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Cladus: Eukaryota
Regnum: Plantae
Divisio: Magnoliophyta
Classis: Magnoliopsida
Ordo: Cornales
Familia: Hydrangeaceae
Subfamilia: Hydrangeoideae
Tribus: Hydrangeeae
Genus: Hydrangea
Species: H. anomala - H. arborescens - H. aspera - H. bretschneideri - H. candida - H. caudatifolia - H. chinensis - H. chungii - H. cinerea - H. coacta - H. coenobialis - H. davidii - H. dumicola - H. gracilis - H. heteromalla - H. hirta - H. hypoglauca - H. integrifolia - H. involucrata - H. kawakamii - H. kwangsiensis - H. kwangtungensis - H. lingii - H. linkweiensis - H. longifolia - H. longipes - H. macrocarpa - H. macrophylla - H. mangshanensis - H. paniculata - H. petiolaris - H. quercifolia - H. radiata - H. robusta - H. sargentiana - H. scandens - H. serrata - H. serratifolia - H. stenophylla - H. strigosa - H. stylosa - H. sungpanensis - H. xanthoneura - H. zhewanensis

Name

Hydrangea L.

Vernacular names
Internationalization
Dansk: Hortensia
Deutsch: Hortensien
Ελληνικά: Ορτανσία
Esperanto: Hidrangeo
Français: Hortensia
Magyar: Hortenzia
日本語: アジサイ
Nedersaksisch: Attinsioa
Nederlands: Hortensia
Polski: Hortensja (roślina)
Português: Hortênsia
Русский: Гортензия
Suomi: Hortensiat
Svenska: Hortensiasläktet
ไทย: ไฮเดรนเยีย
Tiếng Việt: Tú cầu
中文: 繡球花

Hydrangea (pronounced /haɪˈdreɪndʒⁱə/,[1] common names Hydrangea and Hortensia) is a genus of about 70 to 75 species of flowering plants native to southern and eastern Asia (China, Japan, Korea, the Himalayas, and Indonesia) and North and South America. By far the greatest species diversity is in eastern Asia, notably China, Japan, and Korea. Most are shrubs 1 to 3 meters tall, but some are small trees, and others lianas reaching up to 30 m by climbing up trees. They can be either deciduous or evergreen, though the widely cultivated temperate species are all deciduous.

Having been introduced to the Azores Islands of Portugal, they are now very common there, particularly on Faial Island, which is known as the "blue island" due to the vast number of hydrangeas present on the island, and on Flores Island.

Species in the related genus Schizophragma, also in Hydrangeaceae, are also often known as hydrangeas. Schizophragma hydrangeoides and Hydrangea petiolaris are both commonly known as climbing hydrangeas.

There are two flower arrangements in hydrangeas. Mophead flowers are large round flowerheads resembling pom-poms or, as the name implies, the head of a mop. In contrast, lacecap flowers bear round, flat flowerheads with a center core of subdued, fertile flowers surrounded by outer rings of showy, sterile flowers.

Life cycle

Hydrangea flowers are produced from early spring to late autumn; they grow in flowerheads (corymbs or panicles) at the ends of the stems. In many species, the flowerheads contain two types of flowers, small fertile flowers in the middle of the flowerhead, and large, sterile bract-like flowers in a ring around the edge of each flowerhead. Other species have all the flowers sterile and of the same size.

Colours and acidity

In most species the flowers are white, but in some species (notably H. macrophylla), can be blue, red, pink, light purple, or dark purple. In these species the exact colour often mirrors the pH of the soil; acidic soils produce blue flowers, neutral soils produce very pale cream petals, and alkaline soils results in pink or purple. 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.[2][3]

