八仙花种

绣球花原产于日本，是一种常见的园艺装饰花，花色一般包括红、蓝、紫色，会因所在环境的酸碱度引起花色变化，所以也可作为天然的酸碱指示剂，其在酸性的土壤偏向青色、中性至碱性的土壤则偏向红色。夏季开花，花期5-8月。也常用于制作干花。

原生种是“额紫杨花”（Hydrangea macrophylla f. normalis，日语：ガクアジサイ），以密集而较小型的两性花为中央部分，外围以装饰花（四瓣萼片的不育花）围着。而现时一般所指的园艺观赏用绣球花，都被栽培成只有装饰花的部分，伞房状聚伞花序近球形，外观犹如绣球，狭义上又被称为“本紫阳花”（日语：ホンアジサイ）。

整株植物有毒，茎叶毒性较强。

根据日本绣球花研究者山本武臣之研究，“紫阳花”之称呼最早出自唐朝诗人白居易，可能用以称呼紫丁香；后因平安时代学者源顺误用流传，而成为日本对绣球花的通称。神户市将其作为市花。

花语

感谢、希望、忠贞、永恒、美满及团聚。

Hydrangea macrophylla is a species of flowering plant in the family Hydrangeaceae, native and endemic to Japan. It is a deciduous shrub 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. It is currently treated as monotypic, with no subspecies or varieties. Common names include bigleaf hydrangea, and, for particular cultivar groups, the names lacecap hydrangea, mophead hydrangea, 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'.

Distribution and habitat

Hydrangea macrophylla is endemic to Japan, where it occurs in coastal habitats from Honshu southwards. Natural wild plants, formerly sometimes distinguished as H. macrophylla var. normalis E.H.Wilson, 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 of H. macrophylla by some authors in the past, but is currently treated as a separate species.

The species is naturalised in China, Korea, Siberia, New Zealand and the Americas, and has become an invasive species in the Azores and Madeira archipelagos.

Description

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 natural inflorescence of wild Hydrangea macrophylla is a corymb, with all flowers placed in a plane. Two distinct types of flowers are found; numerous central, small, fertile pentamerous ones, and a few peripheral, large, tetramerous ones; the latter are usually sterile, and whitish to pale blue or pinkish. 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.

Colour and soil acidity

The flowers of Hydrangea macrophylla cultivars can be blue, red, pink, light purple, or dark purple. The colour is affected by soil pH. 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. This is caused by a colour change of the flower pigments in the presence of aluminium ions which can be taken up into hyperaccumulating plants. Scientists do not understand why this happens, whether it is due to predation or to attract pollinators.

Chemistry

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 contain the stilbenoid hydrangeic acid.

The various colours, 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.

Lunularic acid, lunularin, 3,4′-dihydroxystilbene and a glycoside of lunularic acid have been found in the roots of H. macrophylla.

Uses

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.

Hydrangea macrophylla is included in the Tasmanian Fire Service's list of low flammability plants, indicating that it is suitable for growing within a building protection zone.

Leaf extracts of Hydrangea macrophylla are being investigated as a possible source of new chemical compounds with antimalarial activity.

Cultivars

The two main groups of H. macrophylla cultivars are called "lacecap" and "mophead".