Hydrangea cinerea
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Credits
Julian Sutton (2025)
Recommended citation
Sutton, J. (2025), 'Hydrangea cinerea' from the website Trees and Shrubs Online (treesandshrubsonline.
Common Names
- Ashy Hydrangea
Synonyms
- Hydrangea arborescens subsp. discolor (Ser.) E.M.McClint.
- Hydrangea arborescens var. discolor Ser.
- Hydrangea ashei Harb.
Other taxa in genus
- Hydrangea ampla
- Hydrangea angustipetala
- Hydrangea anomala
- Hydrangea arborescens
- Hydrangea arborescens Species Complex Cultivars A–M
- Hydrangea arborescens Species Complex Cultivars N–Z
- Hydrangea aspera
- Hydrangea aspera Species Complex Cultivars
- Hydrangea barbara
- Hydrangea bretschneideri
- Hydrangea daimingshanensis
- Hydrangea davidii
- Hydrangea fauriei
- Hydrangea febrifuga
- Hydrangea glaucescens
- Hydrangea heteromalla
- Hydrangea heteromalla Species Complex Cultivars
- Hydrangea hirsuta
- Hydrangea hirta
- Hydrangea hwangii
- Hydrangea hydrangeoides
- Hydrangea indochinensis
- Hydrangea integrifolia
- Hydrangea Intersectional Hybrids
- Hydrangea involucrata
- Hydrangea kawakamii
- Hydrangea kwangsiensis
- Hydrangea liukiuensis
- Hydrangea lobbii
- Hydrangea longifolia
- Hydrangea longipes
- Hydrangea luteovenosa
- Hydrangea macrophylla
- Hydrangea obtusifolia
- Hydrangea paniculata
- Hydrangea paniculata Cultivars A–D
- Hydrangea paniculata Cultivars E–I
- Hydrangea paniculata Cultivars J–L
- Hydrangea paniculata Cultivars M–R
- Hydrangea paniculata Cultivars S–Z
- Hydrangea petiolaris
- Hydrangea platyarguta
- Hydrangea pottingeri
- Hydrangea quercifolia
- Hydrangea radiata
- Hydrangea robusta
- Hydrangea sargentiana
- Hydrangea scandens
- Hydrangea schizomollis
- Hydrangea Section Macrophyllae Cultivars A
- Hydrangea Section Macrophyllae Cultivars B
- Hydrangea Section Macrophyllae Cultivars C
- Hydrangea Section Macrophyllae Cultivars D
- Hydrangea Section Macrophyllae Cultivars E–F
- Hydrangea Section Macrophyllae Cultivars G
- Hydrangea Section Macrophyllae Cultivars H
- Hydrangea Section Macrophyllae Cultivars I–J
- Hydrangea Section Macrophyllae Cultivars K
- Hydrangea Section Macrophyllae Cultivars L
- Hydrangea Section Macrophyllae Cultivars M
- Hydrangea Section Macrophyllae Cultivars N–O
- Hydrangea Section Macrophyllae Cultivars P–Q
- Hydrangea Section Macrophyllae Cultivars R
- Hydrangea Section Macrophyllae Cultivars S
- Hydrangea Section Macrophyllae Cultivars T–U
- Hydrangea Section Macrophyllae Cultivars V–Z
- Hydrangea seemannii
- Hydrangea serrata
- Hydrangea serratifolia
- Hydrangea sikokiana
- Hydrangea species of Section Cornidia
- Hydrangea species of Sections Cardiandra and Deinanthe
- Hydrangea strigosa
- Hydrangea stylosa
- Hydrangea tomentella
- Hydrangea × versicolor
- Hydrangea viburnoides
- Hydrangea villosa
- Hydrangea xanthoneura
- Hydrangea × ytiensis
Deciduous shrub, 1–3 m. Bark brown or reddish. Branchlets with stiff, spreading or adpressed hairs. Leaves opposite. Leaf blade ovate, (2.5–)4–15 × (1.5–)2–12 cm; base cordate, truncate, or cuneate; margin dentate to serrate; apex acute to acuminate; upper surface green, sparsely hirsute; lower surface greyish and uniformly hairy, either velutinous, pilose, or tomentose; petiole 1–8.5 cm, stiffly hairy. Inflorescence terminal, a much-branched dome-shaped structure 3.5–14.5 × 3–16.5 cm, with 150–500 flowers; sterile flowers present in some individuals; peduncle 0.5–6 cm. Sterile flowers largely consisting of 3–4(–5) large, petaloid sepals, white to greenish, obovate to broadly ovate, round, or elliptic, 0.9–1.5 × 0.2–1.4 cm. Fertile flowers with calyx tube ~1 mm, and very small deltate to triangular calyx lobes; petals white or cream, ~1 mm long, free, falling early; stamens 10, 1.5–4.5 mm, five about twice as long as the others; ovary inferior, with 2(–3) locules; styles 2(–3), distinct, ~1 mm. Fruit a hemispherical capsule, ~2 × 2 mm, dehiscing at the apex between the styles. Seeds brown, <1 mm. Flowering May–July (United States). (Freeman 2016; McClintock 1957).
Distribution United States Central & Southeastern
Habitat Deciduous upland and bottomland forests, shaded cliffs, ravines, streambeds; 100–700 m asl.
USDA Hardiness Zone 5-9
RHS Hardiness Rating H6
Conservation status Not evaluated (NE)
Of the three hardy, deciduous, shrubby species in the Hydrangea arborescens complex, H. cinerea is perhaps the least interesting to gardeners. We discuss it briefly by comparison with the tolerant, well known H. arborescens and the more obviously distinct and rather beautiful H. radiata.
H. cinerea is intermediate between its two relatives in leaf and flower. The leaf underside is greyish hairy, sometimes quite densely, but never matted and silvery white as in H. radiata. Sterile flowers are more often present than in H. arborescens, but not as frequently as in H. cinerea (Freeman 2016; McClintock 1957). H. cinerea has a more restricted range than H. arborescens, centred on the Southern Appalachians, but is more widespread than H. radiata.
The first unambiguous mention of this plant in the scientific literature is by De Candolle (1830) as H. arborescens var. discolor Ser., citing a specimen in French medic/botanist Nicolas Seringe’s herbarium. McClintock (1957) raised it to subspecies level, while Pilatowski (1982) made a strong case for it being a full, reproductively isolated species, usually accepted today. There is a plethora of 19th century names for plants in this complex, many with weak, ambiguous descriptions. Hydrangea discolor Raf. could not be used – from its brief description (Rafinesque 1838), it could well be just a minor variant of H. radiata, so H. cinerea is the valid name, well described with an associated type specimen by Small (1898).
Its main (if still minor) contribution to gardens has been the mophead form ‘Sterilis’, which has been in cultivation since the 19th century (Rehder 1908). Wild type plants are sometimes seen in serious hydrangea collections and botanic gardens (e.g. Arnold Arboretum 2024; Royal Botanic Garden Edinburgh 2024). Some plants grown as H. arborescens might prove to be H. cinerea, and hybridization in gardens is a possibility. Hence we discuss all cultivars in the complex together on alphabetical pages ‘Hydrangea arborescens Species Complex Cultivars A–M’ etc.
