Editing Hydrangea (section)

{{Short description|Genus of flowering plants}}
{{Redirect-several|Hydrangea|Hortensia}}
{{Automatic taxobox
|image=Hydrangea arborescens 139866012.jpg
|image_caption=''[[Hydrangea arborescens]]'' in Catoctin Creek Park & Nature Center, Maryland, USA
|taxon=Hydrangea
|authority=[[Jan Frederik Gronovius|Gronov.]] ex [[Carl Linnaeus|L.]]
|subdivision_ranks=Species
|subdivision=See text
|synonyms_ref=<ref name="30010546-2" >{{cite web |url=https://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:30010546-2 |title=''Hydrangea'' Gronov. ex L. |website=Plants of the World Online |publisher=Board of Trustees of the Royal Botanic Gardens, Kew |date=2021 |access-date=17 September 2021 }}</ref>
|synonyms=
{{collapsible list|bullets = true
 |title={{small|synonymy}}
|''Adamia'' {{small|Wall.}}
|''Broussaisia'' {{small|Gaudich.}}
|''Calyptranthe'' {{small|(Maxim.) Nakai}}
|''Cardiandra'' {{small|Siebold & Zucc.}}
|''Cianitis'' {{small|Reinw.}}
|''Cornidia'' {{small|Ruiz & Pav.}}
|''Decumaria'' {{small|L.}}
|''Deinanthe'' {{small|Maxim.}}
|''Dichroa'' {{small|Lour.}}
|× ''Didrangea'' {{small|J.M.H.Shaw}}
|''Forsythia'' {{small|Walter}}
|''Heteromalla'' {{small|(Rehder) H.Ohba & S.Akiyama}}
|''Hortensia'' {{small|Comm. ex Juss.}}
|''Hydrangia'' {{small|L.}}
|''Macnemaraea'' {{small|Willemet}}
|''Pileostegia'' {{small|Hook.f. & Thomson}}
|''Platycrater'' {{small|Siebold & Zucc.}}
|''Sarcostyles'' {{small|C.Presl ex DC.}}
|''Schizophragma'' {{small|Siebold & Zucc.}}
}}
|type_species = ''[[Hydrangea arborescens]]'' L.<ref name = "IPNI">''Hydrangea'' | International Plant Names Index. (n.d.). Retrieved January 5, 2024, from https://www.ipni.org/n/30010546-2</ref>
}}

'''''Hydrangea''''' ({{IPAc-en|h|aɪ|ˈ|d|r|eɪ|n|dʒ|ə}}<ref>{{Cite Cambridge Dictionaries|hydrangea|access-date=15 September 2024}}</ref><ref>{{Cite Merriam-Webster|hydrangea|access-date=15 September 2024}}</ref> or {{IPAc-en|h|aɪ|ˈ|d|r|eɪ|n|dʒ|i|ə}}<ref>''Sunset Western Garden Book'', 1995: 606–607</ref>) is a [[genus]] of more than 70 species of [[Flowering plant|flowering plants]] [[native plant|native]] to Asia and the Americas. '''Hydrangea''' is also used as the [[common name]] for the genus; some (particularly ''[[Hydrangea macrophylla|H. macrophylla]]'') are also often called '''hortensia'''.<ref>{{cite web | title=Hydrangea macrophylla (H) | website=RHS | date=2025-02-04 | url=https://www.rhs.org.uk/plants/40792/hydrangea-macrophylla-(h)/details | access-date=2025-04-23}}</ref> The genus was first described from Virginia in North America,<ref>{{cite book | last=Linné | first=Carl von | last2=Salvius | first2=Lars | title=Caroli Linnaei ... Species plantarum :exhibentes plantas rite cognitas, ad genera relatas, cum differentiis specificis, nominibus trivialibus, synonymis selectis, locis natalibus, secundum systema sexuale digestas... | publisher=Impensis Laurentii Salvii | publication-place=Holmiae | year=1753 | doi=10.5962/bhl.title.669 | doi-access=free | url=https://www.biodiversitylibrary.org/itempdf/13829 | access-date=2025-04-23 | page=}}</ref> but by far the greatest species diversity is in eastern Asia, notably China, Korea, and Japan. Most are [[shrub|shrubs]] {{cvt|1-3|m}} tall, but some are small [[tree]]s, and others [[liana]]s reaching up to {{cvt|30|m|ft|-1}} by climbing up trees. They can be either [[deciduous]] or [[evergreen]], though the widely [[Horticulture|cultivated]] [[Temperate climate|temperate]] species are all deciduous.<ref>{{cite web |title=The United States National Arboretum: Hydrangea FAQ |url=http://www.usna.usda.gov/Gardens/faqs/hydrangeafaq2.html |access-date=27 November 2008 |archive-url=https://web.archive.org/web/20130516083220/http://www.usna.usda.gov/Gardens/faqs/hydrangeafaq2.html |archive-date=16 May 2013 |url-status=dead}}</ref>

The flowers of many hydrangeas act as natural [[pH indicator]]s, producing blue flowers when the soil is acidic and pink ones when the soil is alkaline.<ref>{{Cite web |date=2017-02-06 |title=Curious Chemistry Guides Hydrangea Colors |url=https://www.americanscientist.org/article/curious-chemistry-guides-hydrangea-colors |access-date=2024-05-27 |website=American Scientist |language=en}}</ref>