in a new tab): Current accepted name, distribution, and synonymy, including H. caudatifolia.

Flora of China — Hydrangea chungii (opens in a new tab): Detailed morphology, habitat, phenology, and Chinese distribution.

References and Further Reading

McClintock E (1957) A monograph of the genus Hydrangea. Proceedings of the California Academy of Sciences, Fourth Series 29(5): 147–256. https://www.biodiversitylibrary.org/part/51707 (opens in a new tab) https://doi.org/10.5281/zenodo.15905786 (opens in a new tab)

Rehder A (1931) New species, varieties and combinations from the herbarium and the collections of the Arnold Arboretum. Journal of the Arnold Arboretum 12(1): 59–78. https://doi.org/10.5962/p.324565 (opens in a new tab)

Wei Z, Bartholomew B (2001) Hydrangea. In: Wu ZY, Raven PH (eds.) Flora of China, vol. 8. Science Press, Beijing & Missouri Botanical Garden Press, St. Louis, pp. 411–422. https://www.iplant.cn/foc/pdf/Hydrangea.pdf (opens in a new tab)

Wei ZF (1994) A revision of the genus Hydrangea in China. Guihaia 14(2): 101–121. https://www.guihaia-journal.com/gxzwen/ch/reader/create_pdf.aspx?falg=1&file_no=199402002&quarter_id=2&year_id=1994 (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)