Hydrangea japonicavar. variegata (E.J.Lowe & W.Howard) Regel
Hydrangea macrocephala Dippel
Viburnum macrophyllum Thunb.
Close-up on a flowerhead showing the two flower types;Izu Ōshima, near Tokyo, Japan.
Hydrangea macrophylla is a species offlowering plant in thefamilyHydrangeaceae,native andendemic to Japan.[1] It is adeciduousshrub growing to 3 m (10 ft) tall by 2.5 m (8 ft) or more broad with large heads of pink or blue flowers in summer and autumn.[2][3][4] It is currently treated as monotypic, with no subspecies or varieties.[1] Common names includebigleaf hydrangea, and, for particularcultivar groups, the nameslacecap hydrangea,mophead hydrangea, andhortensia.[2] It is widely cultivated in many parts of the world in many climates. It is not to be confused withH. aspera 'Macrophylla'.
Hydrangea macrophylla is endemic to Japan,[1] where it occurs in coastal habitats from Honshu southwards.[5] Natural wild plants, formerly sometimes distinguished asH. macrophylla var.normalis E.H.Wilson,[5] have "lacecap" structure flowerheads, with a few large sterile showy bract-like flowers that act as targets for pollinators, surrounding a central cluster of small fertile flowers. A closely related hydrangea from the mountains of the interior of Japan,Hydrangea serrata, was treated as a variety ofH. macrophylla by some authors in the past,[6] but is currently treated as a separate species.[7]
The termmacrophylla means 'large- or long-leaved'.[10] The opposite leaves can grow to 15 cm (6 in) in length. They are simple, membranous, orbicular to elliptic and acuminate. They are generally serrated.
The naturalinflorescence of wildHydrangea macrophylla is acorymb, with all flowers placed in a plane. Two distinct types of flowers are found; numerous central, small, fertilepentamerous ones, and a few peripheral, large,tetramerous ones; the latter are usually sterile, and whitish to pale blue or pinkish.[5][3] The small flowers have five small greenish sepals and five small petals. Flowering begins in early summer and lasts until early winter. The fruit is a subglobose capsule.
In cultivation as anornamental plant, numerous variants have been developed ascultivars; in most of these (over 500 cultivars), the small central flowers replaced by large, sterile or mostly sterile tetramerous flowers, the inflorescence forming a hemisphere or a whole sphere rather than in a flat plane. These cultivar groups are known as "mophead" or "hortensia" hydrangeas.[2] These large flowers have colours ranging from pale pink to red, fuchsia, purple, to blue. A much smaller cultivar group (over 20 cultivars), known as "lacecap" hydrangeas, retain the natural form of flat flowerheads with small flowers surrounded by a halo of large sterile flowers, but varying from the wild plants in more intense colours.[2] Some cultivars (possibly many, and particularly those selected for greater cold tolerance) derive fromhybrids betweenHydrangea macrophylla andHydrangea serrata, the hill hydrangea of the mountains of Japan.[3]
The flowers ofHydrangea macrophylla cultivars can be blue, red, pink, light purple, or dark purple. The colour is affected bysoil pH.[11][12] An acidic soil (pH below 7) will usually produce a flower colour closer to blue, whereas an alkaline soil (pH above 7) will produce flowers of a pink, or even a red colour.[13] This is caused by a colour change of theflower pigments in the presence ofaluminium ions which can be taken up intohyperaccumulating plants. Scientists do not understand why this happens, whether it is due to predation or to attract pollinators.
The various colours, such as red, mauve, purple, violet and blue, inH. macrophylla are developed from one simple anthocyanin, delphinidin 3-glucoside (myrtillin), which forms complexes with metal ions calledmetalloanthocyanins.[19][20]
Amacha is a Japanese beverage made from fermented leaves ofHydrangea macrophylla var.thunbergii.
Hydrangeae Dulcis Folium is a drug made from the fermented and dried leaves ofH. macrophylla var. thunbergii with possible antiallergic and antimicrobial properties.[22] It also has a hepatoprotective activity by suppression of D-galactosamine-induced liver injury in vitro and in vivo.[23]
Hydrangea macrophylla is included in theTasmanian Fire Service's list of lowflammability plants, indicating that it is suitable for growing within a building protection zone.[24]
Leaf extracts ofHydrangea macrophylla are being investigated as a possible source of new chemical compounds with antimalarial activity.[25][26]Hydrangeic acid from the leaves is being investigated as a possible anti-diabetic drug as it significantly lowered blood glucose, triglyceride, and free fatty acid levels in laboratory animals.[18]
^abcdeHuxley, Antony; Levy, Margot (1992).The New Royal Horticultural Society Dictionary of Gardening. London & New York: MacMillan. p. 610.ISBN0-333-47494-5.
^abcBean, William Jackson; Clarke, D. L. (1981).Trees and Shrubs Hardy in the British Isles. Vol. 2. John Murray Pubs Limited. pp. 391–396.ISBN0-7195-2256-0.
^RHS A-Z encyclopedia of garden plants. United Kingdom: Dorling Kindersley. 2008. p. 1136.ISBN978-1405332965.
^Matsuda, H; Wang, Q; Matsuhira, K; Nakamura, S; Yuan, D; Yoshikawa, M (2008). "Inhibitory effects of thunberginols A and B isolated fromHydrangeae Dulcis Folium on mRNA expression of cytokines and on activation of activator protein-1 in RBL-2H3 cells".Phytomedicine.15 (3):177–84.doi:10.1016/j.phymed.2007.09.010.PMID17950587.
^abZhang, Hailong; Matsuda, Hisashi; Yamashita, Chihiro; Nakamura, Seikou; Yoshikawa, Masayuki (2009). "Hydrangeic acid from the processed leaves ofHydrangea macrophylla var.thunbergii as a new type of anti-diabetic compound".European Journal of Pharmacology.606 (1–3):255–61.doi:10.1016/j.ejphar.2009.01.005.PMID19374876.
^Hayashi, K.; Abe, Y. (1953). "Studien über Anthocyane. XXIII. Papierchromatographische Übersicht der Anthocyane im Pflanzenreich".Miscellaneous Reports of the Research Institute for Natural Resources.29:1–8.
^Kamei K.; Matsuoka H.; Furuhata S.I.; Fujisaki R.I.; Kawakami T.; Mogi S.; Yoshihara H.; Aoki N.; Ishii A.; et al. (2000). "Anti-malarial activity of leaf-extract ofHydrangea macrophylla, a common Japanese plant".Acta Medica Okayama.54 (5):227–232.PMID11061572.
^Yarnell E, Abascal K (Oct 2004). "Botanical treatment and prevention of malaria: Part 2 - Selected botanicals".Alternative and Complementary Therapies.10 (5):277–84.doi:10.1089/act.2004.10.277.
Yuan, Qi, H., Yang, S., Chu, Z., Zhang, G., & Liu, C. (2023). Role of delphinidin-3-glucoside in the sepal blue color change among Hydrangea macrophylla cultivars. Scientia Horticulturae, 313, 111902–.https://doi.org/10.1016/j.scienta.2023.111902
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