Hydrangea macrophylla is a species of flowering plant in the family Hydrangeaceae, native to Japan. It is a deciduous shrub growing to 2 m (7 ft) tall by 2.5 m (8 ft) broad with large heads of pink or blue flowers in summer and autumn. Common names include bigleaf hydrangea, French hydrangea, lacecap hydrangea, mophead hydrangea, penny mac and hortensia. It is widely cultivated in many parts of the world in many climates. It is not to be confused with H. aspera 'Macrophylla'.
The term macrophylla means large- or long-leaved. 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 inflorescence of Hydrangea macrophylla is a corymb, with all flowers placed in a plane or a hemisphere or even a whole sphere in cultivated forms. Two distinct types of flowers can be identified: central non-ornamental fertile flowers and peripheral ornamental flowers, usually described as "sterile". A study of several cultivars showed that all the flowers were fertile but the non-ornamental flowers were pentamers while the decorative flowers were tetramers. The four sepals of decorative flowers have colors ranging from pale pink to red fuchsia purple to blue. The non-decorative flowers have five small greenish sepals and five small petals. Flowering lasts from early summer to early winter. The fruit is a subglobose capsule.
Colors and soil acidity
Hydrangea macrophylla blooms can be blue, red, pink, light purple, or dark purple. The color is affected by soil pH. An acidic soil (pH below 7) will usually produce flower color closer to blue, whereas an alkaline soil (pH above 7) will produce flowers more pink. This is caused by a color change of the flower pigments in the presence of aluminium ions which can be taken up into hyperaccumulating plants.
In climates where Hydrangea macrophylla flowers, place in a mixed shrub border or at the back of a flower bed. Its rich foliage and large size make it a wonderful background for white or light colored flowers, even tall growing perennials and annuals. In warm climates H. macrophylla is good for adding a splash of early summer color to shady areas and woodland gardens. Minimal pruning is recommended for most prolific flowering. Flowers are easily air dried and are long lasting.
While Hydrangea macrophylla is not considered a particularly difficult plant to grow, it may fail to flower. This may be due to cold winter damage to the flower buds, not getting enough sunlight, too much nitrogen fertilizer, or pruning at the wrong time of year. H. macrophylla forms flower buds in late summer. As a result, pruning in late summer, fall or winter could remove potential flowers. 
Phyllodulcin, hydrangenol, and their 8-O-glucosides, and thunberginols A and F can be found in H. macrophylla. Thunberginol B, the dihydroisocoumarins thunberginol C, D and E, the dihydroisocoumarin glycosides thunberginol G 3'-O-glucoside and (−)-hydrangenol 4'-O-glucoside and four kaempferol and quercetin oligoglycosides can be found in Hydrangeae Dulcis Folium, the processed leaves of H. macrophylla var. thunbergii. The leaves also contains the stilbenoid hydrangeic acid.
The various colors, such as red, mauve, purple, violet and blue, in H. macrophylla are developed from one simple anthocyanin, delphinidin 3-glucoside (myrtillin), which forms complexes with metal ions called metalloanthocyanins.
Hydrangine is another name for the coumarin umbelliferone, and may be responsible for the possible toxicity of the plant.
Amacha is a Japanese beverage made from fermented leaves of Hydrangea macrophylla var. thunbergii.
Hydrangeae Dulcis Folium is a drug made from the fermented and dried leaves of H. macrophylla var. thunbergii with possible antiallergic and antimicrobial properties. It also has a hepatoprotective activity by suppression of D-galactosamine-induced liver injury in vitro and in vivo.
Leaf extracts of Hydrangea macrophylla are being investigated as a possible source of new chemical compounds with antimalarial activity. 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.
The two main types of H. macrophylla cultivars are called mophead and lacecap. Other types are in different species. 
