Hydrangea villosa Rehder — Velvetleaf hydrangea

Introduction

Velvetleaf hydrangea (Hydrangea villosa Rehder) is a deciduous woody shrub of central China and one of the species historically submerged within the broad Hydrangea aspera complex. Rehder described it from Ernest Henry Wilson collections, but McClintock and later Flora of China treatments reduced it into H. aspera. Current Plants of the World Online still treats the name as a synonym of that species.

Modern molecular evidence supports the opposite conclusion. Multilocus coalescent delimitation, RADseq species delimitation, and reciprocal monophyly all recover H. villosa as an independently evolving lineage. Its precise position within the hairy core remains difficult to resolve, but uncertainty about which species is its closest relative does not undermine the coherence of H. villosa itself.

Character	H. aspera	H. aspera ssp. robusta	H. kawakamii	H. strigosa	H. villosa
Core geography	Mainland Asian complex	E Himalaya–S China–Indochina	Taiwan	Hubei type lineage	Central China
Main hair character	Variable	Variable, often dense	Long erect hairs	Short stiff appressed hairs	Long erect/villous hairs; brownish on major veins
Leaf texture beneath	Variable	Often densely hairy	Hairy with subtle papillae	Rough, appressed-strigose	Coarsely velvety
Cytology	2n = 34/36 reported	2n = 34 reported	2n = 36	2n = 34	2n = 34
Molecular result	Complex/permeable	Subspecies	Distinct	Hubei lineage distinct	Distinct, reciprocally monophyletic
Tree TSAR rank	Species	Subspecies	Species	Species	Species

Its most useful morphological feature is the character that gives the species its name. The lower leaf surface carries spreading whitish hairs, while the midrib and stronger secondary veins bear much longer erect hairs, often yellowish to brownish and up to several millimetres long. Similar hairs occur on petioles and peduncles. The overall effect is distinctly velvety rather than the sandpapery feel produced by the short appressed hairs of H. strigosa.

This distinction is not perfect in every mixed population. Plants showing intermediate hair types occur within the broader complex, particularly in Sichuan, demonstrating that indumentum by itself is an imperfect species criterion. What changes the interpretation is that De Smet's molecular analyses recover H. villosa as a coherent evolutionary lineage despite the modest gross morphological differences.

Its precise natural distribution remains a worthwhile research problem. Historical literature emphasizes Sichuan, whereas De Smet sampled convincing H. villosa populations in Hubei. Trees and Shrubs Online accordingly gives Hubei and Sichuan while noting that the true range may be broader. A modern specimen-level revision would be valuable because historical broad-aspera identifications can obscure the distribution of the restored species.

The species currently carries a compact set of associated names, including var. delicatula, f. sterilis, var. strigosior, and var. velutina. These morphological segregates do not presently warrant their own Tree TSAR page entities.

Horticultural and Agricultural Uses

Velvetleaf hydrangea may be more familiar in gardens than its contested botanical status suggests. A substantial proportion of plants historically grown simply as H. aspera fit the villosa phenotype reasonably well, and horticulture has also used the informal designation H. aspera Villosa Group when taxonomic treatments submerged the species.

It is often one of the most garden-friendly members of the complex: comparatively narrow leaves, dense velvety pubescence, smaller flower heads, and a relatively compact habit distinguish many forms. Pinkish or lilac sterile flowers surround purple fertile flowers, and established plants can produce a refined woodland effect without the massive scale of H. sargentiana or some forms of ssp. robusta.

Several notable cultivars are closely associated with this lineage, including ‘Anthony Bullivant’, ‘Sam MacDonald’, and ‘Velvet and Lace’. Their placement should nevertheless remain horticultural rather than being used as proof of wild species boundaries, particularly because seed-raised garden populations can outcross with other members of the complex.

Recognition of H. villosa at species rank improves horticultural curation by giving biologically supported wild material somewhere more informative to reside than an indiscriminate H. aspera catch-all.

Conservation Concerns

No formal IUCN assessment was located for H. villosa. De Smet reported large populations without obvious major threats in the field localities examined, but also emphasized that the geographical distribution was comparatively limited and insufficiently understood.

Distributional uncertainty is therefore the most immediate conservation information gap. If herbarium and observational records have historically been filed under broad H. aspera, the true extent, population number, and regional rarity of H. villosa cannot be inferred reliably from backbone occurrence maps.

Recognition as a species makes provenance-sensitive ex situ conservation more important. Old garden material ultimately descended from a limited number of Wilson introductions may preserve valuable germplasm, but it cannot substitute automatically for representation of contemporary wild populations across Hubei, Sichuan, and any additional confirmed portions of the range.

Additional Information

Plants of the World Online — Hydrangea villosa (opens in a new tab): Plants of the World Online: Current alternative treatment synonymizing H. villosa beneath H. aspera.

Trees and Shrubs Online — Hydrangea villosa (opens in a new tab): Trees and Shrubs Online: Detailed account of morphology, cultivation, garden history, and molecular evidence supporting species recognition.

References and Further Reading

De Smet Y (2020) Through the fog: Evolutionary insights provide novel genus- and species-level boundaries in tribe Hydrangeeae and genus Hydrangea. PhD thesis, Ghent University, Faculty of Sciences, Ghent, Belgium. https://biblio.ugent.be/publication/8716125 (opens in a new tab)

De Smet Y, De Clerck O, Uemachi T, Granados Mendoza C, Wanke S, Goetghebeur P, Samain M-S (2017) Multilocus coalescent species delimitation to evaluate traditionally defined morphotypes in Hydrangea sect. Asperae (Hydrangeaceae). Molecular Phylogenetics and Evolution 114: 415–425. https://doi.org/10.1016/j.ympev.2017.05.021 (opens in a new tab)

Mortreau E, Siljak-Yakovlev S, Cerbah M, Brown SC, Bertrand H, Lambert C (2010) Cytogenetic characterization of Hydrangea involucrata Sieb. and H. aspera D. Don complex (Hydrangeaceae): Genetic, evolutional, and taxonomic implications. Tree Genetics & Genomes 6(1): 137–148. https://doi.org/10.1007/s11295-009-0235-8 (opens in a new tab)

Sutton J (2025) Hydrangea villosa. Trees and Shrubs Online. International Dendrology Society. https://www.treesandshrubsonline.org/articles/hydrangea/hydrangea-villosa/ (opens in a new tab)