Partial list of species

* Hydrangea anomala (Climbing Hydrangea). Himalaya, southwest China.
* Hydrangea arborescens (Smooth Hydrangea). Eastern North America.
* Hydrangea aspera. China, Himalaya.
* Hydrangea bretschneideri. China.
* Hydrangea candida. China.
* Hydrangea caudatifolia. China.
* Hydrangea chinensis. China.
* Hydrangea chungii. China.
* Hydrangea cinerea (Ashy Hydrangea). Eastern United States.
* Hydrangea coacta. China.
* Hydrangea coenobialis. China.
* Hydrangea davidii. China.
* Hydrangea dumicola. China.
* Hydrangea gracilis. China.
* Hydrangea heteromalla. Himalaya, west and north China.
* Hydrangea hirta. Japan.
* Hydrangea hypoglauca. China.
* Hydrangea integrifolia. China.
* Hydrangea involucrata. Japan, Taiwan.
* Hydrangea kawakamii. Taiwan.
* Hydrangea kwangsiensis. China.
* Hydrangea kwangtungensis. China.
* Hydrangea lingii. China.
* Hydrangea linkweiensis. China.
* Hydrangea longifolia. China.
* Hydrangea longipes. Western China.
* Hydrangea macrocarpa. China.
* Hydrangea macrophylla (Bigleaf Hydrangea). Southeast Japan.
* Hydrangea mangshanensis. China.
* Hydrangea paniculata (Panicled Hydrangea). Eastern China, Japan, Korea, Sakhalin.
* Hydrangea petiolaris (Climbing Hydrangea). Japan, Korea, Sakhalin.
* Hydrangea quercifolia (Oakleaf Hydrangea). Southeast United States.
* Hydrangea radiata (Silverleaf Hydrangea). Southeast United States.
* Hydrangea robusta. China, Himalaya.
* Hydrangea sargentiana. Western China.
* Hydrangea scandens. Southern Japan south to the Philippines.
* Hydrangea serrata. Japan, Korea.
* Hydrangea serratifolia. Chile, western Argentina.
* Hydrangea stenophylla. China.
* Hydrangea strigosa. China.
* Hydrangea stylosa. China.
* Hydrangea sungpanensis. China.
* Hydrangea xanthoneura. China.
* Hydrangea zhewanensis. China.


Cultivation and uses

Hydrangeas are popular ornamental plants, grown for their large flowerheads, with Hydrangea macrophylla being by far the most widely grown with over 600 named cultivars, many selected to have only large sterile flowers in the flowerheads. Some are best pruned on an annual basis when the new leaf buds begin to appear. If not pruned regularly, the bush will become very 'leggy', growing upwards until the weight of the stems is greater than their strength, at which point the stems will sag down to the ground and possibly break. Other species only flower on 'old wood'. Thus new wood resulting from pruning will not produce flowers until the following season.

Hydrangeas are moderately toxic if eaten, with all parts of the plant containing cyanogenic glycosides.[4] Hydrangea paniculata is reportedly sometimes smoked as an intoxicant, despite the danger of illness and/or death due to the cyanide.[5]

In Japan, ama-cha, meaning sweet tea, is another herbal tea made from Hydrangea serrata, whose leaves contain a substance that develops a sweet taste (phyllodulcin). For the fullest taste, fresh leaves are crumpled, steamed, and dried, yielding dark brown tea leaves. Ama-cha is mainly used for kan-butsu-e (the Buddha bathing ceremony) on April 8 every year—the day thought to be Buddha's birthday in Japan. Ama-cha is poured over a statue of Buddha in the ceremony and served to people in attendance. A legend has it that on the day Buddha was born, nine dragons poured Amrita over him; ama-cha is substituted for Amrita in Japan.

In Korean tea, Hydrangea serrata (hangul:산수국 hanja:山水菊) is used for a herbal tea called sugukcha (수국차) or ilsulcha (이슬차).

Diseases

Main article: List of hydrangea diseases

References

1. ^ Sunset Western Garden Book, 1995:606–607
2. ^ University of Georgia: Growing Bigleaf Hydrangea
3. ^ USDA: Hydrangea Questions and Answers
4. ^ ASPCA Animal Poison Control Center
5. ^ Erowid Hydrangea Vault

1 http://www.erowid.org/herbs/hydrangea/hydrangea.shtml

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