- 'All Summer Beauty' a cold-hardy, floriferous mophead
- 'Alpengluhen' a deep-red colored mophead
- 'Ami Pasquier' a floriferous, wine pink to blue mophead
- 'Bailmer' (marketed as Endless Summer) a perpetual-blooming, pink to blue mophead
- 'Beaute Vendomoise' a giant whitish-pink lacecap
- 'Blaumeise' agm a Swiss-bred "Teller" blue lacecap
- 'Blue Bonnet' a hardy, blue mophead
- 'Blue Wave' a robust light pink to light blue lacecap
- 'Blushing Bride' a cold-hardy, ever-blooming white mophead
- 'Europa' agm
- 'Forever Pink' a pink mophead
- 'Générale Vicomtesse de Vibraye'agm a cold-hardy, French-bred pink to blue mophead
- 'Hamburg' a deep-colored pink to blue mophead
- 'Harlequin' a picoteed pink to purple mophead
- 'Lanarth White'agm
- 'Lilacina' a cold-hardy, disease-resistant pink to blue lacecap
- ’Love You Kiss agm red-margined white florets, lacecap
- 'Madame Emile Mouillère'agm small shrub to 1.8 m (5.9 ft), white flowers
- 'Marechal Foch' an old-fashioned pink to blue mophead
- 'Mariesii Grandiflora'
- 'Mariesii Lilacina'agm
- 'Mariesii Perfecta'
- 'Nikko Blue' a popular, cold-hardy pink to blue mophead
- 'Pia' a dwarf pink to purplish-blue mophead
- 'Penny Mac' a cold-hardy, pink to blue mophead
- ’Rotschwantz’ agm deep red lacecap
- 'Soeur Therese' a hardy, robust white mophead
- 'Taube' a Swiss-bred "Teller", pink to blue lacecap
- 'Tokyo Delight'agm
- 'Twist-N-Shout an ever-blooming, hardy pink to blue lacecap
- 'Veitchii'agm an exceptionally disease-resistant, sun-tolerant white lacecap
- ’Zorro’ agm lacecap blue
H. m. 'Nikko Blue' petals exhibiting the 'blueing' effects of aluminium sulfate solution
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- "RHS Plant Selector - Hydrangea macrophylla 'Altona'". Retrieved 22 June 2013.
- "RHS Plant Selector - Hydrangea macrophylla 'Ami Pasquier'". Retrieved 22 June 2013.
- "RHS Plantfinder - Hydrangea macrophylla 'Blaumeiser'". Retrieved 7 March 2018.
- "RHS Plant Selector - Hydrangea macrophylla 'Europa'". Retrieved 22 June 2013.
- "RHS Plant Selector - Hydrangea macrophylla 'Générale Vicomtesse de Vibraye'". Retrieved 22 June 2013.
- "RHS Plant Selector - Hydrangea macrophylla 'Lanarth White'". Retrieved 22 June 2013.
- "RHS Plantfinder - Hydrangea macrophylla 'Love You Kiss'". Retrieved 7 March 2018.
- "RHS Plant Selector - Hydrangea macrophylla 'Madame Emile Mouillère'". Retrieved 22 June 2013.
- "RHS Plant Selector - Hydrangea macrophylla 'Mariesii Grandiflora'". Retrieved 22 June 2013.
- "RHS Plant Selector - Hydrangea macrophylla 'Mariesii Lilacina'". Retrieved 22 June 2013.
- "RHS Plant Selector - Hydrangea macrophylla 'Mariesii Perfecta'". Retrieved 22 June 2013.
- "RHS Plant Selector - Hydrangea macrophylla 'Möwe'". Retrieved 22 June 2013.
- "RHS Plant Selector - Hydrangea macrophylla 'Nigra'". Retrieved 22 June 2013.
- "RHS Plantfinder - Hydrangea macrophylla 'Rotschwantz'". Retrieved 7 March 2018.
- "RHS Plant Selector - Hydrangea macrophylla 'Tokyo Delight'". Retrieved 22 June 2013.
- "RHS Plant Selector - Hydrangea macrophylla 'Veitchii'". Retrieved 22 June 2013.
- "RHS Plant Selector - Hydrangea macrophylla 'Westfalen'". Retrieved 22 June 2013.
- "RHS Plantfinder - Hydrangea macrophylla 'Zorro'". Retrieved 7 March 2018.
|Wikimedia Commons has media related to Hydrangea macrophylla.|
|Wikispecies has information related to Hydrangea macrophylla|
- - Splendor In The Grass
- Hydrangeas- Their Pruning and Care(Heronswood Nursery)
- http://www.HydrangeasHydrangeas.com/mopheads.html - All About Hydrangeas: Information on Hydrangea macrophylla.
- Hydrangea Thoughts I - Informative but non-scholarly essay on Hydrangea (Culture, History and Etymology).